Commit 18aba2ad authored by Zhang Yi's avatar Zhang Yi Committed by Theodore Ts'o
Browse files

jbd2: fix off-by-one while erasing journal 



In __jbd2_journal_erase(), the block_stop parameter includes the last
block of a contiguous region; however, the calculation of byte_stop is
incorrect, as it does not account for the bytes in that last block.
Consequently, the page cache is not cleared properly, which occasionally
causes the ext4/050 test to fail.

Since block_stop operates on inclusion semantics, it involves repeated
increments and decrements by 1, significantly increasing the complexity
of the calculations. Optimize the calculation and fix the incorrect
byte_stop by make both block_stop and byte_stop to use exclusion
semantics.

This fixes a failure in fstests ext4/050.

Fixes: 01d5d965 ("ext4: add discard/zeroout flags to journal flush")
Signed-off-by: default avatarZhang Yi <yi.zhang@huawei.com>
Reviewed-by: default avatarBaokun Li <libaokun1@huawei.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250217065955.3829229-1-yi.zhang@huaweicloud.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 08be56fe

fs/jbd2/journal.c

+6 −9
Original line number Diff line number Diff line
@@ -1964,17 +1964,15 @@ static int __jbd2_journal_erase(journal_t *journal, unsigned int flags) 
			return err;

		}



		if (block_start == ~0ULL) {

			block_start = phys_block;

			block_stop = block_start - 1;

		}

		if (block_start == ~0ULL)

			block_stop = block_start = phys_block;



		/*

		 * last block not contiguous with current block,

		 * process last contiguous region and return to this block on

		 * next loop

		 */

		if (phys_block != block_stop + 1) {

		if (phys_block != block_stop) {

			block--;

		} else {

			block_stop++;
@@ -1993,11 +1991,10 @@ static int __jbd2_journal_erase(journal_t *journal, unsigned int flags) 
		 */

		byte_start = block_start * journal->j_blocksize;

		byte_stop = block_stop * journal->j_blocksize;

		byte_count = (block_stop - block_start + 1) *

				journal->j_blocksize;

		byte_count = (block_stop - block_start) * journal->j_blocksize;



		truncate_inode_pages_range(journal->j_dev->bd_mapping,

				byte_start, byte_stop);

				byte_start, byte_stop - 1);



		if (flags & JBD2_JOURNAL_FLUSH_DISCARD) {

			err = blkdev_issue_discard(journal->j_dev,
@@ -2012,7 +2009,7 @@ static int __jbd2_journal_erase(journal_t *journal, unsigned int flags) 
		}



		if (unlikely(err != 0)) {

			pr_err("JBD2: (error %d) unable to wipe journal at physical blocks %llu - %llu",

			pr_err("JBD2: (error %d) unable to wipe journal at physical blocks [%llu, %llu)",

					err, block_start, block_stop);

			return err;

		}