[PATCH -V5] ext4: fix BUG when calling ext4_error with locked block group

Aneesh Kumar K.V
2008-12-02T06:10:37Z

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.

-V5 changes:
update ext4_commit_super to use the percpu free blocks and free inodes
counter values.

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 | 47 +++++++++++++++++++++++++++++++++++++++++++++++
fs/ext4/mballoc.c | 30 +++++++++++++++---------------
fs/ext4/mballoc.h | 47 -----------------------------------------------
fs/ext4/super.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
4 files changed, 105 insertions(+), 64 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index a5fa26e..44cd21c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1131,6 +1131,9 @@ 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);
@@ -1254,6 +1257,50 @@ 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 abb66a8..b1c216c 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)\n",
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\n",
group, free, grp->bb_free);
/*
@@ -1099,8 +1099,6 @@ 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;
@@ -1139,12 +1137,11 @@ __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)\n",
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]++;
@@ -1629,7 +1626,8 @@ 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\n",
free);
break;
@@ -1638,7 +1636,8 @@ 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\n",
free, ex.fe_len);
/*
@@ -3828,8 +3827,9 @@ 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\n",
- free, pa->pa_free);
+ ext4_grp_locked_error(sb, group,
+ __func__, "free %u, pa_free %u\n",
+ free, pa->pa_free);
/*
* pa is already deleted so we use the value obtained
* from the bitmap and continue.
@@ -4641,9 +4641,9 @@ 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)\n",
- block, entry->start_blk, entry->count);
+ ext4_grp_locked_error(sb, e4b->bd_group, __func__,
+ "Double free of blocks %d (%d %d)\n",
+ block, entry->start_blk, entry->count);
return 0;
}
}
diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index 997f78f..95d4c7f 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 7f188c1..8aef386 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -350,6 +350,44 @@ 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;
@@ -2820,8 +2858,11 @@ 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) {
--
1.6.1.rc1