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Commit 2e3c2513 authored by Qu Wenruo's avatar Qu Wenruo Committed by David Sterba
Browse files

btrfs: extent_io: add proper error handling to lock_extent_buffer_for_io() 



This function needs some extra checks on locked pages and eb.  For error
handling we need to unlock locked pages and the eb.

There is a rare >0 return value branch, where all pages get locked
while write bio is not flushed.

Thankfully it's handled by the only caller, btree_write_cache_pages(),
as later write_one_eb() call will trigger submit_one_bio().  So there
shouldn't be any problem.

Signed-off-by: default avatarQu Wenruo <wqu@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 02c6db4f

fs/btrfs/extent_io.c

+22 −5
Original line number Diff line number Diff line
@@ -3492,19 +3492,27 @@ void wait_on_extent_buffer_writeback(struct extent_buffer *eb) 
		       TASK_UNINTERRUPTIBLE);

}



/*

 * Lock eb pages and flush the bio if we can't the locks

 *

 * Return  0 if nothing went wrong

 * Return >0 is same as 0, except bio is not submitted

 * Return <0 if something went wrong, no page is locked

 */

static noinline_for_stack int

lock_extent_buffer_for_io(struct extent_buffer *eb,

			  struct btrfs_fs_info *fs_info,

			  struct extent_page_data *epd)

{

	int i, num_pages;

	int i, num_pages, failed_page_nr;

	int flush = 0;

	int ret = 0;



	if (!btrfs_try_tree_write_lock(eb)) {

		flush = 1;

		ret = flush_write_bio(epd);

		BUG_ON(ret < 0);

		if (ret < 0)

			return ret;

		flush = 1;

		btrfs_tree_lock(eb);

	}
@@ -3514,7 +3522,8 @@ lock_extent_buffer_for_io(struct extent_buffer *eb, 
			return 0;

		if (!flush) {

			ret = flush_write_bio(epd);

			BUG_ON(ret < 0);

			if (ret < 0)

				return ret;

			flush = 1;

		}

		while (1) {
@@ -3556,7 +3565,10 @@ lock_extent_buffer_for_io(struct extent_buffer *eb, 
		if (!trylock_page(p)) {

			if (!flush) {

				ret = flush_write_bio(epd);

				BUG_ON(ret < 0);

				if (ret < 0) {

					failed_page_nr = i;

					goto err_unlock;

				}

				flush = 1;

			}

			lock_page(p);
@@ -3564,6 +3576,11 @@ lock_extent_buffer_for_io(struct extent_buffer *eb, 
	}



	return ret;

err_unlock:

	/* Unlock already locked pages */

	for (i = 0; i < failed_page_nr; i++)

		unlock_page(eb->pages[i]);

	return ret;

}



static void end_extent_buffer_writeback(struct extent_buffer *eb)