Recently merged shared-sb capability causes kernel to crash when
we try to do mounts and umounts simultaneously on the same machine.
The patch fixes umount codepath by doing kill_anon_super at first
(it calls generic_shutdown_super that tries to take sb_lock and
removes a superblock from fs_supers list) and then processing
cifs_umount (that frees cifs related fields).
In this case when we call sget and it calls cifs_match_super under
sb_lock for every entry from fs_supers list, we can be sure that
all cifs related fields are not freed by simultaneous umount.
Signed-off-by: Pavel Shilovsky <piastryyy@xxxxxxxxx>
---
fs/cifs/cifsfs.c | 19 ++++++++++++++++---
1 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 989442d..3537e7d 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -180,16 +180,30 @@ out_mount_failed:
static void
cifs_put_super(struct super_block *sb)
{
+ struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
+ if (cifs_sb == NULL) {
+ cFYI(1, "Empty cifs superblock info passed to put_super");
+ return;
+ }
+
+ bdi_destroy(&cifs_sb->bdi);
+}
+
+static void
+cifs_kill_super(struct super_block *sb)
+{
int rc = 0;
struct cifs_sb_info *cifs_sb;
cFYI(1, "In cifs_put_super");
cifs_sb = CIFS_SB(sb);
if (cifs_sb == NULL) {
- cFYI(1, "Empty cifs superblock info passed to unmount");
+ cFYI(1, "Empty cifs superblock info passed to kill_super");
return;
}
+ kill_anon_super(sb);
+
rc = cifs_umount(sb, cifs_sb);
if (rc)
cERROR(1, "cifs_umount failed with return code %d", rc);
@@ -199,7 +213,6 @@ cifs_put_super(struct super_block *sb)
}
unload_nls(cifs_sb->local_nls);
- bdi_destroy(&cifs_sb->bdi);
kfree(cifs_sb);
}
@@ -807,7 +820,7 @@ struct file_system_type cifs_fs_type = {
.owner = THIS_MODULE,
.name = "cifs",
.mount = cifs_do_mount,
- .kill_sb = kill_anon_super,
+ .kill_sb = cifs_kill_super,
/* .fs_flags */
};
const struct inode_operations cifs_dir_inode_ops = {
--
1.7.1
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