fuse: fix bdi naming conflict

Fuse allocates a separate bdi for each filesystem, and registers them
in sysfs with "MAJOR:MINOR" of sb->s_dev (st_dev).  This works fine for
anon devices normally used by fuse, but can conflict with an already
registered BDI for "fuseblk" filesystems, where sb->s_dev represents a
real block device.  In particularl this happens if a non-partitioned
device is being mounted.

Fix by registering with a different name for "fuseblk" filesystems.

Thanks to Ioan Ionita for the bug report.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Reported-by: Ioan Ionita <opslynx@gmail.com>
Tested-by: Ioan Ionita <opslynx@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 10 insertions, 1 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-bdi b/Documentation/ABI/testing/sysfs-class-bdi
index 5ac1e01bbd4..5f500977b42 100644
--- a/Documentation/ABI/testing/sysfs-class-bdi
+++ b/Documentation/ABI/testing/sysfs-class-bdi
@@ -14,6 +14,10 @@ MAJOR:MINOR
         non-block filesystems which provide their own BDI, such as NFS
         and FUSE.
 
+MAJOR:MINOR-fuseblk
+
+        Value of st_dev on fuseblk filesystems.
+
 default
 
         The default backing dev, used for non-block device backed
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index fb77e096213..43e99513334 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -488,7 +488,12 @@ static struct fuse_conn *new_conn(struct super_block *sb)
                 err = bdi_init(&fc->bdi);
                 if (err)
                         goto error_kfree;
-                err = bdi_register_dev(&fc->bdi, fc->dev);
+                if (sb->s_bdev) {
+                        err = bdi_register(&fc->bdi, NULL, "%u:%u-fuseblk",
+                                           MAJOR(fc->dev), MINOR(fc->dev));
+                } else {
+                        err = bdi_register_dev(&fc->bdi, fc->dev);
+                }
                 if (err)
                         goto error_bdi_destroy;
                 /*