The patch titled
vfs: don't hold s_umount over close_bdev_exclusive() call
has been added to the -mm tree. Its filename is
vfs-dont-hold-s_umount-over-close_bdev_exclusive-call.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: vfs: don't hold s_umount over close_bdev_exclusive() call
From: Tejun Heo <tj@xxxxxxxxxx>
Fix an obscure AB-BA deadlock in get_sb_bdev().
When a superblock is mounted more than once get_sb_bdev() calls
close_bdev_exclusive() to drop the extra bdev reference while holding
s_umount. However, sb->s_umount nests inside bd_mutex during
__invalidate_device() and close_bdev_exclusive() acquires bd_mutex during
blkdev_put(); thus creating an AB-BA deadlock.
This condition doesn't trigger frequently. For this condition to be
visible to lockdep, the filesystem must occupy the whole device (as
__invalidate_device() only grabs bd_mutex for the whole device), the FS
must be mounted more than once and partition rescan should be issued while
the FS is still mounted.
Fix it by dropping s_umount over close_bdev_exclusive().
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Reported-by: Ciprian Docan <docan@xxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Acked-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/super.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff -puN fs/super.c~vfs-dont-hold-s_umount-over-close_bdev_exclusive-call fs/super.c
--- a/fs/super.c~vfs-dont-hold-s_umount-over-close_bdev_exclusive-call
+++ a/fs/super.c
@@ -767,7 +767,16 @@ int get_sb_bdev(struct file_system_type
goto error_bdev;
}
+ /*
+ * s_umount nests inside bd_mutex during
+ * __invalidate_device(). close_bdev_exclusive()
+ * acquires bd_mutex and can't be called under
+ * s_umount. Drop s_umount temporarily. This is safe
+ * as we're holding an active reference.
+ */
+ up_write(&s->s_umount);
close_bdev_exclusive(bdev, mode);
+ down_write(&s->s_umount);
} else {
char b[BDEVNAME_SIZE];
_
Patches currently in -mm which might be from tj@xxxxxxxxxx are
origin.patch
linux-next.patch
vfs-dont-hold-s_umount-over-close_bdev_exclusive-call.patch
fix-stop_machine-reimplement-using-cpu_stop.patch
percpu-online-cpu-before-memory-failed-in-pcpu_alloc_pages.patch
percpu-fix-list_head-init-bug-in-__percpu_counter_init.patch
idr-fix-backtrack-logic-in-idr_remove_all.patch
idr-fix-backtrack-logic-in-idr_remove_all-update.patch
numa-add-generic-percpu-var-numa_node_id-implementation.patch
numa-add-generic-percpu-var-numa_node_id-implementation-fix1.patch
numa-add-generic-percpu-var-numa_node_id-implementation-fix2.patch
numa-x86_64-use-generic-percpu-var-numa_node_id-implementation.patch
numa-x86_64-use-generic-percpu-var-numa_node_id-implementation-fix1.patch
numa-x86_64-use-generic-percpu-var-numa_node_id-implementation-fix2.patch
numa-ia64-use-generic-percpu-var-numa_node_id-implementation.patch
numa-introduce-numa_mem_id-effective-local-memory-node-id.patch
numa-introduce-numa_mem_id-effective-local-memory-node-id-fix2.patch
numa-introduce-numa_mem_id-effective-local-memory-node-id-fix3.patch
numa-ia64-support-numa_mem_id-for-memoryless-nodes.patch
numa-slab-use-numa_mem_id-for-slab-local-memory-node.patch
numa-in-kernel-profiling-use-cpu_to_mem-for-per-cpu-allocations.patch
numa-update-documentation-vm-numa-add-memoryless-node-info.patch
numa-update-documentation-vm-numa-add-memoryless-node-info-fix1.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
