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Olga Kornievskaia
b3a8b2bbc4
[ Upstream commit5248d8474e] 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 <trond.myklebust@hammerspace.com> Fixes:880265c77a("pNFS: Avoid a live lock condition in pnfs_update_layout()") Signed-off-by: Olga Kornievskaia <okorniev@redhat.com> Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com> Signed-off-by: Sasha Levin <sashal@kernel.org>