From: Zhang Yi <yi.zhang@huawei.com>
Date: Mon, 17 Feb 2025 06:59:55 +0000 (+0800)
Subject: jbd2: fix off-by-one while erasing journal
X-Git-Tag: v6.15-rc1~145^2~13
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=18aba2adb3e2a676fff0d81e51f5045f3c636666;p=thirdparty%2Fkernel%2Flinux.git

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: 01d5d96542fd ("ext4: add discard/zeroout flags to journal flush")
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250217065955.3829229-1-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index ff41a31e2bc9f..445f2bddd17cb 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -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;
 		}