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@linux.ibm.com>
Link: https://lore.kernel.org/r/5fc8e7788b924e211fcfa4a4c1d2f8503511661a.1589086800.git.riteshh@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index d1464d9..2e4697e 100644 (file)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2108,7 +2108,7 @@ 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;
@@ -2260,6 +2260,10 @@ repeat:
 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;
 }
 
@@ -3918,7 +3922,7 @@ 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)) {
@@ -3926,7 +3930,7 @@ 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);
@@ -3934,7 +3938,7 @@ 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)
@@ -3979,6 +3983,8 @@ repeat:
        /* 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;
        }
 
@@ -4003,6 +4009,9 @@ out:
        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;
 }
 
@@ -4538,6 +4547,7 @@ 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;
                }