shm_ids->rw_mutex protects namespace-wide shm info, but not the
attributes or contents of individual shm regions, so release it as
soon as possible in the restart path.
The SHM_HUGETLB-specific restore code (unfortunately) needs to take
mmap_sem, which cannot be taken while holding shm_ids->rw_mutex (see
sys_shmdt -> do_munmap -> shm_close), so this is a prerequisite for
restoring hugetlb shm regions.
Signed-off-by: Nathan Lynch <ntl@xxxxxxxxx>
---
ipc/checkpoint_shm.c | 8 ++++----
1 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/ipc/checkpoint_shm.c b/ipc/checkpoint_shm.c
index a929e33..69ba35a 100644
--- a/ipc/checkpoint_shm.c
+++ b/ipc/checkpoint_shm.c
@@ -284,19 +284,19 @@ int restore_ipc_shm(struct ckpt_ctx *ctx, struct ipc_namespace *ns)
/* this is safe because no unauthorized access is possible */
ipc_unlock(ipc);
+ up_write(&shm_ids->rw_mutex);
ret = load_ipc_shm_hdr(ctx, h, shp);
if (ret < 0)
- goto mutex;
+ goto fput;
/* deposit in objhash and read contents in */
ret = ckpt_obj_insert(ctx, file, h->objref, CKPT_OBJ_FILE);
if (ret < 0)
- goto mutex;
+ goto fput;
ret = restore_memory_contents(ctx, file->f_dentry->d_inode);
- mutex:
+fput:
fput(file);
- up_write(&shm_ids->rw_mutex);
/* discard this shmid if error and deferqueue wasn't set */
if (ret < 0 && !(h->perms.mode & SHM_DEST)) {
--
1.7.2.2
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