btrfs: tag error branches as unlikely during super block writes

Mark all the unexpected error checks as unlikely, to make it more clear
they are unexpected and to allow the compiler to potentially generate
better code.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 177b211dfa05242012710781acd0ddd84d52323b..89f5423f0366c45649e8619c8ad62d8cb9c18105 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2591,7 +2591,7 @@ static int btrfs_validate_write_super(struct btrfs_fs_info *fs_info,
        int ret;
 
        ret = btrfs_validate_super(fs_info, sb, -1);
-       if (ret < 0)
+       if (unlikely(ret < 0))
                goto out;
        if (unlikely(!btrfs_supported_super_csum(btrfs_super_csum_type(sb)))) {
                ret = -EUCLEAN;
@@ -2608,7 +2608,7 @@ static int btrfs_validate_write_super(struct btrfs_fs_info *fs_info,
                goto out;
        }
 out:
-       if (ret < 0)
+       if (unlikely(ret < 0))
                btrfs_err(fs_info,
                "super block corruption detected before writing it to disk");
        return ret;
@@ -3869,7 +3869,7 @@ static int wait_dev_supers(struct btrfs_device *device, int max_mirrors)
                ret = btrfs_sb_log_location(device, i, READ, &bytenr);
                if (ret == -ENOENT) {
                        break;
-               } else if (ret < 0) {
+               } else if (unlikely(ret < 0)) {
                        errors++;
                        if (i == 0)
                                primary_failed = true;
@@ -3891,9 +3891,8 @@ static int wait_dev_supers(struct btrfs_device *device, int max_mirrors)
        }
 
        errors += atomic_read(&device->sb_write_errors);
-       if (errors >= BTRFS_SUPER_PRIMARY_WRITE_ERROR)
-               primary_failed = true;
-       if (primary_failed) {
+
+       if (unlikely(primary_failed || errors >= BTRFS_SUPER_PRIMARY_WRITE_ERROR)) {
                btrfs_err(device->fs_info, "error writing primary super block to device %llu",
                          device->devid);
                return -1;
@@ -3944,7 +3943,7 @@ static bool wait_dev_flush(struct btrfs_device *device)
 
        wait_for_completion_io(&device->flush_wait);
 
-       if (bio->bi_status) {
+       if (unlikely(bio->bi_status)) {
                set_bit(BTRFS_DEV_STATE_FLUSH_FAILED, &device->dev_state);
                btrfs_dev_stat_inc_and_print(device, BTRFS_DEV_STAT_FLUSH_ERRS);
                return true;
@@ -3982,7 +3981,7 @@ static int barrier_all_devices(struct btrfs_fs_info *info)
        list_for_each_entry(dev, head, dev_list) {
                if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state))
                        continue;
-               if (!dev->bdev) {
+               if (unlikely(!dev->bdev)) {
                        errors_wait++;
                        continue;
                }
@@ -3990,7 +3989,7 @@ static int barrier_all_devices(struct btrfs_fs_info *info)
                    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
                        continue;
 
-               if (wait_dev_flush(dev))
+               if (unlikely(wait_dev_flush(dev)))
                        errors_wait++;
        }
 
@@ -4068,7 +4067,7 @@ int write_all_supers(struct btrfs_trans_handle *trans, int max_mirrors)
 
        if (do_barriers) {
                ret = barrier_all_devices(fs_info);
-               if (ret) {
+               if (unlikely(ret)) {
                        mutex_unlock(
                                &fs_info->fs_devices->device_list_mutex);
                        btrfs_abort_transaction(trans, ret);
@@ -4078,7 +4077,7 @@ int write_all_supers(struct btrfs_trans_handle *trans, int max_mirrors)
        }
 
        list_for_each_entry(dev, head, dev_list) {
-               if (!dev->bdev) {
+               if (unlikely(!dev->bdev)) {
                        total_errors++;
                        continue;
                }
@@ -4113,7 +4112,7 @@ int write_all_supers(struct btrfs_trans_handle *trans, int max_mirrors)
                }
 
                ret = write_dev_supers(dev, sb, max_mirrors);
-               if (ret)
+               if (unlikely(ret))
                        total_errors++;
        }
        if (unlikely(total_errors > max_errors)) {
@@ -4129,14 +4128,14 @@ int write_all_supers(struct btrfs_trans_handle *trans, int max_mirrors)
 
        total_errors = 0;
        list_for_each_entry(dev, head, dev_list) {
-               if (!dev->bdev)
+               if (unlikely(!dev->bdev))
                        continue;
                if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
                    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
                        continue;
 
                ret = wait_dev_supers(dev, max_mirrors);
-               if (ret)
+               if (unlikely(ret))
                        total_errors++;
        }
        mutex_unlock(&fs_info->fs_devices->device_list_mutex);