ext4: fix BUG when calling ext4_error with locked block group

The mballoc code likes to call ext4_error while it is holding locked
block groups.  This can causes a scheduling in atomic context BUG.  We
can't just unlock the block group and relock it after/if ext4_error
returns since that might result in race conditions in the case where
the filesystem is set to continue after finding errors.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -1126,6 +1126,9 @@ extern void ext4_abort(struct super_block *, const char *, const char *, ...)
 	__attribute__ ((format (printf, 3, 4)));
 extern void ext4_warning(struct super_block *, const char *, const char *, ...)
 	__attribute__ ((format (printf, 3, 4)));
+extern void ext4_grp_locked_error(struct super_block *, ext4_group_t,
+				const char *, const char *, ...)
+	__attribute__ ((format (printf, 4, 5)));
 extern void ext4_update_dynamic_rev(struct super_block *sb);
 extern int ext4_update_compat_feature(handle_t *handle, struct super_block *sb,
 					__u32 compat);
@@ -1249,6 +1252,50 @@ static inline void ext4_update_i_disksize(struct inode *inode, loff_t newsize)
 	return ;
 }
 
+struct ext4_group_info {
+	unsigned long   bb_state;
+	struct rb_root  bb_free_root;
+	unsigned short  bb_first_free;
+	unsigned short  bb_free;
+	unsigned short  bb_fragments;
+	struct          list_head bb_prealloc_list;
+#ifdef DOUBLE_CHECK
+	void            *bb_bitmap;
+#endif
+	struct rw_semaphore alloc_sem;
+	unsigned short  bb_counters[];
+};
+
+#define EXT4_GROUP_INFO_NEED_INIT_BIT	0
+#define EXT4_GROUP_INFO_LOCKED_BIT	1
+
+#define EXT4_MB_GRP_NEED_INIT(grp)	\
+	(test_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &((grp)->bb_state)))
+
+static inline void ext4_lock_group(struct super_block *sb, ext4_group_t group)
+{
+	struct ext4_group_info *grinfo = ext4_get_group_info(sb, group);
+
+	bit_spin_lock(EXT4_GROUP_INFO_LOCKED_BIT, &(grinfo->bb_state));
+}
+
+static inline void ext4_unlock_group(struct super_block *sb,
+					ext4_group_t group)
+{
+	struct ext4_group_info *grinfo = ext4_get_group_info(sb, group);
+
+	bit_spin_unlock(EXT4_GROUP_INFO_LOCKED_BIT, &(grinfo->bb_state));
+}
+
+static inline int ext4_is_group_locked(struct super_block *sb,
+					ext4_group_t group)
+{
+	struct ext4_group_info *grinfo = ext4_get_group_info(sb, group);
+
+	return bit_spin_is_locked(EXT4_GROUP_INFO_LOCKED_BIT,
+						&(grinfo->bb_state));
+}
+
 /*
  * Inodes and files operations
  */

fs/ext4/mballoc.c

@@ -457,8 +457,8 @@ static void mb_free_blocks_double(struct inode *inode, struct ext4_buddy *e4b,
 			blocknr += first + i;
 			blocknr +=
 			    le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block);
-
-			ext4_error(sb, __func__, "double-free of inode"
+			ext4_grp_locked_error(sb, e4b->bd_group,
+				   __func__, "double-free of inode"
 				   " %lu's block %llu(bit %u in group %u)",
 				   inode ? inode->i_ino : 0, blocknr,
 				   first + i, e4b->bd_group);
@@ -702,7 +702,7 @@ static void ext4_mb_generate_buddy(struct super_block *sb,
 	grp->bb_fragments = fragments;
 
 	if (free != grp->bb_free) {
-		ext4_error(sb, __func__,
+		ext4_grp_locked_error(sb, group,  __func__,
 			"EXT4-fs: group %u: %u blocks in bitmap, %u in gd",
 			group, free, grp->bb_free);
 		/*
@@ -1095,8 +1095,6 @@ static void mb_set_bits(spinlock_t *lock, void *bm, int cur, int len)
 
 static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
 			  int first, int count)
-__releases(bitlock)
-__acquires(bitlock)
 {
 	int block = 0;
 	int max = 0;
@@ -1135,12 +1133,11 @@ __acquires(bitlock)
 			blocknr += block;
 			blocknr +=
 			    le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block);
-			ext4_unlock_group(sb, e4b->bd_group);
-			ext4_error(sb, __func__, "double-free of inode"
+			ext4_grp_locked_error(sb, e4b->bd_group,
+				   __func__, "double-free of inode"
 				   " %lu's block %llu(bit %u in group %u)",
 				   inode ? inode->i_ino : 0, blocknr, block,
 				   e4b->bd_group);
-			ext4_lock_group(sb, e4b->bd_group);
 		}
 		mb_clear_bit(block, EXT4_MB_BITMAP(e4b));
 		e4b->bd_info->bb_counters[order]++;
@@ -1623,7 +1620,8 @@ static void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
 			 * free blocks even though group info says we
 			 * we have free blocks
 			 */
-			ext4_error(sb, __func__, "%d free blocks as per "
+			ext4_grp_locked_error(sb, e4b->bd_group,
+					__func__, "%d free blocks as per "
 					"group info. But bitmap says 0",
 					free);
 			break;
@@ -1632,7 +1630,8 @@ static void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
 		mb_find_extent(e4b, 0, i, ac->ac_g_ex.fe_len, &ex);
 		BUG_ON(ex.fe_len <= 0);
 		if (free < ex.fe_len) {
-			ext4_error(sb, __func__, "%d free blocks as per "
+			ext4_grp_locked_error(sb, e4b->bd_group,
+					__func__, "%d free blocks as per "
 					"group info. But got %d blocks",
 					free, ex.fe_len);
 			/*
@@ -3822,8 +3821,9 @@ ext4_mb_release_inode_pa(struct ext4_buddy *e4b, struct buffer_head *bitmap_bh,
 			pa, (unsigned long) pa->pa_lstart,
 			(unsigned long) pa->pa_pstart,
 			(unsigned long) pa->pa_len);
-		ext4_error(sb, __func__, "free %u, pa_free %u",
-						free, pa->pa_free);
+		ext4_grp_locked_error(sb, group,
+					__func__, "free %u, pa_free %u",
+					free, pa->pa_free);
 		/*
 		 * pa is already deleted so we use the value obtained
 		 * from the bitmap and continue.
@@ -4633,9 +4633,9 @@ ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,
 		else if (block >= (entry->start_blk + entry->count))
 			n = &(*n)->rb_right;
 		else {
-			ext4_error(sb, __func__,
-			    "Double free of blocks %d (%d %d)",
-			    block, entry->start_blk, entry->count);
+			ext4_grp_locked_error(sb, e4b->bd_group, __func__,
+					"Double free of blocks %d (%d %d)",
+					block, entry->start_blk, entry->count);
 			return 0;
 		}
 	}

fs/ext4/mballoc.h

@@ -118,27 +118,6 @@ struct ext4_free_data {
 	tid_t	t_tid;
 };
 
-struct ext4_group_info {
-	unsigned long	bb_state;
-	struct rb_root  bb_free_root;
-	unsigned short	bb_first_free;
-	unsigned short	bb_free;
-	unsigned short	bb_fragments;
-	struct		list_head bb_prealloc_list;
-#ifdef DOUBLE_CHECK
-	void		*bb_bitmap;
-#endif
-	struct rw_semaphore alloc_sem;
-	unsigned short	bb_counters[];
-};
-
-#define EXT4_GROUP_INFO_NEED_INIT_BIT	0
-#define EXT4_GROUP_INFO_LOCKED_BIT	1
-
-#define EXT4_MB_GRP_NEED_INIT(grp)	\
-	(test_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &((grp)->bb_state)))
-
-
 struct ext4_prealloc_space {
 	struct list_head	pa_inode_list;
 	struct list_head	pa_group_list;
@@ -264,32 +243,6 @@ static inline void ext4_mb_store_history(struct ext4_allocation_context *ac)
 #define in_range(b, first, len)	((b) >= (first) && (b) <= (first) + (len) - 1)
 
 struct buffer_head *read_block_bitmap(struct super_block *, ext4_group_t);
-
-
-static inline void ext4_lock_group(struct super_block *sb, ext4_group_t group)
-{
-	struct ext4_group_info *grinfo = ext4_get_group_info(sb, group);
-
-	bit_spin_lock(EXT4_GROUP_INFO_LOCKED_BIT, &(grinfo->bb_state));
-}
-
-static inline void ext4_unlock_group(struct super_block *sb,
-					ext4_group_t group)
-{
-	struct ext4_group_info *grinfo = ext4_get_group_info(sb, group);
-
-	bit_spin_unlock(EXT4_GROUP_INFO_LOCKED_BIT, &(grinfo->bb_state));
-}
-
-static inline int ext4_is_group_locked(struct super_block *sb,
-					ext4_group_t group)
-{
-	struct ext4_group_info *grinfo = ext4_get_group_info(sb, group);
-
-	return bit_spin_is_locked(EXT4_GROUP_INFO_LOCKED_BIT,
-						&(grinfo->bb_state));
-}
-
 static inline ext4_fsblk_t ext4_grp_offs_to_block(struct super_block *sb,
 					struct ext4_free_extent *fex)
 {

fs/ext4/super.c

@@ -366,6 +366,44 @@ void ext4_warning(struct super_block *sb, const char *function,
 	va_end(args);
 }
 
+void ext4_grp_locked_error(struct super_block *sb, ext4_group_t grp,
+				const char *function, const char *fmt, ...)
+__releases(bitlock)
+__acquires(bitlock)
+{
+	va_list args;
+	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
+
+	va_start(args, fmt);
+	printk(KERN_CRIT "EXT4-fs error (device %s): %s: ", sb->s_id, function);
+	vprintk(fmt, args);
+	printk("\n");
+	va_end(args);
+
+	if (test_opt(sb, ERRORS_CONT)) {
+		EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
+		es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
+		ext4_commit_super(sb, es, 0);
+		return;
+	}
+	ext4_unlock_group(sb, grp);
+	ext4_handle_error(sb);
+	/*
+	 * We only get here in the ERRORS_RO case; relocking the group
+	 * may be dangerous, but nothing bad will happen since the
+	 * filesystem will have already been marked read/only and the
+	 * journal has been aborted.  We return 1 as a hint to callers
+	 * who might what to use the return value from
+	 * ext4_grp_locked_error() to distinguish beween the
+	 * ERRORS_CONT and ERRORS_RO case, and perhaps return more
+	 * aggressively from the ext4 function in question, with a
+	 * more appropriate error code.
+	 */
+	ext4_lock_group(sb, grp);
+	return;
+}
+
+
 void ext4_update_dynamic_rev(struct super_block *sb)
 {
 	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
@@ -2868,8 +2906,11 @@ static void ext4_commit_super(struct super_block *sb,
 		set_buffer_uptodate(sbh);
 	}
 	es->s_wtime = cpu_to_le32(get_seconds());
-	ext4_free_blocks_count_set(es, ext4_count_free_blocks(sb));
-	es->s_free_inodes_count = cpu_to_le32(ext4_count_free_inodes(sb));
+	ext4_free_blocks_count_set(es, percpu_counter_sum_positive(
+					&EXT4_SB(sb)->s_freeblocks_counter));
+	es->s_free_inodes_count = cpu_to_le32(percpu_counter_sum_positive(
+					&EXT4_SB(sb)->s_freeinodes_counter));
+
 	BUFFER_TRACE(sbh, "marking dirty");
 	mark_buffer_dirty(sbh);
 	if (sync) {