The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <[email protected]>.
Thanks,
Sasha
------------------ original commit in Linus's tree ------------------
From 4fbf8bc733d14bceb16dda46a3f5e19c6a9621c5 Mon Sep 17 00:00:00 2001
From: Baokun Li <[email protected]>
Date: Thu, 1 Feb 2024 22:18:45 +0800
Subject: [PATCH] ext4: correct best extent lstart adjustment logic
When yangerkun review commit 93cdf49f6eca ("ext4: Fix best extent lstart
adjustment logic in ext4_mb_new_inode_pa()"), it was found that the best
extent did not completely cover the original request after adjusting the
best extent lstart in ext4_mb_new_inode_pa() as follows:
original request: 2/10(8)
normalized request: 0/64(64)
best extent: 0/9(9)
When we check if best ex can be kept at start of goal, ac_o_ex.fe_logical
is 2 less than the adjusted best extent logical end 9, so we think the
adjustment is done. But obviously 0/9(9) doesn't cover 2/10(8), so we
should determine here if the original request logical end is less than or
equal to the adjusted best extent logical end.
In addition, add a comment stating when adjusted best_ex will not cover
the original request, and remove the duplicate assertion because adjusting
lstart makes no change to b_ex.fe_len.
Link: https://lore.kernel.org/r/[email protected]
Fixes: 93cdf49f6eca ("ext4: Fix best extent lstart adjustment logic in ext4_mb_new_inode_pa()")
Cc: <[email protected]>
Signed-off-by: yangerkun <[email protected]>
Signed-off-by: Baokun Li <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Reviewed-by: Ojaswin Mujoo <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>
---
fs/ext4/mballoc.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index bce82e1e792fd..bd26f2a907512 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -5172,10 +5172,16 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
.fe_len = ac->ac_orig_goal_len,
};
loff_t orig_goal_end = extent_logical_end(sbi, &ex);
+ loff_t o_ex_end = extent_logical_end(sbi, &ac->ac_o_ex);
- /* we can't allocate as much as normalizer wants.
- * so, found space must get proper lstart
- * to cover original request */
+ /*
+ * We can't allocate as much as normalizer wants, so we try
+ * to get proper lstart to cover the original request, except
+ * when the goal doesn't cover the original request as below:
+ *
+ * orig_ex:2045/2055(10), isize:8417280 -> normalized:0/2048
+ * best_ex:0/200(200) -> adjusted: 1848/2048(200)
+ */
BUG_ON(ac->ac_g_ex.fe_logical > ac->ac_o_ex.fe_logical);
BUG_ON(ac->ac_g_ex.fe_len < ac->ac_o_ex.fe_len);
@@ -5187,7 +5193,7 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
* 1. Check if best ex can be kept at end of goal (before
* cr_best_avail trimmed it) and still cover original start
* 2. Else, check if best ex can be kept at start of goal and
- * still cover original start
+ * still cover original end
* 3. Else, keep the best ex at start of original request.
*/
ex.fe_len = ac->ac_b_ex.fe_len;
@@ -5197,7 +5203,7 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
goto adjust_bex;
ex.fe_logical = ac->ac_g_ex.fe_logical;
- if (ac->ac_o_ex.fe_logical < extent_logical_end(sbi, &ex))
+ if (o_ex_end <= extent_logical_end(sbi, &ex))
goto adjust_bex;
ex.fe_logical = ac->ac_o_ex.fe_logical;
@@ -5205,7 +5211,6 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
ac->ac_b_ex.fe_logical = ex.fe_logical;
BUG_ON(ac->ac_o_ex.fe_logical < ac->ac_b_ex.fe_logical);
- BUG_ON(ac->ac_o_ex.fe_len > ac->ac_b_ex.fe_len);
BUG_ON(extent_logical_end(sbi, &ex) > orig_goal_end);
}
--
2.43.0