ext4: Make sure all the block allocation paths reserve blocks
With delayed allocation we need to make sure block are reserved before
we attempt to allocate them. Otherwise we get block allocation failure
(ENOSPC) during writepages which cannot be handled. This would mean
silent data loss (We do a printk stating data will be lost). This patch
updates the DIO and fallocate code path to do block reservation before
block allocation. This is needed to make sure parallel DIO and fallocate
request doesn't take block out of delayed reserve space.
When free blocks count go below a threshold we switch to a slow patch
which looks at other CPU's accumulated percpu counter values.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 58005c0..1707850 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -1602,6 +1602,32 @@
return ret;
}
+int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
+ ext4_fsblk_t nblocks)
+{
+ 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);
+
+ if (free_blocks - (nblocks + root_blocks) < EXT4_FREEBLOCKS_WATERMARK)
+ free_blocks = percpu_counter_sum(&sbi->s_freeblocks_counter);
+
+ if (free_blocks < (root_blocks + nblocks))
+ /* we don't have free space */
+ return -ENOSPC;
+
+ /* reduce fs free blocks counter */
+ percpu_counter_sub(fbc, nblocks);
+ return 0;
+}
+
/**
* ext4_has_free_blocks()
* @sbi: in-core super block structure.
@@ -1623,18 +1649,17 @@
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
- if (free_blocks - root_blocks < FBC_BATCH)
- free_blocks =
- percpu_counter_sum(&sbi->s_freeblocks_counter);
-#endif
+
+ if (free_blocks - (nblocks + root_blocks) < EXT4_FREEBLOCKS_WATERMARK)
+ free_blocks = percpu_counter_sum_positive(&sbi->s_freeblocks_counter);
+
if (free_blocks <= root_blocks)
/* we don't have free space */
return 0;
if (free_blocks - root_blocks < nblocks)
return free_blocks - root_blocks;
return nblocks;
- }
+}
/**
@@ -1713,14 +1738,11 @@
/*
* With delalloc we already reserved the blocks
*/
- *count = ext4_has_free_blocks(sbi, *count);
+ if (ext4_claim_free_blocks(sbi, *count)) {
+ *errp = -ENOSPC;
+ return 0; /*return with ENOSPC error */
+ }
}
- if (*count == 0) {
- *errp = -ENOSPC;
- return 0; /*return with ENOSPC error */
- }
- num = *count;
-
/*
* Check quota for allocation of this block.
*/
@@ -1915,9 +1937,13 @@
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 8c70131..0154c2d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -983,6 +983,8 @@
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,
@@ -1207,6 +1209,17 @@
__ext4_std_error((sb), __func__, (errno)); \
} while (0)
+#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.
+ */
+#define EXT4_FREEBLOCKS_WATERMARK (4 * (FBC_BATCH * nr_cpu_ids))
+#else
+#define EXT4_FREEBLOCKS_WATERMARK 0
+#endif
+
+
/*
* Inodes and files operations
*/
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b6fa0c4..b778d5a 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1537,13 +1537,10 @@
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;
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 0db2ccf..2c10b50 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2975,9 +2975,15 @@
* 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,
@@ -4389,14 +4395,11 @@
/*
* With delalloc we already reserved the blocks
*/
- ar->len = ext4_has_free_blocks(sbi, ar->len);
+ if (ext4_claim_free_blocks(sbi, ar->len)) {
+ *errp = -ENOSPC;
+ return 0;
+ }
}
-
- if (ar->len == 0) {
- *errp = -ENOSPC;
- return 0;
- }
-
while (ar->len && DQUOT_ALLOC_BLOCK(ar->inode, ar->len)) {
ar->flags |= EXT4_MB_HINT_NOPREALLOC;
ar->len--;