linux-ext4 - [RFC 05/20] ext4: mballoc: Add more mb

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Date:   Fri,  1 May 2020 11:59:47 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     linux-ext4@...r.kernel.org
Cc:     "Paul E . McKenney" <paulmck@...nel.org>,
        linux-fsdevel@...r.kernel.org, Jan Kara <jack@...e.com>,
        tytso@....edu, "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Ritesh Harjani <riteshh@...ux.ibm.com>
Subject: [RFC 05/20] ext4: mballoc: Add more mb_debug() msgs

This patch adds some more debugging mb_debug() msgs to help improve
mballoc code debugging.
Other than adding more mb_debug() msgs at few more places,
there should be no other functionality change in this patch.

Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com>
---
 fs/ext4/mballoc.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index d7ae5a092796..2acabc3927e0 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2137,7 +2137,7 @@ static noinline_for_stack int
 ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
 {
 	ext4_group_t ngroups, group, i;
-	int cr;
+	int cr = -1;
 	int err = 0, first_err = 0;
 	struct ext4_sb_info *sbi;
 	struct super_block *sb;
@@ -2289,6 +2289,10 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
 out:
 	if (!err && ac->ac_status != AC_STATUS_FOUND && first_err)
 		err = first_err;
+
+	mb_debug(1, "Best len %d, origin len %d, ac_status %u, ac_flags 0x%x, cr %d ret %d\n",
+		 ac->ac_b_ex.fe_len, ac->ac_o_ex.fe_len, ac->ac_status,
+		 ac->ac_flags, cr, err);
 	return err;
 }
 
@@ -3949,7 +3953,7 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
 	mb_debug(1, "discard preallocation for group %u\n", group);
 
 	if (list_empty(&grp->bb_prealloc_list))
-		return 0;
+		goto out_dbg;
 
 	bitmap_bh = ext4_read_block_bitmap(sb, group);
 	if (IS_ERR(bitmap_bh)) {
@@ -3957,7 +3961,7 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
 		ext4_error_err(sb, -err,
 			       "Error %d reading block bitmap for %u",
 			       err, group);
-		return 0;
+		goto out_dbg;
 	}
 
 	err = ext4_mb_load_buddy(sb, group, &e4b);
@@ -3965,7 +3969,7 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
 		ext4_warning(sb, "Error %d loading buddy information for %u",
 			     err, group);
 		put_bh(bitmap_bh);
-		return 0;
+		goto out_dbg;
 	}
 
 	if (needed == 0)
@@ -4011,6 +4015,8 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
 	/* found anything to free? */
 	if (list_empty(&list)) {
 		BUG_ON(free != 0);
+		mb_debug(1, "Someone else may have freed PA for this group %u\n",
+			 group);
 		goto out;
 	}
 
@@ -4035,6 +4041,9 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
 	ext4_unlock_group(sb, group);
 	ext4_mb_unload_buddy(&e4b);
 	put_bh(bitmap_bh);
+out_dbg:
+	mb_debug(1, "discarded (%d) blocks preallocated for group %u bb_free (%d)\n",
+		 free, group, grp->bb_free);
 	return free;
 }
 
@@ -4602,6 +4611,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
 			ar->len = ar->len >> 1;
 		}
 		if (!ar->len) {
+			ext4_mb_show_pa(sb);
 			*errp = -ENOSPC;
 			return 0;
 		}
-- 
2.21.0