NLM/NFSD: Fix lock notifications for async-capable filesystems

Instead of checking just the exportfs flag, use the new
locks_can_async_lock() helper which allows NLM and NFSD to once again
support lock notifications for all filesystems which use posix_lock_file().

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Link: https://lore.kernel.org/r/865c40da44af67939e8eb560d17a26c9c50f23e0.1726083391.git.bcodding@redhat.com
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/lockd/svclock.c

@@ -30,7 +30,6 @@
 #include <linux/sunrpc/svc_xprt.h>
 #include <linux/lockd/nlm.h>
 #include <linux/lockd/lockd.h>
-#include <linux/exportfs.h>
 
 #define NLMDBG_FACILITY		NLMDBG_SVCLOCK
 
@@ -481,7 +480,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 	    struct nlm_host *host, struct nlm_lock *lock, int wait,
 	    struct nlm_cookie *cookie, int reclaim)
 {
-	struct inode		*inode = nlmsvc_file_inode(file);
+	struct inode		*inode __maybe_unused = nlmsvc_file_inode(file);
 	struct nlm_block	*block = NULL;
 	int			error;
 	int			mode;
@@ -496,7 +495,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 				(long long)lock->fl.fl_end,
 				wait);
 
-	if (!exportfs_lock_op_is_async(inode->i_sb->s_export_op)) {
+	if (!locks_can_async_lock(nlmsvc_file_file(file)->f_op)) {
 		async_block = wait;
 		wait = 0;
 	}
@@ -550,7 +549,7 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
 	 * requests on the underlaying ->lock() implementation but
 	 * only one nlm_block to being granted by lm_grant().
 	 */
-	if (exportfs_lock_op_is_async(inode->i_sb->s_export_op) &&
+	if (locks_can_async_lock(nlmsvc_file_file(file)->f_op) &&
 	    !list_empty(&block->b_list)) {
 		spin_unlock(&nlm_blocked_lock);
 		ret = nlm_lck_blocked;

fs/nfsd/nfs4state.c

@@ -7953,9 +7953,6 @@ 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) ||
-			    exportfs_lock_op_is_async(sb->s_export_op))
-				flags |= FL_SLEEP;
 			fallthrough;
 		case NFS4_READ_LT:
 			spin_lock(&fp->fi_lock);
@@ -7966,9 +7963,6 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 			type = F_RDLCK;
 			break;
 		case NFS4_WRITEW_LT:
-			if (nfsd4_has_session(cstate) ||
-			    exportfs_lock_op_is_async(sb->s_export_op))
-				flags |= FL_SLEEP;
 			fallthrough;
 		case NFS4_WRITE_LT:
 			spin_lock(&fp->fi_lock);
@@ -7988,15 +7982,10 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 		goto out;
 	}
 
-	/*
-	 * Most filesystems with their own ->lock operations will block
-	 * the nfsd thread waiting to acquire the lock.  That leads to
-	 * deadlocks (we don't want every nfsd thread tied up waiting
-	 * for file locks), so don't attempt blocking lock notifications
-	 * on those filesystems:
-	 */
-	if (!exportfs_lock_op_is_async(sb->s_export_op))
-		flags &= ~FL_SLEEP;
+	if (lock->lk_type & (NFS4_READW_LT | NFS4_WRITEW_LT) &&
+		nfsd4_has_session(cstate) &&
+		locks_can_async_lock(nf->nf_file->f_op))
+			flags |= FL_SLEEP;
 
 	nbl = find_or_allocate_block(lock_sop, &fp->fi_fhandle, nn);
 	if (!nbl) {