Improve ext4 handling of ENOSPC with multi-threaded use-case

index 33a69424942c..decc5168d126 100644
@@ -349,6 +349,7 @@ static void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap,
 					ext4_group_t group);
 static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap,
 						ext4_group_t group);
+static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac);
 
 static inline void *mb_correct_addr_and_bit(int *bit, void *addr)
 {

@@ -1701,6 +1702,14 @@ static void ext4_mb_use_best_found(struct ext4_allocation_context *ac,
 		sbi->s_mb_last_start = ac->ac_f_ex.fe_start;
 		spin_unlock(&sbi->s_md_lock);
 	}
+	/*
+	 * As we've just preallocated more space than
+	 * user requested originally, we store allocated
+	 * space in a special descriptor.
+	 */
+	if (ac->ac_o_ex.fe_len < ac->ac_b_ex.fe_len)
+		ext4_mb_new_preallocation(ac);
+
 }
 
 /*

@@ -1949,7 +1958,7 @@ void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac,
 
 		ext4_mb_use_best_found(ac, e4b);
 
-		BUG_ON(ac->ac_b_ex.fe_len != ac->ac_g_ex.fe_len);
+		BUG_ON(ac->ac_f_ex.fe_len != ac->ac_g_ex.fe_len);
 
 		if (EXT4_SB(sb)->s_mb_stats)
 			atomic_inc(&EXT4_SB(sb)->s_bal_2orders);

@@ -3675,7 +3684,7 @@ static void ext4_mb_put_pa(struct ext4_allocation_context *ac,
 /*
  * creates new preallocated space for given inode
  */
-static noinline_for_stack int
+static noinline_for_stack void
 ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
 {
 	struct super_block *sb = ac->ac_sb;

@@ -3688,10 +3697,9 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
 	BUG_ON(ac->ac_o_ex.fe_len >= ac->ac_b_ex.fe_len);
 	BUG_ON(ac->ac_status != AC_STATUS_FOUND);
 	BUG_ON(!S_ISREG(ac->ac_inode->i_mode));
+	BUG_ON(ac->ac_pa == NULL);
 
-	pa = kmem_cache_alloc(ext4_pspace_cachep, GFP_NOFS);
-	if (pa == NULL)
-		return -ENOMEM;
+	pa = ac->ac_pa;
 
 	if (ac->ac_b_ex.fe_len < ac->ac_g_ex.fe_len) {
 		int winl;

@@ -3735,7 +3743,6 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
 	pa->pa_pstart = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
 	pa->pa_len = ac->ac_b_ex.fe_len;
 	pa->pa_free = pa->pa_len;
-	atomic_set(&pa->pa_count, 1);
 	spin_lock_init(&pa->pa_lock);
 	INIT_LIST_HEAD(&pa->pa_inode_list);
 	INIT_LIST_HEAD(&pa->pa_group_list);

@@ -3755,21 +3762,17 @@ ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
 	pa->pa_obj_lock = &ei->i_prealloc_lock;
 	pa->pa_inode = ac->ac_inode;
 
-	ext4_lock_group(sb, ac->ac_b_ex.fe_group);
 	list_add(&pa->pa_group_list, &grp->bb_prealloc_list);
-	ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
 
 	spin_lock(pa->pa_obj_lock);
 	list_add_rcu(&pa->pa_inode_list, &ei->i_prealloc_list);
 	spin_unlock(pa->pa_obj_lock);
-
-	return 0;
 }
 
 /*
  * creates new preallocated space for locality group inodes belongs to
  */
-static noinline_for_stack int
+static noinline_for_stack void
 ext4_mb_new_group_pa(struct ext4_allocation_context *ac)
 {
 	struct super_block *sb = ac->ac_sb;

@@ -3781,11 +3784,9 @@ ext4_mb_new_group_pa(struct ext4_allocation_context *ac)
 	BUG_ON(ac->ac_o_ex.fe_len >= ac->ac_b_ex.fe_len);
 	BUG_ON(ac->ac_status != AC_STATUS_FOUND);
 	BUG_ON(!S_ISREG(ac->ac_inode->i_mode));
+	BUG_ON(ac->ac_pa == NULL);
 
-	BUG_ON(ext4_pspace_cachep == NULL);
-	pa = kmem_cache_alloc(ext4_pspace_cachep, GFP_NOFS);
-	if (pa == NULL)
-		return -ENOMEM;
+	pa = ac->ac_pa;
 
 	/* preallocation can change ac_b_ex, thus we store actually
 	 * allocated blocks for history */

@@ -3795,7 +3796,6 @@ ext4_mb_new_group_pa(struct ext4_allocation_context *ac)
 	pa->pa_lstart = pa->pa_pstart;
 	pa->pa_len = ac->ac_b_ex.fe_len;
 	pa->pa_free = pa->pa_len;
-	atomic_set(&pa->pa_count, 1);
 	spin_lock_init(&pa->pa_lock);
 	INIT_LIST_HEAD(&pa->pa_inode_list);
 	INIT_LIST_HEAD(&pa->pa_group_list);

@@ -3816,26 +3816,20 @@ ext4_mb_new_group_pa(struct ext4_allocation_context *ac)
 	pa->pa_obj_lock = &lg->lg_prealloc_lock;
 	pa->pa_inode = NULL;
 
-	ext4_lock_group(sb, ac->ac_b_ex.fe_group);
 	list_add(&pa->pa_group_list, &grp->bb_prealloc_list);
-	ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
 
 	/*
 	 * We will later add the new pa to the right bucket
 	 * after updating the pa_free in ext4_mb_release_context
 	 */
-	return 0;
 }
 
-static int ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
+static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
 {
-	int err;
-
 	if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC)
-		err = ext4_mb_new_group_pa(ac);
+		ext4_mb_new_group_pa(ac);
 	else
-		err = ext4_mb_new_inode_pa(ac);
-	return err;
+		ext4_mb_new_inode_pa(ac);
 }
 
 /*

@@ -4150,6 +4144,29 @@ void ext4_discard_preallocations(struct inode *inode)
 	}
 }
 
+static int ext4_mb_pa_alloc(struct ext4_allocation_context *ac)
+{
+	struct ext4_prealloc_space *pa;
+
+	BUG_ON(ext4_pspace_cachep == NULL);
+	pa = kmem_cache_zalloc(ext4_pspace_cachep, GFP_NOFS);
+	if (!pa)
+		return -ENOMEM;
+	atomic_set(&pa->pa_count, 1);
+	ac->ac_pa = pa;
+	return 0;
+}
+
+static void ext4_mb_pa_free(struct ext4_allocation_context *ac)
+{
+	struct ext4_prealloc_space *pa = ac->ac_pa;
+
+	BUG_ON(!pa);
+	ac->ac_pa = NULL;
+	WARN_ON(!atomic_dec_and_test(&pa->pa_count));
+	kmem_cache_free(ext4_pspace_cachep, pa);
+}
+
 #ifdef CONFIG_EXT4_DEBUG
 static inline void ext4_mb_show_pa(struct super_block *sb)
 {

@@ -4606,23 +4623,28 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
 	if (!ext4_mb_use_preallocated(ac)) {
 		ac->ac_op = EXT4_MB_HISTORY_ALLOC;
 		ext4_mb_normalize_request(ac, ar);
+
+		*errp = ext4_mb_pa_alloc(ac);
+		if (*errp)
+			goto errout;
 repeat:
 		/* allocate space in core */
 		*errp = ext4_mb_regular_allocator(ac);
-		if (*errp)
-			goto discard_and_exit;
-
-		/* as we've just preallocated more space than
-		 * user requested originally, we store allocated
-		 * space in a special descriptor */
-		if (ac->ac_status == AC_STATUS_FOUND &&
-		    ac->ac_o_ex.fe_len < ac->ac_b_ex.fe_len)
-			*errp = ext4_mb_new_preallocation(ac);
+		/*
+		 * pa allocated above is added to grp->bb_prealloc_list only
+		 * when we were able to allocate some block i.e. when
+		 * ac->ac_status == AC_STATUS_FOUND.
+		 * And error from above mean ac->ac_status != AC_STATUS_FOUND
+		 * So we have to free this pa here itself.
+		 */
 		if (*errp) {
-		discard_and_exit:
+			ext4_mb_pa_free(ac);
 			ext4_discard_allocated_blocks(ac);
 			goto errout;
 		}
+		if (ac->ac_status == AC_STATUS_FOUND &&
+			ac->ac_o_ex.fe_len >= ac->ac_f_ex.fe_len)
+			ext4_mb_pa_free(ac);
 	}
 	if (likely(ac->ac_status == AC_STATUS_FOUND)) {
 		*errp = ext4_mb_mark_diskspace_used(ac, handle, reserv_clstrs);

@@ -4637,6 +4659,11 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
 		freed  = ext4_mb_discard_preallocations(sb, ac->ac_o_ex.fe_len);
 		if (freed)
 			goto repeat;
+		/*
+		 * If block allocation fails then the pa allocated above
+		 * needs to be freed here itself.
+		 */
+		ext4_mb_pa_free(ac);
 		*errp = -ENOSPC;
 	}
 

index decc5168d126..b75408d72773 100644
@@ -4543,6 +4543,17 @@ static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
 	return freed;
 }
 
+static bool ext4_mb_discard_preallocations_should_retry(struct super_block *sb,
+			struct ext4_allocation_context *ac)
+{
+	int freed;
+
+	freed = ext4_mb_discard_preallocations(sb, ac->ac_o_ex.fe_len);
+	if (freed)
+		return true;
+	return false;
+}
+
 /*
  * Main entry point into mballoc to allocate blocks
  * it tries to use preallocation first, then falls back

@@ -4551,7 +4562,6 @@ static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
 ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
 				struct ext4_allocation_request *ar, int *errp)
 {
-	int freed;
 	struct ext4_allocation_context *ac = NULL;
 	struct ext4_sb_info *sbi;
 	struct super_block *sb;

@@ -4656,8 +4666,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
 			ar->len = ac->ac_b_ex.fe_len;
 		}
 	} else {
-		freed  = ext4_mb_discard_preallocations(sb, ac->ac_o_ex.fe_len);
-		if (freed)
+		if (ext4_mb_discard_preallocations_should_retry(sb, ac))
 			goto repeat;
 		/*
 		 * If block allocation fails then the pa allocated above

index b75408d72773..754ff9f65199 100644
@@ -351,6 +351,35 @@ static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap,
 						ext4_group_t group);
 static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac);
 
+/*
+ * The algorithm using this percpu seq counter goes below:
+ * 1. We sample the percpu discard_pa_seq counter before trying for block
+ *    allocation in ext4_mb_new_blocks().
+ * 2. We increment this percpu discard_pa_seq counter when we either allocate
+ *    or free these blocks i.e. while marking those blocks as used/free in
+ *    mb_mark_used()/mb_free_blocks().
+ * 3. We also increment this percpu seq counter when we successfully identify
+ *    that the bb_prealloc_list is not empty and hence proceed for discarding
+ *    of those PAs inside ext4_mb_discard_group_preallocations().
+ *
+ * Now to make sure that the regular fast path of block allocation is not
+ * affected, as a small optimization we only sample the percpu seq counter
+ * on that cpu. Only when the block allocation fails and when freed blocks
+ * found were 0, that is when we sample percpu seq counter for all cpus using
+ * below function ext4_get_discard_pa_seq_sum(). This happens after making
+ * sure that all the PAs on grp->bb_prealloc_list got freed or if it's empty.
+ */
+static DEFINE_PER_CPU(u64, discard_pa_seq);
+static inline u64 ext4_get_discard_pa_seq_sum(void)
+{
+	int __cpu;
+	u64 __seq = 0;
+
+	for_each_possible_cpu(__cpu)
+		__seq += per_cpu(discard_pa_seq, __cpu);
+	return __seq;
+}
+
 static inline void *mb_correct_addr_and_bit(int *bit, void *addr)
 {
 #if BITS_PER_LONG == 64

@@ -1462,6 +1491,7 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
 	mb_check_buddy(e4b);
 	mb_free_blocks_double(inode, e4b, first, count);
 
+	this_cpu_inc(discard_pa_seq);
 	e4b->bd_info->bb_free += count;
 	if (first < e4b->bd_info->bb_first_free)
 		e4b->bd_info->bb_first_free = first;

@@ -1603,6 +1633,7 @@ static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex)
 	mb_check_buddy(e4b);
 	mb_mark_used_double(e4b, start, len);
 
+	this_cpu_inc(discard_pa_seq);
 	e4b->bd_info->bb_free -= len;
 	if (e4b->bd_info->bb_first_free == start)
 		e4b->bd_info->bb_first_free += len;

@@ -3962,6 +3993,7 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
 	INIT_LIST_HEAD(&list);
 repeat:
 	ext4_lock_group(sb, group);
+	this_cpu_inc(discard_pa_seq);
 	list_for_each_entry_safe(pa, tmp,
 				&grp->bb_prealloc_list, pa_group_list) {
 		spin_lock(&pa->pa_lock);

@@ -4544,14 +4576,26 @@ static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
 }
 
 static bool ext4_mb_discard_preallocations_should_retry(struct super_block *sb,
-			struct ext4_allocation_context *ac)
+			struct ext4_allocation_context *ac, u64 *seq)
 {
 	int freed;
+	u64 seq_retry = 0;
+	bool ret = false;
 
 	freed = ext4_mb_discard_preallocations(sb, ac->ac_o_ex.fe_len);
-	if (freed)
-		return true;
-	return false;
+	if (freed) {
+		ret = true;
+		goto out_dbg;
+	}
+	seq_retry = ext4_get_discard_pa_seq_sum();
+	if (seq_retry != *seq) {
+		*seq = seq_retry;
+		ret = true;
+	}
+
+out_dbg:
+	mb_debug(sb, "freed %d, retry ? %s\n", freed, ret ? "yes" : "no");
+	return ret;
 }
 
 /*

@@ -4568,6 +4612,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
 	ext4_fsblk_t block = 0;
 	unsigned int inquota = 0;
 	unsigned int reserv_clstrs = 0;
+	u64 seq;
 
 	might_sleep();
 	sb = ar->inode->i_sb;

@@ -4630,6 +4675,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
 	}
 
 	ac->ac_op = EXT4_MB_HISTORY_PREALLOC;
+	seq = *this_cpu_ptr(&discard_pa_seq);
 	if (!ext4_mb_use_preallocated(ac)) {
 		ac->ac_op = EXT4_MB_HISTORY_ALLOC;
 		ext4_mb_normalize_request(ac, ar);

@@ -4666,7 +4712,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
 			ar->len = ac->ac_b_ex.fe_len;
 		}
 	} else {
-		if (ext4_mb_discard_preallocations_should_retry(sb, ac))
+		if (ext4_mb_discard_preallocations_should_retry(sb, ac, &seq))
 			goto repeat;
 		/*
 		 * If block allocation fails then the pa allocated above

index 754ff9f65199..c9297c878a90 100644
@@ -2106,15 +2106,14 @@ void ext4_mb_scan_aligned(struct ext4_allocation_context *ac,
 }
 
 /*
- * This is now called BEFORE we load the buddy bitmap.
+ * This is also called BEFORE we load the buddy bitmap.
  * Returns either 1 or 0 indicating that the group is either suitable
- * for the allocation or not. In addition it can also return negative
- * error code when something goes wrong.
+ * for the allocation or not.
  */
-static int ext4_mb_good_group(struct ext4_allocation_context *ac,
+static bool ext4_mb_good_group(struct ext4_allocation_context *ac,
 				ext4_group_t group, int cr)
 {
-	unsigned free, fragments;
+	ext4_grpblk_t free, fragments;
 	int flex_size = ext4_flex_bg_size(EXT4_SB(ac->ac_sb));
 	struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group);
 

@@ -2122,23 +2121,16 @@ static int ext4_mb_good_group(struct ext4_allocation_context *ac,
 
 	free = grp->bb_free;
 	if (free == 0)
-		return 0;
+		return false;
 	if (cr <= 2 && free < ac->ac_g_ex.fe_len)
-		return 0;
+		return false;
 
 	if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp)))
-		return 0;
-
-	/* We only do this if the grp has never been initialized */
-	if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
-		int ret = ext4_mb_init_group(ac->ac_sb, group, GFP_NOFS);
-		if (ret)
-			return ret;
-	}
+		return false;
 
 	fragments = grp->bb_fragments;
 	if (fragments == 0)
-		return 0;
+		return false;
 
 	switch (cr) {
 	case 0:

@@ -2148,31 +2140,63 @@ static int ext4_mb_good_group(struct ext4_allocation_context *ac,
 		if ((ac->ac_flags & EXT4_MB_HINT_DATA) &&
 		    (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) &&
 		    ((group % flex_size) == 0))
-			return 0;
+			return false;
 
 		if ((ac->ac_2order > ac->ac_sb->s_blocksize_bits+1) ||
 		    (free / fragments) >= ac->ac_g_ex.fe_len)
-			return 1;
+			return true;
 
 		if (grp->bb_largest_free_order < ac->ac_2order)
-			return 0;
+			return false;
 
-		return 1;
+		return true;
 	case 1:
 		if ((free / fragments) >= ac->ac_g_ex.fe_len)
-			return 1;
+			return true;
 		break;
 	case 2:
 		if (free >= ac->ac_g_ex.fe_len)
-			return 1;
+			return true;
 		break;
 	case 3:
-		return 1;
+		return true;
 	default:
 		BUG();
 	}
 
-	return 0;
+	return false;
+}
+
+/*
+ * This could return negative error code if something goes wrong
+ * during ext4_mb_init_group(). This should not be called with
+ * ext4_lock_group() held.
+ */
+static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac,
+				     ext4_group_t group, int cr)
+{
+	struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group);
+	ext4_grpblk_t free;
+	int ret = 0;
+
+	free = grp->bb_free;
+	if (free == 0)
+		goto out;
+	if (cr <= 2 && free < ac->ac_g_ex.fe_len)
+		goto out;
+	if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp)))
+		goto out;
+
+	/* We only do this if the grp has never been initialized */
+	if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
+		ret = ext4_mb_init_group(ac->ac_sb, group, GFP_NOFS);
+		if (ret)
+			return ret;
+	}
+
+	ret = ext4_mb_good_group(ac, group, cr);
+out:
+	return ret;
 }
 
 static noinline_for_stack int

@@ -2260,7 +2284,7 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
 				group = 0;
 
 			/* This now checks without needing the buddy page */
-			ret = ext4_mb_good_group(ac, group, cr);
+			ret = ext4_mb_good_group_nolock(ac, group, cr);
 			if (ret <= 0) {
 				if (!first_err)
 					first_err = ret;

@@ -2278,11 +2302,9 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
 			 * block group
 			 */
 			ret = ext4_mb_good_group(ac, group, cr);
-			if (ret <= 0) {
+			if (ret == 0) {
 				ext4_unlock_group(sb, group);
 				ext4_mb_unload_buddy(&e4b);
-				if (!first_err)
-					first_err = ret;
 				continue;
 			}
 

index fb37fb3fe689..d185f3bcb9eb 100644
@@ -150,6 +150,8 @@ enum SHIFT_DIRECTION {
 #define EXT4_MB_USE_ROOT_BLOCKS		0x1000
 /* Use blocks from reserved pool */
 #define EXT4_MB_USE_RESERVED		0x2000
+/* Do strict check for free blocks while retrying block allocation */
+#define EXT4_MB_STRICT_CHECK		0x4000
 
 struct ext4_allocation_request {
 	/* target inode for block we're allocating */

index c9297c878a90..a9083113a8c0 100644
@@ -2176,9 +2176,13 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac,
 				     ext4_group_t group, int cr)
 {
 	struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group);
+	struct super_block *sb = ac->ac_sb;
+	bool should_lock = ac->ac_flags & EXT4_MB_STRICT_CHECK;
 	ext4_grpblk_t free;
 	int ret = 0;
 
+	if (should_lock)
+		ext4_lock_group(sb, group);
 	free = grp->bb_free;
 	if (free == 0)
 		goto out;

@@ -2186,6 +2190,8 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac,
 		goto out;
 	if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp)))
 		goto out;
+	if (should_lock)
+		ext4_unlock_group(sb, group);
 
 	/* We only do this if the grp has never been initialized */
 	if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {

@@ -2194,8 +2200,12 @@ static int ext4_mb_good_group_nolock(struct ext4_allocation_context *ac,
 			return ret;
 	}
 
+	if (should_lock)
+		ext4_lock_group(sb, group);
 	ret = ext4_mb_good_group(ac, group, cr);
 out:
+	if (should_lock)
+		ext4_unlock_group(sb, group);
 	return ret;
 }
 

@@ -4610,7 +4620,8 @@ static bool ext4_mb_discard_preallocations_should_retry(struct super_block *sb,
 		goto out_dbg;
 	}
 	seq_retry = ext4_get_discard_pa_seq_sum();
-	if (seq_retry != *seq) {
+	if (!(ac->ac_flags & EXT4_MB_STRICT_CHECK) || seq_retry != *seq) {
+		ac->ac_flags |= EXT4_MB_STRICT_CHECK;
 		*seq = seq_retry;
 		ret = true;
 	}

index 19c87661eeec..0df9efa80b16 100644
@@ -35,7 +35,8 @@ struct partial_cluster;
 	{ EXT4_MB_DELALLOC_RESERVED,	"DELALLOC_RESV" },	\
 	{ EXT4_MB_STREAM_ALLOC,		"STREAM_ALLOC" },	\
 	{ EXT4_MB_USE_ROOT_BLOCKS,	"USE_ROOT_BLKS" },	\
-	{ EXT4_MB_USE_RESERVED,		"USE_RESV" })
+	{ EXT4_MB_USE_RESERVED,		"USE_RESV" },		\
+	{ EXT4_MB_STRICT_CHECK,		"STRICT_CHECK" })
 
 #define show_map_flags(flags) __print_flags(flags, "|",			\
 	{ EXT4_GET_BLOCKS_CREATE,		"CREATE" },		\