The commit is pushed to "branch-rh7-3.10.0-693.21.1.vz7.50.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-693.21.1.vz7.50.4
------>
commit e6b0bf08eaa2b09c9d560c8db76641087c596f88
Author: Kirill Tkhai <ktk...@virtuozzo.com>
Date: Mon Jun 4 23:24:14 2018 +0300
fuse kio: Introduce pcs_cs::use_count instead of ::is_probing
This patch generalizes is_probing and this allows to prohibit
cs isolation after unlocking of cs::lock, not only in bl_timer_work().
Signed-off-by: Kirill Tkhai <ktk...@virtuozzo.com>
=====================
Patchset description:
Fix deadlock during change of CS address
This is not a complete patchset, but I meet the situation
when it's necessary to change original logic in small way,
so this is a request for comments.
[1-5/7] are mostly preparations and fixes, so my question
is about [6-7/7].
1) Patch 6 changes order of actions: pcs_map_notify_addr_change()
is called after assigning of rpc addr. Can we do that? As I
understand this results in new maps are created with new address,
while in pcs_map_notify_addr_change() we invalidate old ones.
So, for me it seems there is no a problem.
This is needed for possibility to unlock cs->lock in
pcs_map_notify_addr_change().
Theoretically, two pcs_cs_find_create() may happen in parallel,
so we want they assign addr in the order they happen. Otherwise,
the first one with the old addr_serno may overwrite the addr.
2) Patch 7 uses the preparations from previous patches and
makes pcs_map_notify_addr_change() to unlock cs->lock for a while.
New elements are added to head of cs->map_list, so we skip
them on iterations. But it seems, they must be correct because
we already updated rpc addr in pcs_cs_find_create(). Is there
a reason we can't do this?
Kirill Tkhai (7):
fuse kio: Introduce pcs_cs_list_of_cs_link()
fuse kio: Fix potential use after free
fuse kio: Fix possible use after free in cslist_destroy()
fuse kio: Introduce pcs_cs::use_count instead of ::is_probing
fuse kio: Wait till cs is unused in pcs_csset_fini()
fuse kio: Change order around pcs_map_notify_addr_change()
fuse kio: Fix fix deadlock during change CS address
---
fs/fuse/kio/pcs/pcs_cs.c | 10 +++++-----
fs/fuse/kio/pcs/pcs_cs.h | 2 +-
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/fs/fuse/kio/pcs/pcs_cs.c b/fs/fuse/kio/pcs/pcs_cs.c
index 0b6c4f248251..5cf7d73de67b 100644
--- a/fs/fuse/kio/pcs/pcs_cs.c
+++ b/fs/fuse/kio/pcs/pcs_cs.c
@@ -82,7 +82,7 @@ struct pcs_cs *pcs_cs_alloc(struct pcs_cs_set *css,
cs->nflows = 0;
cs->state = 0;
- cs->is_probing = 0;
+ cs->use_count = 0;
cs->is_dead = 0;
INIT_LIST_HEAD(&cs->bl_link);
@@ -957,7 +957,7 @@ static void cs_probe_done(struct pcs_msg *msg)
TRACE("probe error %d", msg->error.value);
cs_blacklist(cs, msg->error.value, "probe");
}
- cs->is_probing = 0;
+ cs->use_count--;
}
spin_unlock(&cs->lock);
pcs_free_msg(msg);
@@ -1015,7 +1015,7 @@ static void bl_timer_work(struct work_struct *w)
spin_lock(&cs->lock);
BUG_ON(cs->is_dead);
list_move(&cs->bl_link, &to_blacklist);
- if (cs->is_probing) {
+ if (cs->use_count) {
spin_unlock(&cs->lock);
continue;
}
@@ -1025,14 +1025,14 @@ static void bl_timer_work(struct work_struct *w)
pcs_cs_destroy(cs);
continue;
}
- cs->is_probing = 1;
+ cs->use_count++;
spin_unlock(&cs->lock);
msg = cs_prep_probe(cs);
if (msg)
pcs_rpc_call(cs->rpc, msg);
spin_lock(&cs->lock);
if (!msg)
- cs->is_probing = 0;
+ cs->use_count--;
spin_unlock(&cs->lock);
}
spin_lock(&css->lock);
diff --git a/fs/fuse/kio/pcs/pcs_cs.h b/fs/fuse/kio/pcs/pcs_cs.h
index eb81ac51f3ae..1fb40936d046 100644
--- a/fs/fuse/kio/pcs/pcs_cs.h
+++ b/fs/fuse/kio/pcs/pcs_cs.h
@@ -76,8 +76,8 @@ struct pcs_cs {
unsigned long state;
int blacklist_reason;
+ unsigned int use_count; /* Protects cs against isolation */
struct list_head bl_link;
- unsigned is_probing:1;
unsigned is_dead:1;
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