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 stable@vger.kernel.org.
Thanks, Sasha
------------------ original commit in Linus's tree ------------------
From 4fbf8bc733d14bceb16dda46a3f5e19c6a9621c5 Mon Sep 17 00:00:00 2001 From: Baokun Li libaokun1@huawei.com 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/3630fa7f-b432-7afd-5f79-781bc3b2c5ea@huawei.com Fixes: 93cdf49f6eca ("ext4: Fix best extent lstart adjustment logic in ext4_mb_new_inode_pa()") Cc: stable@kernel.org Signed-off-by: yangerkun yangerkun@huawei.com Signed-off-by: Baokun Li libaokun1@huawei.com Reviewed-by: Jan Kara jack@suse.cz Reviewed-by: Ojaswin Mujoo ojaswin@linux.ibm.com Link: https://lore.kernel.org/r/20240201141845.1879253-1-libaokun1@huawei.com Signed-off-by: Theodore Ts'o tytso@mit.edu --- 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); }