[PATCH 4.19 333/361] btrfs: iterate all devices during trim, instead of fs_devices::alloc_list

Greg Kroah-Hartman
2018-11-11T23:48:44Z

From: Jeff Mahoney <jeffm@suse.com>

commit d4e329de5e5e21594df2e0dd59da9acee71f133b upstream.

btrfs_trim_fs iterates over the fs_devices->alloc_list while holding the
device_list_mutex. The problem is that ->alloc_list is protected by the
chunk mutex. We don't want to hold the chunk mutex over the trim of the
entire file system. Fortunately, the ->dev_list list is protected by
the dev_list mutex and while it will give us all devices, including
read-only devices, we already just skip the read-only devices. Then we
can continue to take and release the chunk mutex while scanning each
device.

Fixes: 499f377f49f ("btrfs: iterate over unused chunk space in FITRIM")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/extent-tree.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10920,8 +10920,8 @@ int btrfs_trim_fs(struct btrfs_fs_info *
"failed to trim %llu block group(s), last error %d",
bg_failed, bg_ret);
mutex_lock(&fs_info->fs_devices->device_list_mutex);
- devices = &fs_info->fs_devices->alloc_list;
- list_for_each_entry(device, devices, dev_alloc_list) {
+ devices = &fs_info->fs_devices->devices;
+ list_for_each_entry(device, devices, dev_list) {
ret = btrfs_trim_free_extents(device, range->minlen,
&group_trimmed);
if (ret) {