shmem: allow reporting fanotify events with file handles on tmpfs

amir73il · jankara · commit 59cda49ecf6c · 2021-04-19T16:03:48.000+02:00
Since kernel v5.1, fanotify_init(2) supports the flag FAN_REPORT_FID for identifying objects using file handle and fsid in events. fanotify_mark(2) fails with -ENODEV when trying to set a mark on filesystems that report null f_fsid in stasfs(2). Use the digest of uuid as f_fsid for tmpfs to uniquely identify tmpfs objects as best as possible and allow setting an fanotify mark that reports events with file handles on tmpfs. Link: https://lore.kernel.org/r/20210322173944.449469-3-amir73il@gmail.com Acked-by: Hugh Dickins <hughd@google.com> Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/mm/shmem.c b/mm/shmem.c
@@ -2846,6 +2846,9 @@ static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
 		buf->f_ffree = sbinfo->free_inodes;
 	}
 	/* else leave those fields 0 like simple_statfs */
+
+	buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);
+
 	return 0;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -2846,6 +2846,9 @@ static int shmem_statfs(struct dentry dentry, struct kstatfs buf)`
`2846`	`2846`	`buf->f_ffree = sbinfo->free_inodes;`
`2847`	`2847`	`}`
`2848`	`2848`	`/* else leave those fields 0 like simple_statfs */`
	`2849`	`+`
	`2850`	`+ buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);`
	`2851`	`+`
`2849`	`2852`	`return 0;`
`2850`	`2853`	`}`
`2851`	`2854`