[PATCH 2/3] btrfs: optimize move uuid_mutex closer to the critical section

[Anand Jain]

Move uuid_mutex closer to the exclusion section.

Signed-off-by: Anand Jain 
---
 fs/btrfs/volumes.c | 17 -
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index a81574dba124..a7eb9b42cd92 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1187,13 +1187,10 @@ int btrfs_scan_one_device(const char *path, fmode_t 
flags, void *holder,
 */
bytenr = btrfs_sb_offset(0);
flags |= FMODE_EXCL;
-   mutex_lock(&uuid_mutex);
 
bdev = blkdev_get_by_path(path, flags, holder);
-   if (IS_ERR(bdev)) {
-   ret = PTR_ERR(bdev);
-   goto error;
-   }
+   if (IS_ERR(bdev))
+   return PTR_ERR(bdev);
 
if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super))
goto error_bdev_put;
@@ -1202,7 +1199,12 @@ int btrfs_scan_one_device(const char *path, fmode_t 
flags, void *holder,
transid = btrfs_super_generation(disk_super);
total_devices = btrfs_super_num_devices(disk_super);
 
+   mutex_lock(&uuid_mutex);
ret = device_list_add(path, disk_super, devid, fs_devices_ret);
+   if (ret >= 0 && fs_devices_ret)
+   (*fs_devices_ret)->total_devices = total_devices;
+   mutex_unlock(&uuid_mutex);
+
if (ret > 0) {
if (disk_super->label[0]) {
pr_info("BTRFS: device label %s ", disk_super->label);
@@ -1213,15 +1215,12 @@ int btrfs_scan_one_device(const char *path, fmode_t 
flags, void *holder,
pr_cont("devid %llu transid %llu %s\n", devid, transid, path);
ret = 0;
}
-   if (!ret && fs_devices_ret)
-   (*fs_devices_ret)->total_devices = total_devices;
 
btrfs_release_disk_super(page);
 
 error_bdev_put:
blkdev_put(bdev, flags);
-error:
-   mutex_unlock(&uuid_mutex);
+
return ret;
 }
 
-- 
2.7.0

--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH 2/3] btrfs: optimize move uuid_mutex closer to the critical section

[David Sterba]

On Fri, Dec 15, 2017 at 03:40:15PM +0800, Anand Jain wrote:
> Move uuid_mutex closer to the exclusion section.

Looks good, there's really something unrelated inside the critical
section so this could potentially speed up scanning devices.

Reviewed-by: David Sterba 
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html