We found a few different systems hung up in writeback waiting on the same
page lock, and one task waiting on the NFS_LAYOUT_DRAIN bit in
pnfs_update_layout(), however the pnfs_layout_hdr's plh_outstanding count
was zero.
It seems most likely that this is another race between the waiter and waker
similar to commit ed0172af5d6f ("SUNRPC: Fix a race to wake a sync task").
Fix it up by applying the advised barrier.
Fixes: 880265c77ac4 ("pNFS: Avoid a live lock condition in pnfs_update_layout()")
Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
---
fs/nfs/pnfs.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 5f582713bf05..4291ac4cfdf1 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -2042,8 +2042,10 @@ static void nfs_layoutget_begin(struct pnfs_layout_hdr *lo)
static void nfs_layoutget_end(struct pnfs_layout_hdr *lo)
{
if (atomic_dec_and_test(&lo->plh_outstanding) &&
- test_and_clear_bit(NFS_LAYOUT_DRAIN, &lo->plh_flags))
+ test_and_clear_bit(NFS_LAYOUT_DRAIN, &lo->plh_flags)) {
+ smp_mb__after_atomic();
wake_up_bit(&lo->plh_flags, NFS_LAYOUT_DRAIN);
+ }
}
static bool pnfs_is_first_layoutget(struct pnfs_layout_hdr *lo)
--
2.47.0
