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vfs: Remove unnecessary flushing of block devices 

It is not necessary to write block devices twice. The reason why we first did
flush and then proper sync is that
  for_each_bdev() {
    write_bdev()
    wait_for_completion()
  }
is much slower than
  for_each_bdev()
    write_bdev()
  for_each_bdev()
    wait_for_completion()
when there is bigger amount of data. But as is seen in the above, there's no real
need to scan pages and submit them twice. We just need to separate the submission
and waiting part. This patch does that.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Jan Kara 2012-07-03 16:45:33 +02:00 committed by Al Viro
parent a8c7176b6d
commit d0e91b13eb
1 changed files with 8 additions and 8 deletions
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16
fs/sync.c
View File

@ -85,14 +85,14 @@ static void sync_fs_one_sb(struct super_block *sb, void *arg)
sb->s_op->sync_fs(sb, *(int *)arg);
}
static void flush_one_bdev(struct block_device *bdev, void *arg)
static void fdatawrite_one_bdev(struct block_device *bdev, void *arg)
{
__sync_blockdev(bdev, 0);
filemap_fdatawrite(bdev->bd_inode->i_mapping);
}
static void sync_one_bdev(struct block_device *bdev, void *arg)
static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
{
sync_blockdev(bdev);
filemap_fdatawait(bdev->bd_inode->i_mapping);
}
/*
@ -106,10 +106,10 @@ SYSCALL_DEFINE0(sync)
wakeup_flusher_threads(0, WB_REASON_SYNC);
iterate_supers(writeback_inodes_one_sb, NULL);
iterate_supers(sync_fs_one_sb, &nowait);
iterate_bdevs(flush_one_bdev, NULL);
iterate_supers(sync_inodes_one_sb, NULL);
iterate_supers(sync_fs_one_sb, &wait);
iterate_bdevs(sync_one_bdev, NULL);
iterate_bdevs(fdatawrite_one_bdev, NULL);
iterate_bdevs(fdatawait_one_bdev, NULL);
if (unlikely(laptop_mode))
laptop_sync_completion();
return 0;
@ -125,10 +125,10 @@ static void do_sync_work(struct work_struct *work)
*/
iterate_supers(sync_inodes_one_sb, &nowait);
iterate_supers(sync_fs_one_sb, &nowait);
iterate_bdevs(flush_one_bdev, NULL);
iterate_bdevs(fdatawrite_one_bdev, NULL);
iterate_supers(sync_inodes_one_sb, &nowait);
iterate_supers(sync_fs_one_sb, &nowait);
iterate_bdevs(flush_one_bdev, NULL);
iterate_bdevs(fdatawrite_one_bdev, NULL);
printk("Emergency Sync complete\n");
kfree(work);
}