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>

4 files changed, 105 insertions, 64 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
  */
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 0bf4c4c06b19..cda69632eea3 100644
--- a/fs/ext4/mballoc.c
+++ b/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;
                 }
         }
diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index 997f78fff129..95d4c7f29a8a 100644
--- a/fs/ext4/mballoc.h
+++ b/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)
 {
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index a9dd1170bfea..2415e2b09707 100644
--- a/fs/ext4/super.c
+++ b/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) {