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/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--;