nfsd: use fsnotify group lock helpers

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@gmail.com
Suggested-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220321112310.vpr7oxro2xkz5llh@quack3.lan/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 74ddb82..489c9c1 100644 (file)
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -119,14 +119,14 @@ 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;
@@ -134,8 +134,9 @@ 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);
@@ -679,7 +680,7 @@ 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));