ext4: delayed allocation ENOSPC handling

This patch does block reservation for delayed
allocation, to avoid ENOSPC later at page flush time.

Blocks(data and metadata) are reserved at da_write_begin()
time, the freeblocks counter is updated by then, and the number of
reserved blocks is store in per inode counter.
        
At the writepage time, the unused reserved meta blocks are returned
back. At unlink/truncate time, reserved blocks are properly released.

Updated fix from  Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
to fix the oldallocator block reservation accounting with delalloc, added
lock to guard the counters and also fix the reservation for meta blocks.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 32 insertions, 17 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 6369bacf0dcb..495ab21b9832 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -1701,7 +1701,12 @@ ext4_fsblk_t ext4_old_new_blocks(handle_t *handle, struct inode *inode,
         }
 
         sbi = EXT4_SB(sb);
-        *count = ext4_has_free_blocks(sbi, *count);
+        if (!EXT4_I(inode)->i_delalloc_reserved_flag) {
+                /*
+                 * 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 */
@@ -1902,7 +1907,8 @@ allocated:
         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));
-        percpu_counter_sub(&sbi->s_freeblocks_counter, num);
+        if (!EXT4_I(inode)->i_delalloc_reserved_flag)
+                percpu_counter_sub(&sbi->s_freeblocks_counter, num);
 
         if (sbi->s_log_groups_per_flex) {
                 ext4_group_t flex_group = ext4_flex_group(sbi, group_no);
@@ -1976,40 +1982,49 @@ static ext4_fsblk_t do_blk_alloc(handle_t *handle, struct inode *inode,
 }
 
 /*
- * ext4_new_meta_block() -- allocate block for meta data (indexing) blocks
+ * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
  *
  * @handle:             handle to this transaction
  * @inode:              file inode
  * @goal:               given target block(filesystem wide)
+ * @count:              total number of blocks need
  * @errp:               error code
  *
- * Return allocated block number on success
+ * Return 1st allocated block numberon success, *count stores total account
+ * error stores in errp pointer
  */
-ext4_fsblk_t ext4_new_meta_block(handle_t *handle, struct inode *inode,
-                ext4_fsblk_t goal, int *errp)
+ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
+                ext4_fsblk_t goal, unsigned long *count, int *errp)
 {
-        unsigned long count = 1;
-        return do_blk_alloc(handle, inode, 0, goal,
-                        &count, errp, EXT4_META_BLOCK);
+        ext4_fsblk_t ret;
+        ret = do_blk_alloc(handle, inode, 0, goal,
+                                count, errp, EXT4_META_BLOCK);
+        /*
+         * Account for the allocated meta blocks
+         */
+        if (!(*errp)) {
+                spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
+                EXT4_I(inode)->i_allocated_meta_blocks += *count;
+                spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
+        }
+        return ret;
 }
 
 /*
- * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
+ * ext4_new_meta_block() -- allocate block for meta data (indexing) blocks
  *
  * @handle:             handle to this transaction
  * @inode:              file inode
  * @goal:               given target block(filesystem wide)
- * @count:              total number of blocks need
  * @errp:               error code
  *
- * Return 1st allocated block numberon success, *count stores total account
- * error stores in errp pointer
+ * Return allocated block number on success
  */
-ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
-                ext4_fsblk_t goal, unsigned long *count, int *errp)
+ext4_fsblk_t ext4_new_meta_block(handle_t *handle, struct inode *inode,
+                ext4_fsblk_t goal, int *errp)
 {
-        return do_blk_alloc(handle, inode, 0, goal,
-                        count, errp, EXT4_META_BLOCK);
+        unsigned long count = 1;
+        return ext4_new_meta_blocks(handle, inode, goal, &count, errp);
 }
 
 /*