5.15-stable review patch. If anyone has any objections, please let me know.
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From: Li Lingfeng lilingfeng3@huawei.com
[ Upstream commit a1d14d931bf700c1025db8c46d6731aa5cf440f9 ]
A deadlock warning occurred when invoking nfs4_put_stid following a failed dl_recall queue operation: T1 T2 nfs4_laundromat nfs4_get_client_reaplist nfs4_anylock_blockers __break_lease spin_lock // ctx->flc_lock spin_lock // clp->cl_lock nfs4_lockowner_has_blockers locks_owner_has_blockers spin_lock // flctx->flc_lock nfsd_break_deleg_cb nfsd_break_one_deleg nfs4_put_stid refcount_dec_and_lock spin_lock // clp->cl_lock
When a file is opened, an nfs4_delegation is allocated with sc_count initialized to 1, and the file_lease holds a reference to the delegation. The file_lease is then associated with the file through kernel_setlease.
The disassociation is performed in nfsd4_delegreturn via the following call chain: nfsd4_delegreturn --> destroy_delegation --> destroy_unhashed_deleg --> nfs4_unlock_deleg_lease --> kernel_setlease --> generic_delete_lease The corresponding sc_count reference will be released after this disassociation.
Since nfsd_break_one_deleg executes while holding the flc_lock, the disassociation process becomes blocked when attempting to acquire flc_lock in generic_delete_lease. This means: 1) sc_count in nfsd_break_one_deleg will not be decremented to 0; 2) The nfs4_put_stid called by nfsd_break_one_deleg will not attempt to acquire cl_lock; 3) Consequently, no deadlock condition is created.
Given that sc_count in nfsd_break_one_deleg remains non-zero, we can safely perform refcount_dec on sc_count directly. This approach effectively avoids triggering deadlock warnings.
Fixes: 230ca758453c ("nfsd: put dl_stid if fail to queue dl_recall") Signed-off-by: Li Lingfeng lilingfeng3@huawei.com Reviewed-by: Jeff Layton jlayton@kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nfsd/nfs4state.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 5e576b1f46c79..1d09fb4ff5a5e 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -4944,7 +4944,7 @@ static void nfsd_break_one_deleg(struct nfs4_delegation *dp) queued = nfsd4_run_cb(&dp->dl_recall); WARN_ON_ONCE(!queued); if (!queued) - nfs4_put_stid(&dp->dl_stid); + refcount_dec(&dp->dl_stid.sc_count); }
/* Called from break_lease() with flc_lock held. */