This is a note to let you know that I've just added the patch titled
nfs: don't atempt blocking locks on nfs reexports
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nfs-don-t-atempt-blocking-locks-on-nfs-reexports.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 1f46d71fc8731c28978641a0a96a0bb62d194dd6
Author: J. Bruce Fields <bfields@xxxxxxxxxxxx>
Date: Fri Aug 20 17:02:04 2021 -0400
nfs: don't atempt blocking locks on nfs reexports
[ Upstream commit f657f8eef3ff870552c9fd2839e0061046f44618 ]
NFS implements blocking locks by blocking inside its lock method. In
the reexport case, this blocks the nfs server thread, which could lead
to deadlocks since an nfs server thread might be required to unlock the
conflicting lock. It also causes a crash, since the nfs server thread
assumes it can free the lock when its lm_notify lock callback is called.
Ideal would be to make the nfs lock method return without blocking in
this case, but for now it works just not to attempt blocking locks. The
difference is just that the original client will have to poll (as it
does in the v4.0 case) instead of getting a callback when the lock's
available.
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
Acked-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/nfs/export.c b/fs/nfs/export.c
index b347e3ce0cc8e..40beac65d1355 100644
--- a/fs/nfs/export.c
+++ b/fs/nfs/export.c
@@ -184,5 +184,5 @@ const struct export_operations nfs_export_ops = {
.fetch_iversion = nfs_fetch_iversion,
.flags = EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK|
EXPORT_OP_CLOSE_BEFORE_UNLINK|EXPORT_OP_REMOTE_FS|
- EXPORT_OP_NOATOMIC_ATTR,
+ EXPORT_OP_NOATOMIC_ATTR|EXPORT_OP_SYNC_LOCKS,
};
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 401f0f2743717..fd3bdf0bf0052 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -6878,6 +6878,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
struct nfsd4_blocked_lock *nbl = NULL;
struct file_lock *file_lock = NULL;
struct file_lock *conflock = NULL;
+ struct super_block *sb;
__be32 status = 0;
int lkflg;
int err;
@@ -6899,6 +6900,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
dprintk("NFSD: nfsd4_lock: permission denied!\n");
return status;
}
+ sb = cstate->current_fh.fh_dentry->d_sb;
if (lock->lk_is_new) {
if (nfsd4_has_session(cstate))
@@ -6947,7 +6949,8 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
fp = lock_stp->st_stid.sc_file;
switch (lock->lk_type) {
case NFS4_READW_LT:
- if (nfsd4_has_session(cstate))
+ if (nfsd4_has_session(cstate) &&
+ !(sb->s_export_op->flags & EXPORT_OP_SYNC_LOCKS))
fl_flags |= FL_SLEEP;
fallthrough;
case NFS4_READ_LT:
@@ -6959,7 +6962,8 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
fl_type = F_RDLCK;
break;
case NFS4_WRITEW_LT:
- if (nfsd4_has_session(cstate))
+ if (nfsd4_has_session(cstate) &&
+ !(sb->s_export_op->flags & EXPORT_OP_SYNC_LOCKS))
fl_flags |= FL_SLEEP;
fallthrough;
case NFS4_WRITE_LT:
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index fe848901fcc3a..3260fe7148462 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -221,6 +221,8 @@ struct export_operations {
#define EXPORT_OP_NOATOMIC_ATTR (0x10) /* Filesystem cannot supply
atomic attribute updates
*/
+#define EXPORT_OP_SYNC_LOCKS (0x20) /* Filesystem can't do
+ asychronous blocking locks */
unsigned long flags;
};
