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>

1 files changed, 47 insertions, 0 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 8152b5603f0a..f0b1db6acf85 100644
--- a/fs/ext4/ext4.h
+++ b/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
  */