ext4: update delalloc data reserve spcae in ext4_es_insert_extent()

Now that we update data reserved space for delalloc after allocating
new blocks in ext4_{ind|ext}_map_blocks(), and if bigalloc feature is
enabled, we also need to query the extents_status tree to calculate the
exact reserved clusters. This is complicated now and it appears that
it's better to do this job in ext4_es_insert_extent(), because
__es_remove_extent() have already count delalloc blocks when removing
delalloc extents and __revise_pending() return new adding pending count,
we could update the reserved blocks easily in ext4_es_insert_extent().

We direct reduce the reserved cluster count when replacing a delalloc
extent. However, thers are two special cases need to concern about the
quota claiming when doing direct block allocation (e.g. from fallocate).

A),
fallocate a range that covers a delalloc extent but start with
non-delayed allocated blocks, e.g. a hole.

  hhhhhhh+ddddddd+ddddddd
  ^^^^^^^^^^^^^^^^^^^^^^^  fallocate this range

Current ext4_map_blocks() can't always trim the extent since it may
release i_data_sem before calling ext4_map_create_blocks() and raced by
another delayed allocation. Hence the EXT4_GET_BLOCKS_DELALLOC_RESERVE
may not set even when we are replacing a delalloc extent, without this
flag set, the quota has already been claimed by ext4_mb_new_blocks(), so
we should release the quota reservations instead of claim them again.

B),
bigalloc feature is enabled, fallocate a range that contains non-delayed
allocated blocks.

  |<         one cluster       >|
  hhhhhhh+hhhhhhh+hhhhhhh+ddddddd
  ^^^^^^^  fallocate this range

This case is similar to above case, the EXT4_GET_BLOCKS_DELALLOC_RESERVE
flag is also not set.

Hence we should release the quota reservations if we replace a delalloc
extent but without EXT4_GET_BLOCKS_DELALLOC_RESERVE set.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20240813123452.2824659-7-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 24 insertions, 1 deletions

diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 0580bc4bc762..41adf0d69959 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -853,6 +853,7 @@ void ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
 	struct extent_status newes;
 	ext4_lblk_t end = lblk + len - 1;
 	int err1 = 0, err2 = 0, err3 = 0;
+	int resv_used = 0, pending = 0;
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 	struct extent_status *es1 = NULL;
 	struct extent_status *es2 = NULL;
@@ -891,7 +892,7 @@ retry:
 		pr = __alloc_pending(true);
 	write_lock(&EXT4_I(inode)->i_es_lock);
 
-	err1 = __es_remove_extent(inode, lblk, end, NULL, es1);
+	err1 = __es_remove_extent(inode, lblk, end, &resv_used, es1);
 	if (err1 != 0)
 		goto error;
 	/* Free preallocated extent if it didn't get used. */
@@ -921,9 +922,31 @@ retry:
 			__free_pending(pr);
 			pr = NULL;
 		}
+		pending = err3;
 	}
 error:
 	write_unlock(&EXT4_I(inode)->i_es_lock);
+	/*
+	 * Reduce the reserved cluster count to reflect successful deferred
+	 * allocation of delayed allocated clusters or direct allocation of
+	 * clusters discovered to be delayed allocated.  Once allocated, a
+	 * cluster is not included in the reserved count.
+	 *
+	 * When direct allocating (from fallocate, filemap, DIO, or clusters
+	 * allocated when delalloc has been disabled by ext4_nonda_switch())
+	 * an extent either 1) contains delayed blocks but start with
+	 * non-delayed allocated blocks (e.g. hole) or 2) contains non-delayed
+	 * allocated blocks which belong to delayed allocated clusters when
+	 * bigalloc feature is enabled, quota has already been claimed by
+	 * ext4_mb_new_blocks(), so release the quota reservations made for
+	 * any previously delayed allocated clusters instead of claim them
+	 * again.
+	 */
+	resv_used += pending;
+	if (resv_used)
+		ext4_da_update_reserve_space(inode, resv_used,
+				flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE);
+
 	if (err1 || err2 || err3 < 0)
 		goto retry;