Patch "ext4: set goal start correctly in ext4_mb_normalize_request" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ext4: set goal start correctly in ext4_mb_normalize_request

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ext4-set-goal-start-correctly-in-ext4_mb_normalize_r.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 672c3c18f362d07bd51d8d2ec501fe8062853923
Author: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
Date:   Sat Mar 4 01:21:01 2023 +0800

    ext4: set goal start correctly in ext4_mb_normalize_request
    
    [ Upstream commit b07ffe6927c75d99af534d685282ea188d9f71a6 ]
    
    We need to set ac_g_ex to notify the goal start used in
    ext4_mb_find_by_goal. Set ac_g_ex instead of ac_f_ex in
    ext4_mb_normalize_request.
    Besides we should assure goal start is in range [first_data_block,
    blocks_count) as ext4_mb_initialize_context does.
    
    [ Added a check to make sure size is less than ar->pright; otherwise
      we could end up passing an underflowed value of ar->pright - size to
      ext4_get_group_no_and_offset(), which will trigger a BUG_ON later on.
      - TYT ]
    
    Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
    Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@xxxxxxxxx>
    Link: https://lore.kernel.org/r/20230303172120.3800725-2-shikemeng@xxxxxxxxxxxxxxx
    Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 4cc635633f789..de51963c701f7 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4045,6 +4045,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
 				struct ext4_allocation_request *ar)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
+	struct ext4_super_block *es = sbi->s_es;
 	int bsbits, max;
 	ext4_lblk_t end;
 	loff_t size, start_off;
@@ -4225,18 +4226,21 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
 	ac->ac_g_ex.fe_len = EXT4_NUM_B2C(sbi, size);
 
 	/* define goal start in order to merge */
-	if (ar->pright && (ar->lright == (start + size))) {
+	if (ar->pright && (ar->lright == (start + size)) &&
+	    ar->pright >= size &&
+	    ar->pright - size >= le32_to_cpu(es->s_first_data_block)) {
 		/* merge to the right */
 		ext4_get_group_no_and_offset(ac->ac_sb, ar->pright - size,
-						&ac->ac_f_ex.fe_group,
-						&ac->ac_f_ex.fe_start);
+						&ac->ac_g_ex.fe_group,
+						&ac->ac_g_ex.fe_start);
 		ac->ac_flags |= EXT4_MB_HINT_TRY_GOAL;
 	}
-	if (ar->pleft && (ar->lleft + 1 == start)) {
+	if (ar->pleft && (ar->lleft + 1 == start) &&
+	    ar->pleft + 1 < ext4_blocks_count(es)) {
 		/* merge to the left */
 		ext4_get_group_no_and_offset(ac->ac_sb, ar->pleft + 1,
-						&ac->ac_f_ex.fe_group,
-						&ac->ac_f_ex.fe_start);
+						&ac->ac_g_ex.fe_group,
+						&ac->ac_g_ex.fe_start);
 		ac->ac_flags |= EXT4_MB_HINT_TRY_GOAL;
 	}