Commit 3cb0929a authored by Wang Shilong's avatar Wang Shilong Committed by Chris Mason
Browse files

Btrfs: fix wrong super generation mismatch when scrubbing supers 



We came a race condition when scrubbing superblocks, the story is:

In commiting transaction, we will update @last_trans_commited after
writting superblocks, if scrubber start after writting superblocks
and before updating @last_trans_commited, generation mismatch happens!

We fix this by checking @scrub_pause_req, and we won't start a srubber
until commiting transaction is finished.(after btrfs_scrub_continue()
finished.)

Reported-by: default avatarSebastian Ochmann <ochmann@informatik.uni-bonn.de>
Signed-off-by: default avatarWang Shilong <wangsl.fnst@cn.fujitsu.com>
Reviewed-by: default avatarMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fb.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 5a0f4e2c

fs/btrfs/scrub.c

+26 −19
Original line number Diff line number Diff line
@@ -256,6 +256,7 @@ static int copy_nocow_pages_for_inode(u64 inum, u64 offset, u64 root, 
static int copy_nocow_pages(struct scrub_ctx *sctx, u64 logical, u64 len,

			    int mirror_num, u64 physical_for_dev_replace);

static void copy_nocow_pages_worker(struct btrfs_work *work);

static void scrub_blocked_if_needed(struct btrfs_fs_info *fs_info);





static void scrub_pending_bio_inc(struct scrub_ctx *sctx)
@@ -269,6 +270,16 @@ static void scrub_pending_bio_dec(struct scrub_ctx *sctx) 
	wake_up(&sctx->list_wait);

}



static void scrub_blocked_if_needed(struct btrfs_fs_info *fs_info)

{

	while (atomic_read(&fs_info->scrub_pause_req)) {

		mutex_unlock(&fs_info->scrub_lock);

		wait_event(fs_info->scrub_pause_wait,

		   atomic_read(&fs_info->scrub_pause_req) == 0);

		mutex_lock(&fs_info->scrub_lock);

	}

}



/*

 * used for workers that require transaction commits (i.e., for the

 * NOCOW case)
@@ -2310,14 +2321,10 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx, 
		btrfs_reada_wait(reada2);



	mutex_lock(&fs_info->scrub_lock);

	while (atomic_read(&fs_info->scrub_pause_req)) {

		mutex_unlock(&fs_info->scrub_lock);

		wait_event(fs_info->scrub_pause_wait,

		   atomic_read(&fs_info->scrub_pause_req) == 0);

		mutex_lock(&fs_info->scrub_lock);

	}

	scrub_blocked_if_needed(fs_info);

	atomic_dec(&fs_info->scrubs_paused);

	mutex_unlock(&fs_info->scrub_lock);



	wake_up(&fs_info->scrub_pause_wait);



	/*
@@ -2357,15 +2364,12 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx, 
			atomic_set(&sctx->wr_ctx.flush_all_writes, 0);

			atomic_inc(&fs_info->scrubs_paused);

			wake_up(&fs_info->scrub_pause_wait);



			mutex_lock(&fs_info->scrub_lock);

			while (atomic_read(&fs_info->scrub_pause_req)) {

				mutex_unlock(&fs_info->scrub_lock);

				wait_event(fs_info->scrub_pause_wait,

				   atomic_read(&fs_info->scrub_pause_req) == 0);

				mutex_lock(&fs_info->scrub_lock);

			}

			scrub_blocked_if_needed(fs_info);

			atomic_dec(&fs_info->scrubs_paused);

			mutex_unlock(&fs_info->scrub_lock);



			wake_up(&fs_info->scrub_pause_wait);

		}
@@ -2687,14 +2691,10 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx, 
			   atomic_read(&sctx->workers_pending) == 0);



		mutex_lock(&fs_info->scrub_lock);

		while (atomic_read(&fs_info->scrub_pause_req)) {

			mutex_unlock(&fs_info->scrub_lock);

			wait_event(fs_info->scrub_pause_wait,

			   atomic_read(&fs_info->scrub_pause_req) == 0);

			mutex_lock(&fs_info->scrub_lock);

		}

		scrub_blocked_if_needed(fs_info);

		atomic_dec(&fs_info->scrubs_paused);

		mutex_unlock(&fs_info->scrub_lock);



		wake_up(&fs_info->scrub_pause_wait);



		btrfs_put_block_group(cache);
@@ -2906,7 +2906,13 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start, 
	}

	sctx->readonly = readonly;

	dev->scrub_device = sctx;

	mutex_unlock(&fs_info->fs_devices->device_list_mutex);



	/*

	 * checking @scrub_pause_req here, we can avoid

	 * race between committing transaction and scrubbing.

	 */

	scrub_blocked_if_needed(fs_info);

	atomic_inc(&fs_info->scrubs_running);

	mutex_unlock(&fs_info->scrub_lock);
@@ -2915,9 +2921,10 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start, 
		 * by holding device list mutex, we can

		 * kick off writing super in log tree sync.

		 */

		mutex_lock(&fs_info->fs_devices->device_list_mutex);

		ret = scrub_supers(sctx, dev);

	}

		mutex_unlock(&fs_info->fs_devices->device_list_mutex);

	}



	if (!ret)

		ret = scrub_enumerate_chunks(sctx, dev, start, end,

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