Patch "nfsd: use fsnotify group lock helpers" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    nfsd: use fsnotify group lock helpers

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nfsd-use-fsnotify-group-lock-helpers.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 9752105c4d608d3bff236294201615e5eb2b9c07
Author: Amir Goldstein <amir73il@xxxxxxxxx>
Date:   Fri Apr 22 15:03:20 2022 +0300

    nfsd: use fsnotify group lock helpers
    
    [ Upstream commit b8962a9d8cc2d8c93362e2f684091c79f702f6f3 ]
    
    Before commit 9542e6a643fc6 ("nfsd: Containerise filecache laundrette")
    nfsd would close open files in direct reclaim context and that could
    cause a deadlock when fsnotify mark allocation went into direct reclaim
    and nfsd shrinker tried to free existing fsnotify marks.
    
    To avoid issues like this in future code, set the FSNOTIFY_GROUP_NOFS
    flag on nfsd fsnotify group to prevent going into direct reclaim from
    fsnotify_add_inode_mark().
    
    Link: https://lore.kernel.org/r/20220422120327.3459282-10-amir73il@xxxxxxxxx
    Suggested-by: Jan Kara <jack@xxxxxxx>
    Link: https://lore.kernel.org/r/20220321112310.vpr7oxro2xkz5llh@xxxxxxxxxx/
    Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
    Signed-off-by: Jan Kara <jack@xxxxxxx>
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 97ca256a76323..b1afe6db589f2 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -118,14 +118,14 @@ nfsd_file_mark_find_or_create(struct nfsd_file *nf)
 	struct inode *inode = nf->nf_inode;
 
 	do {
-		mutex_lock(&nfsd_file_fsnotify_group->mark_mutex);
+		fsnotify_group_lock(nfsd_file_fsnotify_group);
 		mark = fsnotify_find_mark(&inode->i_fsnotify_marks,
-				nfsd_file_fsnotify_group);
+					  nfsd_file_fsnotify_group);
 		if (mark) {
 			nfm = nfsd_file_mark_get(container_of(mark,
 						 struct nfsd_file_mark,
 						 nfm_mark));
-			mutex_unlock(&nfsd_file_fsnotify_group->mark_mutex);
+			fsnotify_group_unlock(nfsd_file_fsnotify_group);
 			if (nfm) {
 				fsnotify_put_mark(mark);
 				break;
@@ -133,8 +133,9 @@ nfsd_file_mark_find_or_create(struct nfsd_file *nf)
 			/* Avoid soft lockup race with nfsd_file_mark_put() */
 			fsnotify_destroy_mark(mark, nfsd_file_fsnotify_group);
 			fsnotify_put_mark(mark);
-		} else
-			mutex_unlock(&nfsd_file_fsnotify_group->mark_mutex);
+		} else {
+			fsnotify_group_unlock(nfsd_file_fsnotify_group);
+		}
 
 		/* allocate a new nfm */
 		new = kmem_cache_alloc(nfsd_file_mark_slab, GFP_KERNEL);
@@ -672,7 +673,7 @@ nfsd_file_cache_init(void)
 	}
 
 	nfsd_file_fsnotify_group = fsnotify_alloc_group(&nfsd_file_fsnotify_ops,
-							0);
+							FSNOTIFY_GROUP_NOFS);
 	if (IS_ERR(nfsd_file_fsnotify_group)) {
 		pr_err("nfsd: unable to create fsnotify group: %ld\n",
 			PTR_ERR(nfsd_file_fsnotify_group));