Re: ENOSPC returned during writepages

Aneesh Kumar K.V
2008-08-21T16:46:01Z

On Wed, Aug 20, 2008 at 11:13:39AM +0530, Aneesh Kumar K.V wrote:
> Hi,
>
> I am getting this even with the latest patch queue. The test program is
> a modified fsstress with fallocate support.
>
> mpage_da_map_blocks block allocation failed for inode 377954 at logical
> offset 313 with max blocks 4 with error -28
> mpage_da_map_blocks block allocation failed for inode 336367 at logical
> offset 74 with max blocks 9 with error -28
> mpage_da_map_blocks block allocation failed for inode 345560 at logical
> offset 542 with max blocks 7 with error -28
> This should not happen.!! Data will be lost
> mpage_da_map_blocks block allocation failed for inode 355317 at logical
> offset 152 with max blocks 10 with error -28
> This should not happen.!! Data will be lost
> mpage_da_map_blocks block allocation failed for inode 395261 at logical
> offset 462 with max blocks 1 with error -28
> This should not happen.!! Data will be lost
> mpage_da_map_blocks block allocation failed for inode 323784 at logical
> offset 313 with max blocks 11 with error -28
> This should not happen.!! Data will be lost
>

With this patch i am not seeing error. It does the below

a) use ext4_claim_free_blocks that also update the free blocks count
b) Later after block allocation update the free blocks count if we
allocated less with non-delayed mode
c) Switch to non delay mode if we are low on free blocks.

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index dfe2d4f..5d0a676 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -1602,6 +1602,64 @@ ext4_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
return ret;
}

+int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
+ ext4_fsblk_t nblocks)
+{
+ int cpu;
+ s64 free_blocks;
+ ext4_fsblk_t root_blocks = 0;
+ struct percpu_counter *fbc = &sbi->s_freeblocks_counter;
+
+ free_blocks = percpu_counter_read(fbc);
+
+ if (!capable(CAP_SYS_RESOURCE) &&
+ sbi->s_resuid != current->fsuid &&
+ (sbi->s_resgid == 0 || !in_group_p(sbi->s_resgid)))
+ root_blocks = ext4_r_blocks_count(sbi->s_es);
+#ifdef CONFIG_SMP
+ /* Each CPU can accumulate FBC_BATCH blocks in their local
+ * counters. So we need to make sure we have free blocks more
+ * than FBC_BATCH * nr_cpu_ids. Also add a window of 4 times.
+ */
+ if (free_blocks - (nblocks + root_blocks) <
+ (4 * (FBC_BATCH * nr_cpu_ids))) {
+ /*
+ * We need to sum and claim under lock
+ * This is the slow patch which will be
+ * taken when we are very low on free blocks
+ */
+ spin_lock(&fbc->lock);
+ free_blocks = fbc->count;
+ for_each_online_cpu(cpu) {
+ s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
+ free_blocks += *pcount;
+ *pcount = 0;
+ }
+ fbc->count = free_blocks;
+ if (free_blocks <= root_blocks) {
+ /* we don't have free space */
+ spin_unlock(&fbc->lock);
+ return -ENOSPC;
+ }
+ if (free_blocks - root_blocks < nblocks) {
+ spin_unlock(&fbc->lock);
+ return -ENOSPC;
+ }
+ fbc->count -= nblocks;
+ spin_unlock(&fbc->lock);
+ return 0;
+ }
+#endif
+ if (free_blocks <= root_blocks)
+ /* we don't have free space */
+ return -ENOSPC;
+ if (free_blocks - root_blocks < nblocks)
+ return -ENOSPC;
+ /* reduce fs free blocks counter */
+ percpu_counter_sub(fbc, nblocks);
+ return 0;
+}
+
/**
* ext4_has_free_blocks()
* @sbi: in-core super block structure.
@@ -1624,9 +1682,15 @@ ext4_fsblk_t ext4_has_free_blocks(struct ext4_sb_info *sbi,
(sbi->s_resgid == 0 || !in_group_p(sbi->s_resgid)))
root_blocks = ext4_r_blocks_count(sbi->s_es);
#ifdef CONFIG_SMP
- if (free_blocks - root_blocks < FBC_BATCH)
+ /* Each CPU can accumulate FBC_BATCH blocks in their local
+ * counters. So we need to make sure we have free blocks more
+ * than FBC_BATCH * nr_cpu_ids. Also add a window of 4 times.
+ */
+ if (free_blocks - (nblocks + root_blocks) <
+ (4 * (FBC_BATCH * nr_cpu_ids))) {
free_blocks =
percpu_counter_sum_and_set(&sbi->s_freeblocks_counter);
+ }
#endif
if (free_blocks <= root_blocks)
/* we don't have free space */
@@ -1634,7 +1698,7 @@ ext4_fsblk_t ext4_has_free_blocks(struct ext4_sb_info *sbi,
if (free_blocks - root_blocks < nblocks)
return free_blocks - root_blocks;
return nblocks;
- }
+}

/**
@@ -1713,14 +1777,11 @@ ext4_fsblk_t ext4_old_new_blocks(handle_t *handle, struct inode *inode,
/*
* With delalloc we already reserved the blocks
*/
- *count = ext4_has_free_blocks(sbi, *count);
- }
- if (*count == 0) {
- *errp = -ENOSPC;
- return 0; /*return with ENOSPC error */
+ if (ext4_claim_free_blocks(sbi, *count)) {
+ *errp = -ENOSPC;
+ return 0; /*return with ENOSPC error */
+ }
}
- num = *count;
-
/*
* Check quota for allocation of this block.
*/
@@ -1915,9 +1976,13 @@ ext4_fsblk_t ext4_old_new_blocks(handle_t *handle, struct inode *inode,
le16_add_cpu(&gdp->bg_free_blocks_count, -num);
gdp->bg_checksum = ext4_group_desc_csum(sbi, group_no, gdp);
spin_unlock(sb_bgl_lock(sbi, group_no));
- if (!EXT4_I(inode)->i_delalloc_reserved_flag)
- percpu_counter_sub(&sbi->s_freeblocks_counter, num);
-
+ if (!EXT4_I(inode)->i_delalloc_reserved_flag && (*count != num)) {
+ /*
+ * we allocated less blocks than we
+ * claimed. Add the difference back.
+ */
+ percpu_counter_add(&sbi->s_freeblocks_counter, *count - num);
+ }
if (sbi->s_log_groups_per_flex) {
ext4_group_t flex_group = ext4_flex_group(sbi, group_no);
spin_lock(sb_bgl_lock(sbi, flex_group));
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 7f11b25..3738039 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1047,6 +1047,8 @@ extern ext4_fsblk_t ext4_new_blocks(handle_t *handle, struct inode *inode,
unsigned long *count, int *errp);
extern ext4_fsblk_t ext4_old_new_blocks(handle_t *handle, struct inode *inode,
ext4_fsblk_t goal, unsigned long *count, int *errp);
+extern int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
+ ext4_fsblk_t nblocks);
extern ext4_fsblk_t ext4_has_free_blocks(struct ext4_sb_info *sbi,
ext4_fsblk_t nblocks);
extern void ext4_free_blocks (handle_t *handle, struct inode *inode,
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index bf612a7..52902cc 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2815,6 +2815,7 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
path, iblock,
max_blocks);
if (ret <= 0) {
+ printk(KERN_CRIT "fallocate conversion failed %d\n", ret);
err = ret;
goto out2;
} else
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1c289c1..087abca 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1030,11 +1030,17 @@ static void ext4_da_update_reserve_space(struct inode *inode, int used)
BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
mdb_free = EXT4_I(inode)->i_reserved_meta_blocks - mdb;

- /* Account for allocated meta_blocks */
- mdb_free -= EXT4_I(inode)->i_allocated_meta_blocks;
+ if (mdb_free) {
+ /* Account for allocated meta_blocks */
+ mdb_free -= EXT4_I(inode)->i_allocated_meta_blocks;

- /* update fs free blocks counter for truncate case */
- percpu_counter_add(&sbi->s_freeblocks_counter, mdb_free);
+ /*
+ * We have reserved more blocks.
+ * Now free the extra blocks reserved
+ */
+ percpu_counter_add(&sbi->s_freeblocks_counter, mdb_free);
+ EXT4_I(inode)->i_allocated_meta_blocks = 0;
+ }

/* update per-inode reservations */
BUG_ON(used > EXT4_I(inode)->i_reserved_data_blocks);
@@ -1042,7 +1048,6 @@ static void ext4_da_update_reserve_space(struct inode *inode, int used)

BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
EXT4_I(inode)->i_reserved_meta_blocks = mdb;
- EXT4_I(inode)->i_allocated_meta_blocks = 0;
spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
}

@@ -1537,13 +1542,10 @@ static int ext4_da_reserve_space(struct inode *inode, int nrblocks)
md_needed = mdblocks - EXT4_I(inode)->i_reserved_meta_blocks;
total = md_needed + nrblocks;

- if (ext4_has_free_blocks(sbi, total) < total) {
+ if (ext4_claim_free_blocks(sbi, total)) {
spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
return -ENOSPC;
}
- /* reduce fs free blocks counter */
- percpu_counter_sub(&sbi->s_freeblocks_counter, total);
-
EXT4_I(inode)->i_reserved_data_blocks += nrblocks;
EXT4_I(inode)->i_reserved_meta_blocks = mdblocks;

@@ -2462,11 +2464,21 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
unsigned from, to;
struct inode *inode = mapping->host;
handle_t *handle;
+ s64 free_blocks;
+ struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);

index = pos >> PAGE_CACHE_SHIFT;
from = pos & (PAGE_CACHE_SIZE - 1);
to = from + len;

+ free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
+ if (free_blocks < (4 * (FBC_BATCH * nr_cpu_ids))) {
+ /* switch to non delalloc mode */
+ *fsdata = (void *)1;
+ return ext4_write_begin(file, mapping, pos,
+ len, flags, pagep, fsdata);
+ }
+ *fsdata = (void *)0;
retry:
/*
* With delayed allocation, we don't log the i_disksize update
@@ -2535,6 +2547,19 @@ static int ext4_da_write_end(struct file *file,
handle_t *handle = ext4_journal_current_handle();
loff_t new_i_size;
unsigned long start, end;
+ int low_free_blocks = (int)fsdata;
+
+ if (low_free_blocks) {
+ if (ext4_should_order_data(inode)) {
+ return ext4_ordered_write_end(file, mapping, pos,
+ len, copied, page, fsdata);
+ } else if (ext4_should_writeback_data(inode)) {
+ return ext4_writeback_write_end(file, mapping, pos,
+ len, copied, page, fsdata);
+ } else {
+ BUG();
+ }
+ }

start = pos & (PAGE_CACHE_SIZE - 1);
end = start + copied -1;
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 96319b2..7d94119 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2977,9 +2977,15 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
* at write_begin() time for delayed allocation
* do not double accounting
*/
- if (!(ac->ac_flags & EXT4_MB_DELALLOC_RESERVED))
- percpu_counter_sub(&sbi->s_freeblocks_counter,
- ac->ac_b_ex.fe_len);
+ if (!(ac->ac_flags & EXT4_MB_DELALLOC_RESERVED) &&
+ ac->ac_o_ex.fe_len != ac->ac_b_ex.fe_len) {
+ /*
+ * we allocated less blocks than we calimed
+ * Add the difference back
+ */
+ percpu_counter_add(&sbi->s_freeblocks_counter,
+ ac->ac_o_ex.fe_len -ac->ac_b_ex.fe_len);
+ }

if (sbi->s_log_groups_per_flex) {
ext4_group_t flex_group = ext4_flex_group(sbi,
@@ -4097,7 +4103,8 @@ static void ext4_mb_group_or_file(struct ext4_allocation_context *ac)
* per cpu locality group is to reduce the contention between block
* request from multiple CPUs.
*/
- ac->ac_lg = per_cpu_ptr(sbi->s_locality_groups, smp_processor_id());
+ ac->ac_lg = per_cpu_ptr(sbi->s_locality_groups, get_cpu());
+ put_cpu();

/* we're going to use group allocation */
ac->ac_flags |= EXT4_MB_HINT_GROUP_ALLOC;
@@ -4391,14 +4398,11 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
/*
* With delalloc we already reserved the blocks
*/
- ar->len = ext4_has_free_blocks(sbi, ar->len);
- }
-
- if (ar->len == 0) {
- *errp = -ENOSPC;
- return 0;
+ if (ext4_claim_free_blocks(sbi, ar->len)) {
+ *errp = -ENOSPC;
+ return 0;
+ }
}