eventfs: Use GFP_NOFS for allocation when eventfs_mutex is held

If memory reclaim happens, it can reclaim file system pages. The file
system pages from eventfs may take the eventfs_mutex on reclaim. This
means that allocation while holding the eventfs_mutex must not call into
filesystem reclaim. A lockdep splat uncovered this.

Link: https://lkml.kernel.org/r/20231121231112.373501894@goodmis.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 28e12c09f5aa0 ("eventfs: Save ownership and mode")
Fixes: 5790b1fb3d672 ("eventfs: Remove eventfs_file and just use eventfs_inode")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 3eb6c622a74d200e3fce864e9cc87602b2c82faa..56d192f0ead89293b47889fda0f03a7fed6ec5c3 100644 (file)
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -95,7 +95,7 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
        if (!(dentry->d_inode->i_mode & S_IFDIR)) {
                if (!ei->entry_attrs) {
                        ei->entry_attrs = kzalloc(sizeof(*ei->entry_attrs) * ei->nr_entries,
-                                                 GFP_KERNEL);
+                                                 GFP_NOFS);
                        if (!ei->entry_attrs) {
                                ret = -ENOMEM;
                                goto out;
@@ -627,7 +627,7 @@ static int add_dentries(struct dentry ***dentries, struct dentry *d, int cnt)
 {
        struct dentry **tmp;
 
-       tmp = krealloc(*dentries, sizeof(d) * (cnt + 2), GFP_KERNEL);
+       tmp = krealloc(*dentries, sizeof(d) * (cnt + 2), GFP_NOFS);
        if (!tmp)
                return -1;
        tmp[cnt] = d;