btrfs: iterate all devices during trim, instead of fs_devices::alloc_list

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>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index da3257585e29e43a7d17991d05cc0981cfb67eb8..41fb24da7afa1752278c068252934f9efa0740bb 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -10903,8 +10903,8 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
                        "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) {