linux-ext4 - [PATCH 6/8] ext4: add EXT4_MB_HINT_GOAL_ONLY test in ext4_mb_use

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Date:   Wed, 22 Mar 2023 00:12:18 +0800
From:   Kemeng Shi <shikemeng@...weicloud.com>
To:     tytso@....edu, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     ojaswin@...ux.ibm.com, shikemeng@...weicloud.com
Subject: [PATCH 6/8] ext4: add EXT4_MB_HINT_GOAL_ONLY test in ext4_mb_use_preallocated

ext4_mb_use_preallocated will ignore the demand to alloc goal blocks,
although the EXT4_MB_HINT_GOAL_ONLY is requested.
For group pa, ext4_mb_group_or_file will not set EXT4_MB_HINT_GROUP_ALLOC
if EXT4_MB_HINT_GOAL_ONLY is set. So we will not alloc goal blocks from
group pa if EXT4_MB_HINT_GOAL_ONLY is set.
For inode pa, ext4_mb_pa_goal_check is added to check if free extent in
found inode pa meets goal blocks when EXT4_MB_HINT_GOAL_ONLY is set.

Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
Suggested-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
---
 fs/ext4/mballoc.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index b963111eeec6..5b837918c624 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4351,6 +4351,37 @@ ext4_mb_check_group_pa(ext4_fsblk_t goal_block,
 	return pa;
 }
 
+/*
+ * check if found pa meets EXT4_MB_HINT_GOAL_ONLY
+ */
+static bool
+ext4_mb_pa_goal_check(struct ext4_allocation_context *ac,
+		      struct ext4_prealloc_space *pa)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
+	ext4_fsblk_t start;
+
+	if (likely(!(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY)))
+		return true;
+
+	/*
+	 * If EXT4_MB_HINT_GOAL_ONLY is set, ac_g_ex will not be adjusted
+	 * in ext4_mb_normalize_request and will keep same with ac_o_ex
+	 * from ext4_mb_initialize_context. Choose ac_g_ex here to keep
+	 * consistent with ext4_mb_find_by_goal.
+	 */
+	start = pa->pa_pstart +
+		(ac->ac_g_ex.fe_logical - pa->pa_lstart);
+	if (ext4_grp_offs_to_block(ac->ac_sb, &ac->ac_g_ex) != start)
+		return false;
+
+	if (ac->ac_g_ex.fe_len > pa->pa_len -
+	    EXT4_B2C(sbi, ac->ac_g_ex.fe_logical - pa->pa_lstart))
+		return false;
+
+	return true;
+}
+
 /*
  * search goal blocks in preallocated space
  */
@@ -4387,7 +4418,8 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
 
 		/* found preallocated blocks, use them */
 		spin_lock(&pa->pa_lock);
-		if (pa->pa_deleted == 0 && pa->pa_free) {
+		if (pa->pa_deleted == 0 && pa->pa_free &&
+		    likely(ext4_mb_pa_goal_check(ac, pa))) {
 			atomic_inc(&pa->pa_count);
 			ext4_mb_use_inode_pa(ac, pa);
 			spin_unlock(&pa->pa_lock);
-- 
2.30.0