From 5248d8474e594d156bee1ed10339cc16e207a28b Mon Sep 17 00:00:00 2001 From: Olga Kornievskaia Date: Mon, 26 Jan 2026 14:15:39 -0500 Subject: [PATCH] pNFS: fix a missing wake up while waiting on NFS_LAYOUT_DRAIN It is possible to have a task get stuck on waiting on the NFS_LAYOUT_DRAIN in the following scenario 1. cpu a: waiter test NFS_LAYOUT_DRAIN (1) and plh_outstanding (1) 2. cpu b: atomic_dec_and_test() -> clear bit -> wake up 3. cpu c: sets NFS_LAYOUT_DRAIN again 4. cpu a: calls wait_on_bit() sleeps forever. To expand on this we have say 2 outstanding pnfs write IO that get ESTALE which causes both to call pnfs_destroy_layout() and set the NFS_LAYOUT_DRAIN bit but the 1st one doesn't call the pnfs_put_layout_hdr() yet (as that would prevent the 2nd ESTALE write from trying to call pnfs_destroy_layout()). If the 1st ESTALE write is the one that initially sets the NFS_LAYOUT_DRAIN so that new IO on this file initiates new LAYOUTGET. Another new write would find NFS_LAYOUT_DRAIN set and phl_outstanding>0 (step 1) and would wait_on_bit(). LAYOUTGET completes doing step 2. Now, the 2nd of ESTALE writes is calling pnfs_destory_layout() and set the NFS_LAYOUT_DRAIN bit (step 3). Finally, the waiting write wakes up to check the bit and goes back to sleep. The problem revolves around the fact that if NFS_LAYOUT_INVALID_STID was already set, it should not do the work of pnfs_mark_layout_stateid_invalid(), thus NFS_LAYOUT_DRAIN will not be set more than once for an invalid layout. Suggested-by: Trond Myklebust Fixes: 880265c77ac4 ("pNFS: Avoid a live lock condition in pnfs_update_layout()") Signed-off-by: Olga Kornievskaia Signed-off-by: Anna Schumaker --- fs/nfs/pnfs.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index cff225721d1ce..ff8483d3373a8 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -463,7 +463,8 @@ pnfs_mark_layout_stateid_invalid(struct pnfs_layout_hdr *lo, }; struct pnfs_layout_segment *lseg, *next; - set_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags); + if (test_and_set_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags)) + return !list_empty(&lo->plh_segs); clear_bit(NFS_INO_LAYOUTCOMMIT, &NFS_I(lo->plh_inode)->flags); list_for_each_entry_safe(lseg, next, &lo->plh_segs, pls_list) pnfs_clear_lseg_state(lseg, lseg_list); -- 2.47.3