[dm-devel] [RFC PATCH 05/20] libmultipath: don't update path groups when printing

[Martin Wilck]

Updating the prio values for printing makes no sense. The user wants to see
the prio values multipath is actually using for path group selection, and
updating the values here means actually lying to the user if the prio values
have changed, but multipathd hasn't updated them internally.

If we really don't update the pathgroup prios when we need to, this should be
fixed elsewhere. The current wrong output would just hide that if it occured.

Moreover, correctness forbids changing properties so deeply in a code path
that's supposed to print them only. Finally, this piece of code prevents the
print.c code to be converted to proper "const" usage.

Signed-off-by: Martin Wilck 
---
 libmultipath/print.c | 7 ---
 1 file changed, 7 deletions(-)

diff --git a/libmultipath/print.c b/libmultipath/print.c
index 8fb5c5058965..b5c00bfe69a5 100644
--- a/libmultipath/print.c
+++ b/libmultipath/print.c
@@ -484,13 +484,6 @@ snprint_pg_selector (char * buff, size_t len, struct 
pathgroup * pgp)
 static int
 snprint_pg_pri (char * buff, size_t len, struct pathgroup * pgp)
 {
-   /*
-* path group priority is not updated for every path prio change,
-* but only on switch group code path.
-*
-* Printing is another reason to update.
-*/
-   path_group_prio_update(pgp);
return snprint_int(buff, len, pgp->priority);
 }
 
-- 
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[dm-devel] [RFC PATCH 19/20] multipathd: use foreign API

[Martin Wilck]

Call into the foreign library code when paths are discovered, uevents
are received, and in the checker loop. Furthermore, use the foreign
code to print information in the "multipathd show paths", "multipathd
show maps", and "multipathd show topology" client commands.

We don't support foreign data in the individual "show map" and "show path"
commands, and neither in the "json" commands. The former is a deliberate
decision, the latter could be added if desired.

Signed-off-by: Martin Wilck 
---
 libmultipath/discovery.c  |  4 +++-
 multipathd/cli_handlers.c | 39 ++-
 multipathd/main.c | 43 ---
 3 files changed, 77 insertions(+), 9 deletions(-)

diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
index 645224c1029c..45a4d8378893 100644
--- a/libmultipath/discovery.c
+++ b/libmultipath/discovery.c
@@ -31,6 +31,7 @@
 #include "prio.h"
 #include "defaults.h"
 #include "prioritizers/alua_rtpg.h"
+#include "foreign.h"
 
 int
 alloc_path_with_pathinfo (struct config *conf, struct udev_device *udevice,
@@ -1909,7 +1910,8 @@ int pathinfo(struct path *pp, struct config *conf, int 
mask)
 * limited by DI_BLACKLIST and occurs before this debug
 * message with the mask value.
 */
-   if (pp->udev && filter_property(conf, pp->udev) > 0)
+   if (pp->udev && (is_claimed_by_foreign(pp->udev) ||
+filter_property(conf, pp->udev) > 0))
return PATHINFO_SKIPPED;
 
if (filter_devnode(conf->blist_devnode,
diff --git a/multipathd/cli_handlers.c b/multipathd/cli_handlers.c
index 78f2a12bc2f8..c0ae54aae841 100644
--- a/multipathd/cli_handlers.c
+++ b/multipathd/cli_handlers.c
@@ -27,6 +27,7 @@
 #include "main.h"
 #include "cli.h"
 #include "uevent.h"
+#include "foreign.h"
 
 int
 show_paths (char ** r, int * len, struct vectors * vecs, char * style,
@@ -35,11 +36,13 @@ show_paths (char ** r, int * len, struct vectors * vecs, 
char * style,
int i;
struct path * pp;
char * c;
-   char * reply;
+   char * reply, * header;
unsigned int maxlen = INITIAL_REPLY_LEN;
int again = 1;
 
get_path_layout(vecs->pathvec, 1);
+   foreign_path_layout();
+
reply = MALLOC(maxlen);
 
while (again) {
@@ -48,18 +51,29 @@ show_paths (char ** r, int * len, struct vectors * vecs, 
char * style,
 
c = reply;
 
-   if (pretty && VECTOR_SIZE(vecs->pathvec) > 0)
+   if (pretty)
c += snprint_path_header(c, reply + maxlen - c,
 style);
+   header = c;
 
vector_foreach_slot(vecs->pathvec, pp, i)
c += snprint_path(c, reply + maxlen - c,
  style, pp, pretty);
 
+   c += snprint_foreign_paths(c, reply + maxlen - c,
+  style, pretty);
+
again = ((c - reply) == (maxlen - 1));
 
REALLOC_REPLY(reply, again, maxlen);
}
+
+   if (pretty && c == header) {
+   /* No output - clear header */
+   *reply = '\0';
+   c = reply;
+   }
+
*r = reply;
*len = (int)(c - reply + 1);
return 0;
@@ -134,6 +148,8 @@ show_maps_topology (char ** r, int * len, struct vectors * 
vecs)
int again = 1;
 
get_path_layout(vecs->pathvec, 0);
+   foreign_path_layout();
+
reply = MALLOC(maxlen);
 
while (again) {
@@ -150,11 +166,13 @@ show_maps_topology (char ** r, int * len, struct vectors 
* vecs)
c += snprint_multipath_topology(c, reply + maxlen - c,
mpp, 2);
}
+   c += snprint_foreign_topology(c, reply + maxlen - c, 2);
 
again = ((c - reply) == (maxlen - 1));
 
REALLOC_REPLY(reply, again, maxlen);
}
+
*r = reply;
*len = (int)(c - reply + 1);
return 0;
@@ -499,12 +517,14 @@ show_maps (char ** r, int *len, struct vectors * vecs, 
char * style,
 {
int i;
struct multipath * mpp;
-   char * c;
+   char * c, *header;
char * reply;
unsigned int maxlen = INITIAL_REPLY_LEN;
int again = 1;
 
get_multipath_layout(vecs->mpvec, 1);
+   foreign_multipath_layout();
+
reply = MALLOC(maxlen);
 
while (again) {
@@ -512,9 +532,10 @@ show_maps (char ** r, int *len, struct vectors * vecs, 
char * style,
return 1;
 
c = reply;
-   if (pretty && VECTOR_SIZE(vecs->mpvec) > 0)
+   if (pretty)
c += snprint_multipath_header(c, reply + maxlen - c,
  style);
+   header = c;
 

[dm-devel] [RFC PATCH 20/20] libmultipath: foreign/nvme: implement path display

[Martin Wilck]

implement display of path information for NVMe foreign paths and maps.
With this patch, I get output like this for Linux NVMe soft targets:

multipathd show topology
sys0:NQN:subsysname (uuid.96926ba3-b207-437c-902c-4a4df6538c3f) [nvme] nvme0n1 
NVMe,Linux,4.15.0-r
size=2097152 features='n/a' hwhandler='n/a' wp=rw
`-+- policy='n/a' prio=n/a status=n/a
  |- 0:1:1 nvme0c1n1 0:0 n/a n/a live
  |- 0:2:1 nvme0c2n1 0:0 n/a n/a live
  |- 0:3:1 nvme0c3n1 0:0 n/a n/a live
  `- 0:4:1 nvme0c4n1 0:0 n/a n/a live

multipathd show paths format '%G %d %i %o %z %m %N'
foreign dev   hcil  dev_st serial   multipath host WWNN
[nvme]  nvme0c1n1 0:1:1 live   1c2c86659503a02f nvme0n1   
rdma:traddr=192.168.201.101,trsvcid=4420
[nvme]  nvme0c2n1 0:2:1 live   1c2c86659503a02f nvme0n1   
rdma:traddr=192.168.202.101,trsvcid=4420
[nvme]  nvme0c3n1 0:3:1 live   1c2c86659503a02f nvme0n1   
rdma:traddr=192.168.203.101,trsvcid=4420
[nvme]  nvme0c4n1 0:4:1 live   1c2c86659503a02f nvme0n1   
rdma:traddr=192.168.204.101,trsvcid=4420

(admittedly, I abused the 'WWNN' wildcard here a bit to display information
which is helpful for NVMe over RDMA).

Signed-off-by: Martin Wilck 
---
 libmultipath/foreign/nvme.c | 342 ++--
 1 file changed, 327 insertions(+), 15 deletions(-)

diff --git a/libmultipath/foreign/nvme.c b/libmultipath/foreign/nvme.c
index 4e9c3a52d03c..5546a8eb178a 100644
--- a/libmultipath/foreign/nvme.c
+++ b/libmultipath/foreign/nvme.c
@@ -25,42 +25,97 @@
 #include 
 #include 
 #include 
+#include 
+#include 
 #include "vector.h"
 #include "generic.h"
 #include "foreign.h"
 #include "debug.h"
+#include "structs.h"
+#include "sysfs.h"
 
+static const char nvme_vendor[] = "NVMe";
+static const char N_A[] = "n/a";
 const char *THIS;
 
+struct nvme_map;
+struct nvme_path {
+   struct gen_path gen;
+   struct udev_device *udev;
+   struct udev_device *ctl;
+   struct nvme_map *map;
+   bool seen;
+};
+
+struct nvme_pathgroup {
+   struct gen_pathgroup gen;
+   vector pathvec;
+};
+
 struct nvme_map {
struct gen_multipath gen;
struct udev_device *udev;
struct udev_device *subsys;
dev_t devt;
+   /* Just one static pathgroup for NVMe for now */
+   struct nvme_pathgroup pg;
+   struct gen_pathgroup *gpg;
+   struct _vector pgvec;
+   vector pathvec;
+   int nr_live;
 };
 
-#define NAME_LEN 64 /* buffer length temp model name */
+#define NAME_LEN 64 /* buffer length for temp attributes */
 #define const_gen_mp_to_nvme(g) ((const struct nvme_map*)(g))
 #define gen_mp_to_nvme(g) ((struct nvme_map*)(g))
 #define nvme_mp_to_gen(n) &((n)->gen)
+#define const_gen_pg_to_nvme(g) ((const struct nvme_pathgroup*)(g))
+#define gen_pg_to_nvme(g) ((struct nvme_pathgroup*)(g))
+#define nvme_pg_to_gen(n) &((n)->gen)
+#define const_gen_path_to_nvme(g) ((const struct nvme_path*)(g))
+#define gen_path_to_nvme(g) ((struct nvme_path*)(g))
+#define nvme_path_to_gen(n) &((n)->gen)
+
+static void cleanup_nvme_path(struct nvme_path *path)
+{
+   condlog(5, "%s: %p %p", __func__, path, path->udev);
+   if (path->udev)
+   udev_device_unref(path->udev);
+   /* ctl is implicitly referenced by udev, no need to unref */
+   free(path);
+}
 
 static void cleanup_nvme_map(struct nvme_map *map)
 {
+   if (map->pathvec) {
+   struct nvme_path *path;
+   int i;
+
+   vector_foreach_slot_backwards(map->pathvec, path, i) {
+   condlog(5, "%s: %d %p", __func__, i, path);
+   cleanup_nvme_path(path);
+   vector_del_slot(map->pathvec, i);
+   }
+   }
+   vector_free(map->pathvec);
if (map->udev)
udev_device_unref(map->udev);
-   if (map->subsys)
-   udev_device_unref(map->subsys);
+   /* subsys is implicitly referenced by udev, no need to unref */
free(map);
 }
 
 static const struct _vector*
 nvme_mp_get_pgs(const struct gen_multipath *gmp) {
-   return NULL;
+   const struct nvme_map *nvme = const_gen_mp_to_nvme(gmp);
+
+   /* This is all used under the lock, no need to copy */
+   return >pgvec;
 }
 
 static void
 nvme_mp_rel_pgs(const struct gen_multipath *gmp, const struct _vector *v)
 {
+   /* empty */
 }
 
 static void rstrip(char *str)
@@ -75,7 +130,6 @@ static int snprint_nvme_map(const struct gen_multipath *gmp,
char *buff, int len, char wildcard)
 {
const struct nvme_map *nvm = const_gen_mp_to_nvme(gmp);
-   static const char nvme_vendor[] = "NVMe";
char fld[NAME_LEN];
const char *val;
 
@@ -92,6 +146,8 @@ static int snprint_nvme_map(const struct gen_multipath *gmp,
return snprintf(buff, len, "%s",
udev_device_get_sysattr_value(nvm->udev,

[dm-devel] [RFC PATCH 12/20] libmultipath: "generic multipath" interface

[Martin Wilck]

This patch adds a simplified abstract interface to the multipath data 
structures.
The idea is to allow "foreign" data structures to be treated by libmultipath
if they implement the same interface. Currently, the intention is to use this
only to provide formatted output about from this interface.

This interface assumes only that the data structure is organized in maps
containing path groups containing paths, and that formatted printing (using
the wildcards defined in libmultipath) is possible on each level of the data
structure.

The patch also implements the interface for the internal dm_multipath data
structure.

The style() method looks a bit exotic, but it's necessary because
print_multipath_topology() uses different formats depending on the mpp
properties. This needs to be in the generic interface, too, if we want to
produce identical output.

Signed-off-by: Martin Wilck 
---
 libmultipath/Makefile |   2 +-
 libmultipath/dm-generic.c |  70 
 libmultipath/dm-generic.h |  41 ++
 libmultipath/generic.c|  39 +
 libmultipath/generic.h| 136 ++
 libmultipath/list.h   |   4 ++
 libmultipath/print.c  |  34 
 libmultipath/print.h  |   7 +++
 libmultipath/structs.c|   4 ++
 libmultipath/structs.h|   4 ++
 10 files changed, 340 insertions(+), 1 deletion(-)
 create mode 100644 libmultipath/dm-generic.c
 create mode 100644 libmultipath/dm-generic.h
 create mode 100644 libmultipath/generic.c
 create mode 100644 libmultipath/generic.h

diff --git a/libmultipath/Makefile b/libmultipath/Makefile
index 25b052729d48..0099d9d6cc39 100644
--- a/libmultipath/Makefile
+++ b/libmultipath/Makefile
@@ -43,7 +43,7 @@ OBJS = memory.o parser.o vector.o devmapper.o callout.o \
switchgroup.o uxsock.o print.o alias.o log_pthread.o \
log.o configure.o structs_vec.o sysfs.o prio.o checkers.o \
lock.o waiter.o file.o wwids.o prioritizers/alua_rtpg.o prkey.o \
-   io_err_stat.o
+   io_err_stat.o dm-generic.o generic.o
 
 all: $(LIBS)
 
diff --git a/libmultipath/dm-generic.c b/libmultipath/dm-generic.c
new file mode 100644
index ..42a26085d087
--- /dev/null
+++ b/libmultipath/dm-generic.c
@@ -0,0 +1,70 @@
+/*
+  Copyright (c) 2018 Martin Wilck, SUSE Linux GmbH
+
+  This program is free software; you can redistribute it and/or
+  modify it under the terms of the GNU General Public License
+  as published by the Free Software Foundation; either version 2
+  of the License, or (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
+  USA.
+ */
+
+#include 
+#include 
+#include "generic.h"
+#include "dm-generic.h"
+#include "structs.h"
+#include "structs_vec.h"
+#include "config.h"
+#include "print.h"
+
+static const struct _vector*
+dm_mp_get_pgs(const struct gen_multipath *gmp)
+{
+   return vector_convert(NULL, gen_multipath_to_dm(gmp)->pg,
+ struct pathgroup, dm_pathgroup_to_gen);
+}
+
+static void dm_mp_rel_pgs(const struct gen_multipath *gmp,
+ const struct _vector* v)
+{
+   vector_free_const(v);
+}
+
+static const struct _vector*
+dm_pg_get_paths(const struct gen_pathgroup *gpg)
+{
+   return vector_convert(NULL, gen_pathgroup_to_dm(gpg)->paths,
+ struct path, dm_path_to_gen);
+}
+
+static void dm_mp_rel_paths(const struct gen_pathgroup *gpg,
+   const struct _vector* v)
+{
+   vector_free_const(v);
+}
+
+const struct gen_multipath_ops dm_gen_multipath_ops = {
+   .get_pathgroups = dm_mp_get_pgs,
+   .rel_pathgroups = dm_mp_rel_pgs,
+   .snprint = snprint_multipath_attr,
+   /* .style = snprint_multipath_style, TBD */
+};
+
+const struct gen_pathgroup_ops dm_gen_pathgroup_ops = {
+   .get_paths = dm_pg_get_paths,
+   .rel_paths = dm_mp_rel_paths,
+   .snprint = snprint_pathgroup_attr,
+};
+
+const struct gen_path_ops dm_gen_path_ops = {
+   .snprint = snprint_path_attr,
+};
diff --git a/libmultipath/dm-generic.h b/libmultipath/dm-generic.h
new file mode 100644
index ..5d5972406819
--- /dev/null
+++ b/libmultipath/dm-generic.h
@@ -0,0 +1,41 @@
+/*
+  Copyright (c) 2018 Martin Wilck, SUSE Linux GmbH
+
+  This program is free software; you can redistribute it and/or
+  modify it under the terms of the GNU General Public License
+  as published by the Free Software Foundation; either version 2
+  of the License, or (at your option) any later version.

[dm-devel] [RFC PATCH 01/20] multipath(d)/Makefile: add explicit dependency on libraries

[Martin Wilck]

Otherwise the binaries won't be re-linked if the libraries change.

Signed-off-by: Martin Wilck 
---
 multipath/Makefile  | 2 +-
 multipathd/Makefile | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/multipath/Makefile b/multipath/Makefile
index 654568af3576..0828a8f72db7 100644
--- a/multipath/Makefile
+++ b/multipath/Makefile
@@ -14,7 +14,7 @@ OBJS = main.o
 
 all: $(EXEC)
 
-$(EXEC): $(OBJS)
+$(EXEC): $(OBJS) $(multipathdir)/libmultipath.so $(mpathcmddir)/libmpathcmd.so
$(CC) $(CFLAGS) $(OBJS) -o $(EXEC) $(LDFLAGS) $(LIBDEPS)
$(GZIP) $(EXEC).8 > $(EXEC).8.gz
$(GZIP) $(EXEC).conf.5 > $(EXEC).conf.5.gz
diff --git a/multipathd/Makefile b/multipathd/Makefile
index 251690ec5e2a..4c9d29634160 100644
--- a/multipathd/Makefile
+++ b/multipathd/Makefile
@@ -28,7 +28,7 @@ EXEC = multipathd
 
 all : $(EXEC)
 
-$(EXEC): $(OBJS)
+$(EXEC): $(OBJS) $(multipathdir)/libmultipath.so $(mpathcmddir)/libmpathcmd.so
$(CC) $(CFLAGS) $(OBJS) $(LDFLAGS) -o $(EXEC) $(LIBDEPS)
$(GZIP) $(EXEC).8 > $(EXEC).8.gz
 
-- 
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[dm-devel] [RFC PATCH 09/20] multipath-tools: Makefile.inc: use -Werror=cast-qual

[Martin Wilck]

Casting "const" away is often an indicator for wrong code.
Add a compiler flag to warn about such possible breakage.

Signed-off-by: Martin Wilck 
---
 Makefile.inc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Makefile.inc b/Makefile.inc
index eb99c36010c1..a5b9d4e3fa74 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -87,6 +87,7 @@ STACKPROT := $(call 
TEST_CC_OPTION,-fstack-protector-strong,-fstack-protector)
 OPTFLAGS   = -O2 -g -pipe -Wall -Wextra -Wformat=2 -Werror=implicit-int \
  -Werror=implicit-function-declaration -Werror=format-security 
\
  -Wno-sign-compare -Wno-unused-parameter -Wno-clobbered \
+ -Werror=cast-qual -Werror=discarded-qualifiers \
  -Wp,-D_FORTIFY_SOURCE=2 $(STACKPROT) \
  --param=ssp-buffer-size=4
 
-- 
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[dm-devel] [RFC PATCH 13/20] libmultipath: print: convert API to generic data type

[Martin Wilck]

Convert higher level API (snprint_multipath_topology() etc) to
using the generic multipath API. This will allow "foreign"
multipath objects that implement the generic API to be printed
exactly like native multipathd objects.

The previous API (using "struct multipath*" and "struct path" remains
in place through macros mapping to the new functions. By doing this
and testing in regular setups, it's easily verified that the new
API works and produces the same results.

Moreover, abstract out the code to determine the output format from multipath
properties into snprint_multipath_style(), to be able to use it as generic
->style() method.

Signed-off-by: Martin Wilck 
---
 libmultipath/configure.c  |   1 +
 libmultipath/dm-generic.c |   2 +-
 libmultipath/print.c  | 116 +-
 libmultipath/print.h  |  28 ---
 multipath/main.c  |   1 +
 multipathd/cli_handlers.c |   1 +
 6 files changed, 100 insertions(+), 49 deletions(-)

diff --git a/libmultipath/configure.c b/libmultipath/configure.c
index 13e14cc25fff..42b7c896ee65 100644
--- a/libmultipath/configure.c
+++ b/libmultipath/configure.c
@@ -30,6 +30,7 @@
 #include "discovery.h"
 #include "debug.h"
 #include "switchgroup.h"
+#include "dm-generic.h"
 #include "print.h"
 #include "configure.h"
 #include "pgpolicies.h"
diff --git a/libmultipath/dm-generic.c b/libmultipath/dm-generic.c
index 42a26085d087..bdc9ca0a488b 100644
--- a/libmultipath/dm-generic.c
+++ b/libmultipath/dm-generic.c
@@ -56,7 +56,7 @@ const struct gen_multipath_ops dm_gen_multipath_ops = {
.get_pathgroups = dm_mp_get_pgs,
.rel_pathgroups = dm_mp_rel_pgs,
.snprint = snprint_multipath_attr,
-   /* .style = snprint_multipath_style, TBD */
+   .style = snprint_multipath_style,
 };
 
 const struct gen_pathgroup_ops dm_gen_pathgroup_ops = {
diff --git a/libmultipath/print.c b/libmultipath/print.c
index e6f56381791f..8846765066ef 100644
--- a/libmultipath/print.c
+++ b/libmultipath/print.c
@@ -31,7 +31,8 @@
 #include "discovery.h"
 #include "dm-generic.h"
 
-#define MAX(x,y) (x > y) ? x : y
+#define MAX(x,y) (((x) > (y)) ? (x) : (y))
+#define MIN(x,y) (((x) > (y)) ? (y) : (x))
 #define TAIL (line + len - 1 - c)
 #define NOPADs = c
 #define PAD(x) \
@@ -846,8 +847,8 @@ snprint_multipath_header (char * line, int len, const char 
* format)
 }
 
 int
-snprint_multipath (char * line, int len, const char * format,
-const struct multipath * mpp, int pad)
+_snprint_multipath (const struct gen_multipath * gmp,
+   char * line, int len, const char * format, int pad)
 {
char * c = line;   /* line cursor */
char * s = line;   /* for padding */
@@ -870,7 +871,7 @@ snprint_multipath (char * line, int len, const char * 
format,
if (!(data = mpd_lookup(*f)))
continue;
 
-   data->snprint(buff, MAX_FIELD_LEN, mpp);
+   gmp->ops->snprint(gmp, buff, MAX_FIELD_LEN, *f);
PRINT(c, TAIL, "%s", buff);
if (pad)
PAD(data->width);
@@ -913,8 +914,8 @@ snprint_path_header (char * line, int len, const char * 
format)
 }
 
 int
-snprint_path (char * line, int len, const char * format,
-const struct path * pp, int pad)
+_snprint_path (const struct gen_path * gp, char * line, int len,
+  const char * format, int pad)
 {
char * c = line;   /* line cursor */
char * s = line;   /* for padding */
@@ -937,7 +938,7 @@ snprint_path (char * line, int len, const char * format,
if (!(data = pd_lookup(*f)))
continue;
 
-   data->snprint(buff, MAX_FIELD_LEN, pp);
+   gp->ops->snprint(gp, buff, MAX_FIELD_LEN, *f);
PRINT(c, TAIL, "%s", buff);
if (pad)
PAD(data->width);
@@ -948,8 +949,8 @@ snprint_path (char * line, int len, const char * format,
 }
 
 int
-snprint_pathgroup (char * line, int len, char * format,
-  const struct pathgroup * pgp)
+_snprint_pathgroup (const struct gen_pathgroup * ggp, char * line, int len,
+   char * format)
 {
char * c = line;   /* line cursor */
char * s = line;   /* for padding */
@@ -972,7 +973,7 @@ snprint_pathgroup (char * line, int len, char * format,
if (!(data = pgd_lookup(*f)))
continue;
 
-   data->snprint(buff, MAX_FIELD_LEN, pgp);
+   ggp->ops->snprint(ggp, buff, MAX_FIELD_LEN, *f);
PRINT(c, TAIL, "%s", buff);
PAD(data->width);
} while (*f++);
@@ -980,8 +981,10 @@ snprint_pathgroup (char * line, int len, char * format,
__endline(line, len, c);
return (c - line);
 }
+#define snprint_pathgroup(line, len, fmt, pgp) \
+   _snprint_pathgroup(dm_pathgroup_to_gen(pgp), line, len, fmt)
 
-void 

[dm-devel] [RFC PATCH 06/20] libmultipath/print: use "const" where appropriate

[Martin Wilck]

Convert the print.h/print.c code to use "const" qualifiers
properly. This is generally considered good programming practice,
and the printing code shouldn't change any objects anyway.

Signed-off-by: Martin Wilck 
---
 libmultipath/configure.h |   1 -
 libmultipath/discovery.c |   6 +--
 libmultipath/discovery.h |   6 ++-
 libmultipath/print.c | 133 ---
 libmultipath/print.h |  41 ---
 5 files changed, 95 insertions(+), 92 deletions(-)

diff --git a/libmultipath/configure.h b/libmultipath/configure.h
index 0ffc28efdaf7..0f5d30a540ca 100644
--- a/libmultipath/configure.h
+++ b/libmultipath/configure.h
@@ -35,5 +35,4 @@ int coalesce_paths (struct vectors *vecs, vector curmp, char 
* refwwid, int forc
 int get_refwwid (enum mpath_cmds cmd, char * dev, enum devtypes dev_type,
 vector pathvec, char **wwid);
 int reload_map(struct vectors *vecs, struct multipath *mpp, int refresh, int 
is_daemon);
-int sysfs_get_host_adapter_name(struct path *pp, char *adapter_name);
 struct udev_device *get_udev_device(const char *dev, enum devtypes dev_type);
diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
index 88e9f3b61510..98bddee52c8f 100644
--- a/libmultipath/discovery.c
+++ b/libmultipath/discovery.c
@@ -401,7 +401,7 @@ sysfs_get_tgt_nodename (struct path *pp, char * node)
return 0;
 }
 
-int sysfs_get_host_adapter_name(struct path *pp, char *adapter_name)
+int sysfs_get_host_adapter_name(const struct path *pp, char *adapter_name)
 {
int proto_id;
 
@@ -427,7 +427,7 @@ int sysfs_get_host_adapter_name(struct path *pp, char 
*adapter_name)
return sysfs_get_host_pci_name(pp, adapter_name);
 }
 
-int sysfs_get_host_pci_name(struct path *pp, char *pci_name)
+int sysfs_get_host_pci_name(const struct path *pp, char *pci_name)
 {
struct udev_device *hostdev, *parent;
char host_name[HOST_NAME_LEN];
@@ -466,7 +466,7 @@ int sysfs_get_host_pci_name(struct path *pp, char *pci_name)
return 1;
 }
 
-int sysfs_get_iscsi_ip_address(struct path *pp, char *ip_address)
+int sysfs_get_iscsi_ip_address(const struct path *pp, char *ip_address)
 {
struct udev_device *hostdev;
char host_name[HOST_NAME_LEN];
diff --git a/libmultipath/discovery.h b/libmultipath/discovery.h
index bd5e6678a26d..9aacf75bfeb0 100644
--- a/libmultipath/discovery.h
+++ b/libmultipath/discovery.h
@@ -44,8 +44,10 @@ int store_pathinfo (vector pathvec, struct config *conf,
struct path **pp_ptr);
 int sysfs_set_scsi_tmo (struct multipath *mpp, int checkint);
 int sysfs_get_timeout(struct path *pp, unsigned int *timeout);
-int sysfs_get_host_pci_name(struct path *pp, char *pci_name);
-int sysfs_get_iscsi_ip_address(struct path *pp, char *ip_address);
+int sysfs_get_host_pci_name(const struct path *pp, char *pci_name);
+int sysfs_get_iscsi_ip_address(const struct path *pp, char *ip_address);
+int sysfs_get_host_adapter_name(const struct path *pp,
+   char *adapter_name);
 ssize_t sysfs_get_vpd (struct udev_device * udev, int pg, unsigned char * buff,
   size_t len);
 int sysfs_get_asymmetric_access_state(struct path *pp,
diff --git a/libmultipath/print.c b/libmultipath/print.c
index b5c00bfe69a5..594ca567e22a 100644
--- a/libmultipath/print.c
+++ b/libmultipath/print.c
@@ -28,6 +28,7 @@
 #include "devmapper.h"
 #include "uevent.h"
 #include "debug.h"
+#include "discovery.h"
 
 #define MAX(x,y) (x > y) ? x : y
 #define TAIL (line + len - 1 - c)
@@ -97,7 +98,7 @@ snprint_size (char * buff, size_t len, unsigned long long 
size)
  * multipath info printing functions
  */
 static int
-snprint_name (char * buff, size_t len, struct multipath * mpp)
+snprint_name (char * buff, size_t len, const struct multipath * mpp)
 {
if (mpp->alias)
return snprintf(buff, len, "%s", mpp->alias);
@@ -106,7 +107,7 @@ snprint_name (char * buff, size_t len, struct multipath * 
mpp)
 }
 
 static int
-snprint_sysfs (char * buff, size_t len, struct multipath * mpp)
+snprint_sysfs (char * buff, size_t len, const struct multipath * mpp)
 {
if (mpp->dmi)
return snprintf(buff, len, "dm-%i", mpp->dmi->minor);
@@ -115,7 +116,7 @@ snprint_sysfs (char * buff, size_t len, struct multipath * 
mpp)
 }
 
 static int
-snprint_ro (char * buff, size_t len, struct multipath * mpp)
+snprint_ro (char * buff, size_t len, const struct multipath * mpp)
 {
if (!mpp->dmi)
return snprintf(buff, len, "undef");
@@ -154,7 +155,7 @@ out:
 }
 
 static int
-snprint_failback (char * buff, size_t len, struct multipath * mpp)
+snprint_failback (char * buff, size_t len, const struct multipath * mpp)
 {
if (mpp->pgfailback == -FAILBACK_IMMEDIATE)
return snprintf(buff, len, "immediate");
@@ -169,7 +170,7 @@ snprint_failback (char * buff, size_t len, struct multipath 
* mpp)
 }
 
 static int

[dm-devel] [RFC PATCH 17/20] libmultipath/foreign: nvme foreign library

[Martin Wilck]

This still contains stubs for path handling and checking, but it's functional
for printing already.

Signed-off-by: Martin Wilck 
---
 Makefile  |   1 +
 libmultipath/foreign/Makefile |  30 +++
 libmultipath/foreign/nvme.c   | 444 ++
 3 files changed, 475 insertions(+)
 create mode 100644 libmultipath/foreign/Makefile
 create mode 100644 libmultipath/foreign/nvme.c

diff --git a/Makefile b/Makefile
index 11c46eb4dbc9..4b145c593605 100644
--- a/Makefile
+++ b/Makefile
@@ -7,6 +7,7 @@ BUILDDIRS = \
libmultipath \
libmultipath/prioritizers \
libmultipath/checkers \
+   libmultipath/foreign \
libmpathpersist \
multipath \
multipathd \
diff --git a/libmultipath/foreign/Makefile b/libmultipath/foreign/Makefile
new file mode 100644
index ..dfba11e86d76
--- /dev/null
+++ b/libmultipath/foreign/Makefile
@@ -0,0 +1,30 @@
+#
+# Copyright (C) 2003 Christophe Varoqui, 
+#
+include ../../Makefile.inc
+
+CFLAGS += $(LIB_CFLAGS) -I..
+
+# If you add or remove a checker also update multipath/multipath.conf.5
+LIBS= \
+   libforeign-nvme.so
+
+all: $(LIBS)
+
+libforeign-%.so: %.o
+   $(CC) $(LDFLAGS) $(SHARED_FLAGS) -o $@ $^
+
+install:
+   $(INSTALL_PROGRAM) -m 755 $(LIBS) $(DESTDIR)$(libdir)
+
+uninstall:
+   for file in $(LIBS); do $(RM) $(DESTDIR)$(libdir)/$$file; done
+
+clean: dep_clean
+   $(RM) core *.a *.o *.gz *.so
+
+OBJS := $(LIBS:libforeign-%.so=%.o)
+include $(wildcard $(OBJS:.o=.d))
+
+dep_clean:
+   $(RM) $(OBJS:.o=.d)
diff --git a/libmultipath/foreign/nvme.c b/libmultipath/foreign/nvme.c
new file mode 100644
index ..4e9c3a52d03c
--- /dev/null
+++ b/libmultipath/foreign/nvme.c
@@ -0,0 +1,444 @@
+/*
+  Copyright (c) 2018 Martin Wilck, SUSE Linux GmbH
+
+  This program is free software; you can redistribute it and/or
+  modify it under the terms of the GNU General Public License
+  as published by the Free Software Foundation; either version 2
+  of the License, or (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
+  USA.
+*/
+
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include "vector.h"
+#include "generic.h"
+#include "foreign.h"
+#include "debug.h"
+
+const char *THIS;
+
+struct nvme_map {
+   struct gen_multipath gen;
+   struct udev_device *udev;
+   struct udev_device *subsys;
+   dev_t devt;
+};
+
+#define NAME_LEN 64 /* buffer length temp model name */
+#define const_gen_mp_to_nvme(g) ((const struct nvme_map*)(g))
+#define gen_mp_to_nvme(g) ((struct nvme_map*)(g))
+#define nvme_mp_to_gen(n) &((n)->gen)
+
+static void cleanup_nvme_map(struct nvme_map *map)
+{
+   if (map->udev)
+   udev_device_unref(map->udev);
+   if (map->subsys)
+   udev_device_unref(map->subsys);
+   free(map);
+}
+
+static const struct _vector*
+nvme_mp_get_pgs(const struct gen_multipath *gmp) {
+   return NULL;
+}
+
+static void
+nvme_mp_rel_pgs(const struct gen_multipath *gmp, const struct _vector *v)
+{
+}
+
+static void rstrip(char *str)
+{
+   int n;
+
+   for (n = strlen(str) - 1; n >= 0 && str[n] == ' '; n--);
+   str[n+1] = '\0';
+}
+
+static int snprint_nvme_map(const struct gen_multipath *gmp,
+   char *buff, int len, char wildcard)
+{
+   const struct nvme_map *nvm = const_gen_mp_to_nvme(gmp);
+   static const char nvme_vendor[] = "NVMe";
+   char fld[NAME_LEN];
+   const char *val;
+
+   switch (wildcard) {
+   case 'd':
+   return snprintf(buff, len, "%s",
+   udev_device_get_sysname(nvm->udev));
+   case 'n':
+   return snprintf(buff, len, "%s:NQN:%s",
+   udev_device_get_sysname(nvm->subsys),
+   udev_device_get_sysattr_value(nvm->subsys,
+ "subsysnqn"));
+   case 'w':
+   return snprintf(buff, len, "%s",
+   udev_device_get_sysattr_value(nvm->udev,
+ "wwid"));
+   case 'S':
+   return snprintf(buff, len, "%s",
+   udev_device_get_sysattr_value(nvm->udev,
+ "size"));
+   case 'v':
+   return snprintf(buff, len, "%s", 

[dm-devel] [RFC PATCH 07/20] libmultipath: use "const" in devmapper code

[Martin Wilck]

Improve use of "const" qualifiers in libmultipath's devmapper code.

Signed-off-by: Martin Wilck 
---
 libmultipath/devmapper.c | 32 
 libmultipath/devmapper.h | 16 
 2 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/libmultipath/devmapper.c b/libmultipath/devmapper.c
index f112e1cb0e66..f61838cbe369 100644
--- a/libmultipath/devmapper.c
+++ b/libmultipath/devmapper.c
@@ -583,7 +583,7 @@ is_mpath_part(const char *part_name, const char *map_name)
return 0;
 }
 
-int dm_get_status(char *name, char *outstatus)
+int dm_get_status(const char *name, char *outstatus)
 {
int r = 1;
struct dm_task *dmt;
@@ -807,7 +807,7 @@ int _dm_flush_map (const char * mapname, int need_sync, int 
deferred_remove,
if (need_suspend &&
!dm_get_map(mapname, , params) &&
strstr(params, "queue_if_no_path")) {
-   if (!dm_queue_if_no_path((char *)mapname, 0))
+   if (!dm_queue_if_no_path(mapname, 0))
queue_if_no_path = 1;
else
/* Leave queue_if_no_path alone if unset failed */
@@ -850,7 +850,7 @@ int _dm_flush_map (const char * mapname, int need_sync, int 
deferred_remove,
} while (retries-- > 0);
 
if (queue_if_no_path == 1)
-   dm_queue_if_no_path((char *)mapname, 1);
+   dm_queue_if_no_path(mapname, 1);
 
return 1;
 }
@@ -938,7 +938,7 @@ out:
 }
 
 int
-dm_fail_path(char * mapname, char * path)
+dm_fail_path(const char * mapname, char * path)
 {
char message[32];
 
@@ -949,7 +949,7 @@ dm_fail_path(char * mapname, char * path)
 }
 
 int
-dm_reinstate_path(char * mapname, char * path)
+dm_reinstate_path(const char * mapname, char * path)
 {
char message[32];
 
@@ -960,7 +960,7 @@ dm_reinstate_path(char * mapname, char * path)
 }
 
 int
-dm_queue_if_no_path(char *mapname, int enable)
+dm_queue_if_no_path(const char *mapname, int enable)
 {
char *message;
 
@@ -973,7 +973,7 @@ dm_queue_if_no_path(char *mapname, int enable)
 }
 
 static int
-dm_groupmsg (char * msg, char * mapname, int index)
+dm_groupmsg (const char * msg, const char * mapname, int index)
 {
char message[32];
 
@@ -984,19 +984,19 @@ dm_groupmsg (char * msg, char * mapname, int index)
 }
 
 int
-dm_switchgroup(char * mapname, int index)
+dm_switchgroup(const char * mapname, int index)
 {
return dm_groupmsg("switch", mapname, index);
 }
 
 int
-dm_enablegroup(char * mapname, int index)
+dm_enablegroup(const char * mapname, int index)
 {
return dm_groupmsg("enable", mapname, index);
 }
 
 int
-dm_disablegroup(char * mapname, int index)
+dm_disablegroup(const char * mapname, int index)
 {
return dm_groupmsg("disable", mapname, index);
 }
@@ -1080,7 +1080,7 @@ out:
 }
 
 int
-dm_geteventnr (char *name)
+dm_geteventnr (const char *name)
 {
struct dm_info info;
 
@@ -1139,7 +1139,7 @@ dm_mapname(int major, int minor)
 
map = dm_task_get_name(dmt);
if (map && strlen(map))
-   response = STRDUP((char *)dm_task_get_name(dmt));
+   response = STRDUP((const char *)dm_task_get_name(dmt));
 
dm_task_destroy(dmt);
return response;
@@ -1264,7 +1264,7 @@ cancel_remove_partmap (const char *name, void *unused)
 }
 
 static int
-dm_get_deferred_remove (char * mapname)
+dm_get_deferred_remove (const char * mapname)
 {
struct dm_info info;
 
@@ -1412,10 +1412,10 @@ out:
return r;
 }
 
-void dm_reassign_deps(char *table, char *dep, char *newdep)
+void dm_reassign_deps(char *table, const char *dep, const char *newdep)
 {
-   char *p, *n;
-   char *newtable;
+   char *n;
+   const char *p, *newtable;
 
newtable = strdup(table);
if (!newtable)
diff --git a/libmultipath/devmapper.h b/libmultipath/devmapper.h
index 558e6914074f..8c8ea6c29b27 100644
--- a/libmultipath/devmapper.h
+++ b/libmultipath/devmapper.h
@@ -38,7 +38,7 @@ int dm_addmap_create (struct multipath *mpp, char *params);
 int dm_addmap_reload (struct multipath *mpp, char *params, int flush);
 int dm_map_present (const char *);
 int dm_get_map(const char *, unsigned long long *, char *);
-int dm_get_status(char *, char *);
+int dm_get_status(const char *, char *);
 int dm_type(const char *, char *);
 int dm_is_mpath(const char *);
 int _dm_flush_map (const char *, int, int, int, int);
@@ -49,14 +49,14 @@ int dm_flush_map_nopaths(const char * mapname, int 
deferred_remove);
_dm_flush_map(mapname, 1, 0, 1, retries)
 int dm_cancel_deferred_remove(struct multipath *mpp);
 int dm_flush_maps (int retries);
-int dm_fail_path(char * mapname, char * path);
-int dm_reinstate_path(char * mapname, char * path);
-int dm_queue_if_no_path(char *mapname, int enable);
-int dm_switchgroup(char * mapname, int index);
-int dm_enablegroup(char * mapname, int index);
-int dm_disablegroup(char * mapname, int index);

[dm-devel] [RFC PATCH 00/20] "Foreign" NVMe support for multipath-tools

[Martin Wilck]

Hello Christophe,

This patch series adds limited support for "foreign" multipath devices
to multipath and multipathd, and implements the respective API for
"native" NVMe multipath devices. The implementation is done using
a shared library approach similar to checkers, so other non-dm multipath
implementations could hook into this API easily.

"Limited support" means here that multipath and multipathd are able
to print information about "foreign" multipath maps with the commands
"multipath -l[l]", "multipathd show topology", "multipathd show maps", and
"multipathd show paths", and that multipathd checks the devices in the
checker loop and prints log messages if something interesting is detected.
No support for other functionality such real health monitoring or
administration is currently planned, although it might be be doable
by extending the code from this patch set.

Sample output from multipathd with this patch set:

multipathd show topology
sys0:NQN:subsysname (uuid.96926ba3-b207-437c-902c-4a4df6538c3f) [nvme] nvme0n1 
NVMe,Linux,4.15.0-r
size=2097152 features='n/a' hwhandler='n/a' wp=rw
`-+- policy='n/a' prio=n/a status=n/a
  |- 0:1:1 nvme0c1n1 0:0 n/a n/a live
  |- 0:2:1 nvme0c2n1 0:0 n/a n/a live
  |- 0:3:1 nvme0c3n1 0:0 n/a n/a live
  `- 0:4:1 nvme0c4n1 0:0 n/a n/a live

The first part of the set (01/20-09/20) consists only of cleanup patches, 
improving the
usage of "const" qualifiers in the part of the code I've been working with.
(I'm routinely trying to do at least some cleanup work when I look more deeply
into parts of the code). These patches don't change functionality. 10/20 and
11/20 are two minor helpers for the patches that follow.

Patch 12/20 and 15/20 represent the actual new APIs. Patch 13, 14 change the
libmultipath printing code to work with the strongly simplified "generic"
multipath API from patch 12/20. This allows to provide foreign library code
without replicating the complex data structures libmultipath is using
internally, and yet use libmultipath's native printing code for displaying
map and path properties.

Patch 15/20 defines the actual API for "foreign" libraries. It is built on
top of the "generic" API which defines the data structures with which objects
like multipath maps and paths are described.

Patch 17/20 and 20/20 provide the implementation of NVMe native multipath
support using these APIs. Patch 18/20 and 19/20 contain the necessary changes
to multipath and multipathd to call into the new APIs.

The patch set is based on the previous multipath-tools patches I
sent to dm-devel:
 - "[PATCH v2 00/20] Various multipath-tools fixes" ff.
 - "[PATCH 0/7] multipath-tools: uevent processing fixes and unit tests" ff.
   (7/7 replaced by "[PATCH v2] multipathd: ignore uevents for non-mpath
   devices")
 - "[PATCH 1/3] multipath.rules: handle NVME devices" ff.
 - "[PATCH] libmultipath: increase path product_id/rev field size for NVMe"

To try and reduce confusion, the full series is available here:
https://github.com/openSUSE/multipath-tools/tree/upstream-queue

Reviews and comments are of course welcome.

Best Regards,
Martin

Martin Wilck (20):
  multipath(d)/Makefile: add explicit dependency on libraries
  libmultipath: remove unused "stdout helpers"
  libmultipath: get rid of selector "hack" in print.c
  libmultipath: parser: use call-by-value for "snprint" methods
  libmultipath: don't update path groups when printing
  libmultipath/print: use "const" where appropriate
  libmultipath: use "const" in devmapper code
  libmultipath: fix compiler warnings for -Wcast-qual
  multipath-tools: Makefile.inc: use -Werror=cast-qual
  libmultipath: add vector_free_const()
  libmultipath: add vector_convert()
  libmultipath: "generic multipath" interface
  libmultipath: print: convert API to generic data type
  libmultipath: print: use generic API for get_x_layout()
  libmultipath: API for foreign multipath handling
  libmultipath/print: add "%G - foreign" wildcard
  libmultipath/foreign: nvme foreign library
  multipath: use foreign API
  multipathd: use foreign API
  libmultipath: foreign/nvme: implement path display

 Makefile  |   1 +
 Makefile.inc  |   1 +
 kpartx/devmapper.c|   3 +-
 libmpathcmd/mpath_cmd.c   |   2 +-
 libmultipath/Makefile |   2 +-
 libmultipath/checkers/rbd.c   |   4 +-
 libmultipath/configure.c  |   1 +
 libmultipath/configure.h  |   1 -
 libmultipath/devmapper.c  |  35 +-
 libmultipath/devmapper.h  |  16 +-
 libmultipath/dict.c   | 206 ++--
 libmultipath/discovery.c  |  22 +-
 libmultipath/discovery.h  |   6 +-
 libmultipath/dm-generic.c |  70 
 libmultipath/dm-generic.h |  41 +++
 libmultipath/dmparser.c   |   2 +-
 libmultipath/foreign.c| 471 ++
 libmultipath/foreign.h| 322 ++
 libmultipath/foreign/Makefile |  30 ++
 libmultipath/foreign/nvme.c   | 756 

[dm-devel] [RFC PATCH 04/20] libmultipath: parser: use call-by-value for "snprint" methods

[Martin Wilck]

Convert the snprint methods for all keywords to call-by-value,
and use "const" qualifier for the "data" argument. This makes sure
that "snprint" type functions don't modify the data they're print,
helps compile-time correctness checking, and allows more proper
"const" cleanups in the future.

Signed-off-by: Martin Wilck 
---
 libmultipath/dict.c   | 206 --
 libmultipath/parser.c |   9 ++-
 libmultipath/parser.h |  12 ++-
 3 files changed, 112 insertions(+), 115 deletions(-)

diff --git a/libmultipath/dict.c b/libmultipath/dict.c
index e52f1f798f7a..47dc2a38f1ac 100644
--- a/libmultipath/dict.c
+++ b/libmultipath/dict.c
@@ -92,46 +92,35 @@ set_yes_no_undef(vector strvec, void *ptr)
 }
 
 static int
-print_int (char *buff, int len, void *ptr)
+print_int (char *buff, int len, long v)
 {
-   int *int_ptr = (int *)ptr;
-   return snprintf(buff, len, "%i", *int_ptr);
+   return snprintf(buff, len, "%li", v);
 }
 
 static int
-print_nonzero (char *buff, int len, void *ptr)
+print_nonzero (char *buff, int len, long v)
 {
-   int *int_ptr = (int *)ptr;
-   if (!*int_ptr)
-   return 0;
-   return snprintf(buff, len, "%i", *int_ptr);
+   return snprintf(buff, len, "%li", v);
 }
 
 static int
-print_str (char *buff, int len, void *ptr)
+print_str (char *buff, int len, const char *ptr)
 {
-   char **str_ptr = (char **)ptr;
-   if (!*str_ptr)
-   return 0;
-   return snprintf(buff, len, "\"%s\"", *str_ptr);
+   return snprintf(buff, len, "\"%s\"", ptr);
 }
 
 static int
-print_yes_no (char *buff, int len, void *ptr)
+print_yes_no (char *buff, int len, long v)
 {
-   int *int_ptr = (int *)ptr;
return snprintf(buff, len, "\"%s\"",
-   (*int_ptr == YN_NO)? "no" : "yes");
+   (v == YN_NO)? "no" : "yes");
 }
 
 static int
-print_yes_no_undef (char *buff, int len, void *ptr)
+print_yes_no_undef (char *buff, int len, long v)
 {
-   int *int_ptr = (int *)ptr;
-   if (!*int_ptr)
-   return 0;
return snprintf(buff, len, "\"%s\"",
-   (*int_ptr == YNU_NO)? "no" : "yes");
+   (v == YNU_NO)? "no" : "yes");
 }
 
 #define declare_def_handler(option, function)  \
@@ -143,29 +132,32 @@ def_ ## option ## _handler (struct config *conf, vector 
strvec)   \
 
 #define declare_def_snprint(option, function)  \
 static int \
-snprint_def_ ## option (struct config *conf, char * buff, int len, void * 
data) \
+snprint_def_ ## option (struct config *conf, char * buff, int len, \
+   const void * data)  \
 {  \
-   return function (buff, len, >option); \
+   return function (buff, len, conf->option);  \
 }
 
 #define declare_def_snprint_defint(option, function, value)\
 static int \
-snprint_def_ ## option (struct config *conf, char * buff, int len, void * 
data) \
+snprint_def_ ## option (struct config *conf, char * buff, int len, \
+   const void * data)  \
 {  \
int i = value;  \
if (!conf->option)  \
-   return function (buff, len, );\
-   return function (buff, len, >option); \
+   return function (buff, len, i); \
+   return function (buff, len, conf->option);  \
 }
 
 #define declare_def_snprint_defstr(option, function, value)\
 static int \
-snprint_def_ ## option (struct config *conf, char * buff, int len, void * 
data) \
+snprint_def_ ## option (struct config *conf, char * buff, int len, \
+   const void * data)  \
 {  \
-   char *s = value;\
+   static const char *s = value;   \
if (!conf->option)  \
-   return function (buff, len, );\
-   return function (buff, len, >option); \
+   return function (buff, len, s); \
+   return function (buff, len, conf->option);  \
 }
 
 #define declare_hw_handler(option, function)   \
@@ -180,10 

[dm-devel] [RFC PATCH 14/20] libmultipath: print: use generic API for get_x_layout()

[Martin Wilck]

Introduce new functions _get_path_layout and _get_multipath_layout
using the new "generic" API to determine field widths, and map the
old API to them.

Furthermore, replace the boolean "header" by an enum with 3 possible
values. The new value LAYOUT_RESET_NOT allows calling the get_x_layout
function several times and determine the overall field width.

Signed-off-by: Martin Wilck 
---
 libmultipath/print.c | 73 
 libmultipath/print.h |  8 ++
 2 files changed, 65 insertions(+), 16 deletions(-)

diff --git a/libmultipath/print.c b/libmultipath/print.c
index 8846765066ef..9a5a6a2f4ad6 100644
--- a/libmultipath/print.c
+++ b/libmultipath/print.c
@@ -698,20 +698,48 @@ snprint_wildcards (char * buff, int len)
 }
 
 void
-get_path_layout (vector pathvec, int header)
+get_path_layout(vector pathvec, int header)
+{
+   vector gpvec = vector_convert(NULL, pathvec, struct path,
+ dm_path_to_gen);
+   _get_path_layout(gpvec,
+header ? LAYOUT_RESET_HEADER : LAYOUT_RESET_ZERO);
+   vector_free(gpvec);
+}
+
+static void
+reset_width(int *width, enum layout_reset reset, const char *header)
+{
+   switch (reset) {
+   case LAYOUT_RESET_HEADER:
+   *width = strlen(header);
+   break;
+   case LAYOUT_RESET_ZERO:
+   *width = 0;
+   break;
+   default:
+   /* don't reset */
+   break;
+   }
+}
+
+void
+_get_path_layout (const struct _vector *gpvec, enum layout_reset reset)
 {
int i, j;
char buff[MAX_FIELD_LEN];
-   struct path * pp;
+   const struct gen_path *gp;
 
for (j = 0; pd[j].header; j++) {
-   if (header)
-   pd[j].width = strlen(pd[j].header);
-   else
-   pd[j].width = 0;
 
-   vector_foreach_slot (pathvec, pp, i) {
-   pd[j].snprint(buff, MAX_FIELD_LEN, pp);
+   reset_width([j].width, reset, pd[j].header);
+
+   if (gpvec == NULL)
+   continue;
+
+   vector_foreach_slot (gpvec, gp, i) {
+   gp->ops->snprint(gp, buff, MAX_FIELD_LEN,
+pd[j].wildcard);
pd[j].width = MAX(pd[j].width, strlen(buff));
}
}
@@ -727,22 +755,35 @@ reset_multipath_layout (void)
 }
 
 void
-get_multipath_layout (vector mpvec, int header)
+get_multipath_layout (vector mpvec, int header) {
+   vector gmvec = vector_convert(NULL, mpvec, struct multipath,
+ dm_multipath_to_gen);
+   _get_multipath_layout(gmvec,
+header ? LAYOUT_RESET_HEADER : LAYOUT_RESET_ZERO);
+   vector_free(gmvec);
+}
+
+void
+_get_multipath_layout (const struct _vector *gmvec,
+   enum layout_reset reset)
 {
int i, j;
char buff[MAX_FIELD_LEN];
-   struct multipath * mpp;
+   const struct gen_multipath * gm;
 
for (j = 0; mpd[j].header; j++) {
-   if (header)
-   mpd[j].width = strlen(mpd[j].header);
-   else
-   mpd[j].width = 0;
 
-   vector_foreach_slot (mpvec, mpp, i) {
-   mpd[j].snprint(buff, MAX_FIELD_LEN, mpp);
+   reset_width([j].width, reset, mpd[j].header);
+
+   if (gmvec == NULL)
+   continue;
+
+   vector_foreach_slot (gmvec, gm, i) {
+   gm->ops->snprint(gm, buff, MAX_FIELD_LEN,
+mpd[j].wildcard);
mpd[j].width = MAX(mpd[j].width, strlen(buff));
}
+   condlog(4, "%s: width %d", mpd[j].header, mpd[j].width);
}
 }
 
diff --git a/libmultipath/print.h b/libmultipath/print.h
index e71f87722315..1ba364ac19ac 100644
--- a/libmultipath/print.h
+++ b/libmultipath/print.h
@@ -93,7 +93,15 @@ struct pathgroup_data {
int (*snprint)(char * buff, size_t len, const struct pathgroup * pgp);
 };
 
+enum layout_reset {
+   LAYOUT_RESET_NOT,
+   LAYOUT_RESET_ZERO,
+   LAYOUT_RESET_HEADER,
+};
+
+void _get_path_layout (const struct _vector *gpvec, enum layout_reset);
 void get_path_layout (vector pathvec, int header);
+void _get_multipath_layout (const struct _vector *gmvec, enum layout_reset);
 void get_multipath_layout (vector mpvec, int header);
 int snprint_path_header (char *, int, const char *);
 int snprint_multipath_header (char *, int, const char *);
-- 
2.16.1

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel

[dm-devel] [RFC PATCH 15/20] libmultipath: API for foreign multipath handling

[Martin Wilck]

Add an API for "foreign" multipaths. Foreign libraries are loaded
from ${multipath_dir}/libforeign-*.so, as we do for checkers.

Refer to "foreign.h" for details about the API itself. Like we do for
checkers, high-level multipath code isn't supposed to call the API directly,
but rather the wrapper functions declared in "foreign.h".

This API is used only for displaying information and for logging. An extension 
to
other functionality (such as monitoring or administration) might be feasible,
but is not planned.

Foreign libraries communicate with libmultipath through the API defined in
"foreign.h". The foreign library can implement multipath maps, pathgroups,
and paths as it likes, they just need to provide the simple interfaces
defined in "generic.h" to libmultipath. These interfaces are used in 
libmultipath's
"print" implementation to convey various bits of information to users. By
using the same interfaces for printing that libmultipath uses internally,
foreign library implementations can focus on the technical side without
worrying about output formatting compatibility.

Signed-off-by: Martin Wilck 
---
 libmultipath/Makefile  |   2 +-
 libmultipath/foreign.c | 471 +
 libmultipath/foreign.h | 322 +
 3 files changed, 794 insertions(+), 1 deletion(-)
 create mode 100644 libmultipath/foreign.c
 create mode 100644 libmultipath/foreign.h

diff --git a/libmultipath/Makefile b/libmultipath/Makefile
index 0099d9d6cc39..806aaa24f84e 100644
--- a/libmultipath/Makefile
+++ b/libmultipath/Makefile
@@ -43,7 +43,7 @@ OBJS = memory.o parser.o vector.o devmapper.o callout.o \
switchgroup.o uxsock.o print.o alias.o log_pthread.o \
log.o configure.o structs_vec.o sysfs.o prio.o checkers.o \
lock.o waiter.o file.o wwids.o prioritizers/alua_rtpg.o prkey.o \
-   io_err_stat.o dm-generic.o generic.o
+   io_err_stat.o dm-generic.o generic.o foreign.o
 
 all: $(LIBS)
 
diff --git a/libmultipath/foreign.c b/libmultipath/foreign.c
new file mode 100644
index ..f429e2759df3
--- /dev/null
+++ b/libmultipath/foreign.c
@@ -0,0 +1,471 @@
+/*
+  Copyright (c) 2018 Martin Wilck, SUSE Linux GmbH
+
+  This program is free software; you can redistribute it and/or
+  modify it under the terms of the GNU General Public License
+  as published by the Free Software Foundation; either version 2
+  of the License, or (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
+  USA.
+*/
+
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include 
+#include "vector.h"
+#include "debug.h"
+#include "util.h"
+#include "foreign.h"
+#include "structs.h"
+#include "structs_vec.h"
+#include "print.h"
+
+static vector foreigns;
+
+#define get_dlsym(foreign, sym, lbl)   \
+   do {\
+   foreign->sym =  dlsym(foreign->handle, #sym);   \
+   if (foreign->sym == NULL) { \
+   condlog(0, "%s: symbol \"%s\" not found in \"%s\"", \
+   __func__, #sym, foreign->name); \
+   goto lbl;   \
+   }   \
+   } while(0)
+
+static void free_foreign(struct foreign **fgn)
+{
+   if (fgn == NULL || *fgn == NULL)
+   return;
+   if ((*fgn)->context != NULL)
+   (*fgn)->cleanup((*fgn)->context);
+   if ((*fgn)->handle != NULL)
+   dlclose((*fgn)->handle);
+   free(*fgn);
+}
+
+void cleanup_foreign(void)
+{
+   struct foreign *fgn;
+   int i;
+
+   vector_foreach_slot(foreigns, fgn, i)
+   free_foreign();
+   vector_free(foreigns);
+   foreigns = NULL;
+}
+
+int init_foreign(const char *multipath_dir)
+{
+   char pathbuf[PATH_MAX];
+   static const char base[] = "libforeign-";
+   static const char suffix[] = ".so";
+   glob_t globbuf;
+   int ret = -EINVAL, r, i;
+
+   if (foreigns != NULL) {
+   condlog(0, "%s: already initialized", __func__);
+   return -EEXIST;
+   }
+   foreigns = vector_alloc();
+
+   if (snprintf(pathbuf, sizeof(pathbuf), "%s/%s*%s",
+multipath_dir, base, suffix) >= sizeof(pathbuf)) {
+   condlog(1, "%s: path length overflow", __func__);
+ 

[dm-devel] [RFC PATCH 03/20] libmultipath: get rid of selector "hack" in print.c

[Martin Wilck]

By properly linking the path groups with their parent multipath,
we don't need this "hack" any more.

Signed-off-by: Martin Wilck 
---
 libmultipath/dmparser.c   |  2 +-
 libmultipath/pgpolicies.c | 11 ++-
 libmultipath/print.c  |  6 +++---
 libmultipath/structs.c| 10 ++
 libmultipath/structs.h|  3 ++-
 5 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/libmultipath/dmparser.c b/libmultipath/dmparser.c
index 027ae989781e..783c934f1154 100644
--- a/libmultipath/dmparser.c
+++ b/libmultipath/dmparser.c
@@ -267,7 +267,7 @@ int disassemble_map(vector pathvec, char *params, struct 
multipath *mpp,
if (!pgp)
goto out;
 
-   if (store_pathgroup(mpp->pg, pgp))
+   if (add_pathgroup(mpp, pgp))
goto out;
 
p += get_word(p, );
diff --git a/libmultipath/pgpolicies.c b/libmultipath/pgpolicies.c
index 4ae4afbccdb7..ac2596ada442 100644
--- a/libmultipath/pgpolicies.c
+++ b/libmultipath/pgpolicies.c
@@ -120,7 +120,7 @@ int group_by_node_name(struct multipath * mp)
if (!pgp)
goto out1;
 
-   if (store_pathgroup(mp->pg, pgp))
+   if (add_pathgroup(mp, pgp))
goto out2;
 
/* feed the first path */
@@ -196,7 +196,7 @@ int group_by_serial(struct multipath * mp)
if (!pgp)
goto out1;
 
-   if (store_pathgroup(mp->pg, pgp))
+   if (add_pathgroup(mp, pgp))
goto out2;
 
/* feed the first path */
@@ -254,7 +254,7 @@ int one_path_per_group(struct multipath *mp)
if (!pgp)
goto out;
 
-   if (store_pathgroup(mp->pg, pgp))
+   if (add_pathgroup(mp, pgp))
goto out1;
 
if (store_path(pgp->paths, pp))
@@ -293,7 +293,7 @@ int one_group(struct multipath *mp) /* aka multibus */
 
vector_free(pgp->paths);
 
-   if (store_pathgroup(mp->pg, pgp))
+   if (add_pathgroup(mp, pgp))
goto out1;
 
pgp->paths = mp->paths;
@@ -367,8 +367,9 @@ int group_by_prio(struct multipath *mp)
if (i < VECTOR_SIZE(mp->pg)) {
if (!vector_insert_slot(mp->pg, i, pgp))
goto out2;
+   pgp->mpp = mp;
} else {
-   if (store_pathgroup(mp->pg, pgp))
+   if (add_pathgroup(mp, pgp))
goto out2;
}
 
diff --git a/libmultipath/print.c b/libmultipath/print.c
index 27636c35e5ff..8fb5c5058965 100644
--- a/libmultipath/print.c
+++ b/libmultipath/print.c
@@ -476,7 +476,9 @@ snprint_pri (char * buff, size_t len, struct path * pp)
 static int
 snprint_pg_selector (char * buff, size_t len, struct pathgroup * pgp)
 {
-   return snprint_str(buff, len, pgp->selector);
+   const char *s = pgp->mpp->selector;
+
+   return snprint_str(buff, len, s ? s : "");
 }
 
 static int
@@ -1030,7 +1032,6 @@ int snprint_multipath_topology(char *buff, int len, 
struct multipath *mpp,
 
vector_foreach_slot (mpp->pg, pgp, j) {
f=fmt;
-   pgp->selector = mpp->selector; /* hack */
if (j + 1 < VECTOR_SIZE(mpp->pg)) {
strcpy(f, "|-+- " PRINT_PG_INDENT);
} else
@@ -1122,7 +1123,6 @@ snprint_multipath_fields_json (char * buff, int len,
 
vector_foreach_slot (mpp->pg, pgp, i) {
 
-   pgp->selector = mpp->selector;
fwd += snprint_pathgroup(buff + fwd, len - fwd, 
PRINT_JSON_GROUP, pgp);
if (fwd >= len)
return fwd;
diff --git a/libmultipath/structs.c b/libmultipath/structs.c
index 4caad2a40302..1ade1a6705ad 100644
--- a/libmultipath/structs.c
+++ b/libmultipath/structs.c
@@ -318,6 +318,16 @@ store_pathgroup (vector pgvec, struct pathgroup * pgp)
return 0;
 }
 
+int add_pathgroup(struct multipath *mpp, struct pathgroup *pgp)
+{
+   int ret = store_pathgroup(mpp->pg, pgp);
+
+   if (ret)
+   return ret;
+   pgp->mpp = mpp;
+   return 0;
+}
+
 int
 store_hostgroup(vector hostgroupvec, struct host_group * hgp)
 {
diff --git a/libmultipath/structs.h b/libmultipath/structs.h
index b951c7b0e157..71b37cc20674 100644
--- a/libmultipath/structs.h
+++ b/libmultipath/structs.h
@@ -340,7 +340,7 @@ struct pathgroup {
int priority;
int enabled_paths;
vector paths;
-   char * selector;
+   struct multipath *mpp;
 };
 
 struct adapter_group {
@@ -379,6 +379,7 @@ int store_hostgroup(vector hostgroupvec, struct host_group 
*hgp);
 
 int store_path (vector pathvec, struct path * pp);
 int store_pathgroup (vector pgvec, struct pathgroup * pgp);
+int 

[dm-devel] [RFC PATCH 08/20] libmultipath: fix compiler warnings for -Wcast-qual

[Martin Wilck]

Fix the warnings that were caused by adding the -Wcast-qual compiler
flag in the previous patch.

Signed-off-by: Martin Wilck 
---
 kpartx/devmapper.c  |  3 ++-
 libmpathcmd/mpath_cmd.c |  2 +-
 libmultipath/checkers/rbd.c |  4 ++--
 libmultipath/devmapper.c|  3 ++-
 libmultipath/discovery.c| 12 ++--
 libmultipath/list.h |  4 ++--
 libmultipath/memory.h   |  8 +++-
 libmultipath/structs.c  |  2 +-
 libmultipath/structs.h  |  2 +-
 libmultipath/uevent.c   |  6 +++---
 libmultipath/util.c |  6 +++---
 multipathd/main.c   | 10 +-
 12 files changed, 35 insertions(+), 27 deletions(-)

diff --git a/kpartx/devmapper.c b/kpartx/devmapper.c
index 4469fa848de8..eb9dac639175 100644
--- a/kpartx/devmapper.c
+++ b/kpartx/devmapper.c
@@ -11,6 +11,7 @@
 #include 
 #include "devmapper.h"
 
+#define FREE_CONST(p) do { free((void*)(long)p); p = NULL; } while(0)
 #define _UUID_PREFIX "part"
 #define UUID_PREFIX _UUID_PREFIX "%d-"
 #define _UUID_PREFIX_LEN (sizeof(_UUID_PREFIX) - 1)
@@ -695,7 +696,7 @@ int dm_find_part(const char *parent, const char *delim, int 
part,
} else
*part_uuid = uuid;
 out:
-   free((void*)tmp);
+   FREE_CONST(tmp);
return r;
 }
 
diff --git a/libmpathcmd/mpath_cmd.c b/libmpathcmd/mpath_cmd.c
index af618cff917c..29d148ce8aff 100644
--- a/libmpathcmd/mpath_cmd.c
+++ b/libmpathcmd/mpath_cmd.c
@@ -64,7 +64,7 @@ static size_t write_all(int fd, const void *buf, size_t len)
}
if (!n)
return total;
-   buf = n + (char *)buf;
+   buf = n + (const char *)buf;
len -= n;
total += n;
}
diff --git a/libmultipath/checkers/rbd.c b/libmultipath/checkers/rbd.c
index 2c1800976e40..b1d99b4c81f6 100644
--- a/libmultipath/checkers/rbd.c
+++ b/libmultipath/checkers/rbd.c
@@ -288,7 +288,7 @@ void libcheck_free(struct checker * c)
 static int rbd_is_blacklisted(struct rbd_checker_context *ct, char *msg)
 {
char *addr_tok, *start, *save;
-   char *cmd[2];
+   const char *cmd[2];
char *blklist, *stat;
size_t blklist_len, stat_len;
int ret;
@@ -436,7 +436,7 @@ static int sysfs_write_rbd_remove(const char *buf, int 
buf_len)
 
 static int rbd_rm_blacklist(struct rbd_checker_context *ct)
 {
-   char *cmd[2];
+   const char *cmd[2];
char *stat, *cmd_str;
size_t stat_len;
int ret;
diff --git a/libmultipath/devmapper.c b/libmultipath/devmapper.c
index f61838cbe369..607aea8dc1fc 100644
--- a/libmultipath/devmapper.c
+++ b/libmultipath/devmapper.c
@@ -27,6 +27,7 @@
 #include 
 #include 
 
+#define FREE_CONST(p) do { free((void*)(unsigned long)p); p = NULL; } while(0)
 #define MAX_WAIT 5
 #define LOOPS_PER_SEC 5
 
@@ -1426,7 +1427,7 @@ void dm_reassign_deps(char *table, const char *dep, const 
char *newdep)
n += strlen(newdep);
p += strlen(dep);
strcat(n, p);
-   free(newtable);
+   FREE_CONST(newtable);
 }
 
 int dm_reassign_table(const char *name, char *old, char *new)
diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
index 98bddee52c8f..645224c1029c 100644
--- a/libmultipath/discovery.c
+++ b/libmultipath/discovery.c
@@ -121,7 +121,7 @@ path_discover (vector pathvec, struct config * conf,
if (!devname)
return PATHINFO_FAILED;
 
-   pp = find_path_by_dev(pathvec, (char *)devname);
+   pp = find_path_by_dev(pathvec, devname);
if (!pp) {
char devt[BLK_DEV_SIZE];
dev_t devnum = udev_device_get_devnum(udevice);
@@ -905,12 +905,12 @@ static int
 parse_vpd_pg83(const unsigned char *in, size_t in_len,
   char *out, size_t out_len)
 {
-   unsigned char *d;
-   unsigned char *vpd = NULL;
+   const unsigned char *d;
+   const unsigned char *vpd = NULL;
int len = -ENODATA, vpd_type, vpd_len, prio = -1, i, naa_prio;
 
-   d = (unsigned char *)in + 4;
-   while (d < (unsigned char *)in + in_len) {
+   d = in + 4;
+   while (d < in + in_len) {
/* Select 'association: LUN' */
if ((d[1] & 0x30) != 0) {
d += d[3] + 4;
@@ -1027,7 +1027,7 @@ parse_vpd_pg83(const unsigned char *in, size_t in_len,
out[len] = '\0';
}
} else if (vpd_type == 0x1) {
-   unsigned char *p;
+   const unsigned char *p;
int p_len;
 
out[0] = '1';
diff --git a/libmultipath/list.h b/libmultipath/list.h
index 2b1dcf396695..c9110ac9de7e 100644
--- a/libmultipath/list.h
+++ b/libmultipath/list.h
@@ -18,8 +18,8 @@
  * @member:the name of the member within the struct.
  *
  */
-#define container_of(ptr, type, member) ({ \
-   const typeof( ((type 

Re: [dm-devel] Device mapper for temporarily buffering writes on fast device before pushing to slower device

[Heinz Mauelshagen]

dm-writecache (see list archieve) is what you're looking for.


On 02/19/2018 09:47 PM, Drew Hastings wrote:
I found stochastic multi-queue and writeboost to be insufficient for 
this purpose. I'm wondering if anything exists that fits this 
description:


Device mapper creates a "cache" device on a fast device (SSD/NVME, 
etc)... and writes to the device *always* hit the fast device. Writes 
are later flushed to the slower device as fast as the slow device can 
handle them.


The problem with the caching solutions I have found with device mapper 
is that they require the block to be identified as "hot" first, even 
when the cache itself is not 100% utilized. Read performance is 
largely irrelevant.


Is there a device mapper implementation that works in this fashion; 
where 100% of writes happen to the fast device? I was thinking COW 
effectively does this, but the problem is it does not 
automatically/periodically flush writes, you have to do them all at once.


I had seen some conversations about trying to get the multiqueue (mq, 
not smq) policy to do this with zero values for thresholds, but it did 
not seem like any were successful in ensuring the first write would 
hit the fast device.


Thanks!


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dm-devel mailing list
dm-devel@redhat.com
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[dm-devel] Device mapper for temporarily buffering writes on fast device before pushing to slower device

[Drew Hastings]

I found stochastic multi-queue and writeboost to be insufficient for this
purpose. I'm wondering if anything exists that fits this description:

Device mapper creates a "cache" device on a fast device (SSD/NVME, etc)...
and writes to the device *always* hit the fast device. Writes are later
flushed to the slower device as fast as the slow device can handle them.

The problem with the caching solutions I have found with device mapper is
that they require the block to be identified as "hot" first, even when the
cache itself is not 100% utilized. Read performance is largely irrelevant.

Is there a device mapper implementation that works in this fashion; where
100% of writes happen to the fast device? I was thinking COW effectively
does this, but the problem is it does not automatically/periodically flush
writes, you have to do them all at once.

I had seen some conversations about trying to get the multiqueue (mq, not
smq) policy to do this with zero values for thresholds, but it did not seem
like any were successful in ensuring the first write would hit the fast
device.

Thanks!
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dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel