During restart, an ipc shared region may have SHM_DEST, indicating
that it has been originally deleted (while still active). In this
case the task of deleting the region after restoring it is postponed
until the end of the restart; otherwise, it would be quite silly to
delete it at that time, because it will be ... gone :o
Changelog:
Apr 14 2009: Serge converts to generic deferqueue
Signed-off-by: Oren Laadan <[email protected]>
---
checkpoint/sys.c | 11 ++++++++++
include/linux/checkpoint.h | 1 +
ipc/ckpt_shm.c | 45 ++++++++++++++++++++++++++++++++++++++++---
3 files changed, 53 insertions(+), 4 deletions(-)
diff --git a/checkpoint/sys.c b/checkpoint/sys.c
index 63ee55e..3dfb7d9 100644
--- a/checkpoint/sys.c
+++ b/checkpoint/sys.c
@@ -16,6 +16,7 @@
#include <linux/uaccess.h>
#include <linux/capability.h>
#include <linux/checkpoint.h>
+#include <linux/deferqueue.h>
#include "checkpoint_mem.h"
@@ -171,8 +172,14 @@ static void cr_task_arr_free(struct cr_ctx *ctx)
static void cr_ctx_free(struct cr_ctx *ctx)
{
+ int ret;
+
BUG_ON(atomic_read(&ctx->refcount));
+ ret = deferqueue_run(ctx->deferqueue);
+ if (ret != 0)
+ cr_debug("deferred deferqueue had %d entries", ret);
+
if (ctx->file)
fput(ctx->file);
@@ -219,6 +226,10 @@ static struct cr_ctx *cr_ctx_alloc(int fd, unsigned long
flags)
goto err;
err = -ENOMEM;
+ ctx->deferqueue = deferqueue_create();
+ if (!ctx->deferqueue)
+ goto err;
+
ctx->hbuf = kmalloc(CR_HBUF_TOTAL, GFP_KERNEL);
if (!ctx->hbuf)
goto err;
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 7e8d4e0..82d2a40 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -42,6 +42,7 @@ struct cr_ctx {
atomic_t refcount;
struct cr_objhash *objhash; /* hash for shared objects */
+ struct deferqueue_head *deferqueue; /* list of deferred work */
struct list_head pgarr_list; /* page array to dump VMA contents */
struct list_head pgarr_pool; /* pool of empty page arrays chain */
diff --git a/ipc/ckpt_shm.c b/ipc/ckpt_shm.c
index ee9b77a..a944b67 100644
--- a/ipc/ckpt_shm.c
+++ b/ipc/ckpt_shm.c
@@ -18,6 +18,7 @@
#include <linux/syscalls.h>
#include <linux/nsproxy.h>
#include <linux/ipc_namespace.h>
+#include <linux/deferqueue.h>
#include <linux/msg.h> /* needed for util.h that uses 'struct msg_msg' */
#include "util.h"
@@ -145,6 +146,25 @@ int cr_write_ipc_shm(struct cr_ctx *ctx, struct
ipc_namespace *ipcns)
* ipc restart
*/
+struct cr_dq_ipcshm_del {
+ struct ipc_namespace *ipcns;
+ int id;
+};
+
+static int cr_ipc_shm_delete(void *data)
+{
+ struct cr_dq_ipcshm_del *dq = (struct cr_dq_ipcshm_del *) data;
+ mm_segment_t old_fs;
+ int ret;
+
+ old_fs = get_fs();
+ set_fs(get_ds());
+ ret = shmctl_down(dq->ipcns, dq->id, IPC_RMID, NULL, 0);
+ set_fs(old_fs);
+
+ return ret;
+}
+
int cr_ipc_shm_attach(struct file *file,
unsigned long vm_addr,
unsigned long vm_flags)
@@ -224,7 +244,25 @@ static int cr_do_read_ipc_shm(struct cr_ctx *ctx)
if (hh->flags & SHM_HUGETLB) /* FIXME: support SHM_HUGETLB */
goto out;
- /* FIXME: this will fail for deleted ipc shm segments */
+ /*
+ * SHM_DEST means that the shm is to be deleted after creation.
+ * However, deleting before it's actually attached is quite silly.
+ * Instead, we defer this task to until restart has succeeded.
+ */
+ if (hh->perms.mode & SHM_DEST) {
+ struct cr_dq_ipcshm_del dq;
+
+ /* to not confuse the rest of the code */
+ hh->perms.mode &= ~SHM_DEST;
+
+ dq.ipcns = current->nsproxy->ipc_ns;
+ dq.id = hh->perms.id;
+
+ ret = deferqueue_add(ctx->deferqueue, cr_ipc_shm_delete,
+ &dq, sizeof(dq));
+ if (ret < 0)
+ goto out;
+ }
shmflag = hh->flags | hh->perms.mode | IPC_CREAT | IPC_EXCL;
cr_debug("shm: do_shmget size %lld flag %#x id %d\n",
@@ -235,7 +273,6 @@ static int cr_do_read_ipc_shm(struct cr_ctx *ctx)
goto out;
down_write(&shm_ids->rw_mutex);
-
ret = -EIDRM;
perms = ipc_lock(shm_ids, hh->perms.id);
if (IS_ERR(perms)) { /* this should not happen .. but be safe */
@@ -261,9 +298,9 @@ static int cr_do_read_ipc_shm(struct cr_ctx *ctx)
/* deposit in objhash and read contents in */
ret = cr_obj_add_ref(ctx, file, hh->objref, CR_OBJ_FILE, 0);
if (ret < 0)
- goto file;
+ goto fput;
ret = cr_read_shmem_contents(ctx, file->f_dentry->d_inode);
- file:
+ fput:
fput(file);
out:
cr_hbuf_put(ctx, sizeof(*hh));
--
1.5.4.3
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