Re: [PATCH v2 5/9] ext4: make ext4_es_insert_delayed_block() insert multi-blocks

Jan Kara
2024-04-29T09:16:40Z

On Wed 10-04-24 11:41:59, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@huawei.com>
>
> Rename ext4_es_insert_delayed_block() to ext4_es_insert_delayed_extent()
> and pass length parameter to make it insert multi delalloc blocks once a
> time. For the case of bigalloc, expand the allocated parameter to
> lclu_allocated and end_allocated. lclu_allocated indicates the allocate
> state of the cluster which containing the lblk, end_allocated represents
> the end, and the middle clusters must be unallocated.
>
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>

Looks mostly good, just one comment below:

> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index 4a00e2f019d9..2320b0d71001 100644
> --- a/fs/ext4/extents_status.c
> +++ b/fs/ext4/extents_status.c
> @@ -2052,34 +2052,42 @@ bool ext4_is_pending(struct inode *inode, ext4_lblk_t lblk)
> }
>
> /*
> - * ext4_es_insert_delayed_block - adds a delayed block to the extents status
> - * tree, adding a pending reservation where
> - * needed
> + * ext4_es_insert_delayed_extent - adds some delayed blocks to the extents
> + * status tree, adding a pending reservation
> + * where needed
> *
> * @inode - file containing the newly added block
> - * @lblk - logical block to be added
> - * @allocated - indicates whether a physical cluster has been allocated for
> - * the logical cluster that contains the block
> + * @lblk - start logical block to be added
> + * @len - length of blocks to be added
> + * @lclu_allocated/end_allocated - indicates whether a physical cluster has
> + * been allocated for the logical cluster
> + * that contains the block
^^^^ "start / end
block" to make it clearer...

> -void ext4_es_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk,
> - bool allocated)
> +void ext4_es_insert_delayed_extent(struct inode *inode, ext4_lblk_t lblk,
> + ext4_lblk_t len, bool lclu_allocated,
> + bool end_allocated)
> {
> struct extent_status newes;
> + ext4_lblk_t end = lblk + len - 1;
> int err1 = 0, err2 = 0, err3 = 0;
> struct extent_status *es1 = NULL;
> struct extent_status *es2 = NULL;
> - struct pending_reservation *pr = NULL;
> + struct pending_reservation *pr1 = NULL;
> + struct pending_reservation *pr2 = NULL;
>
> if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
> return;
>
> - es_debug("add [%u/1) delayed to extent status tree of inode %lu\n",
> - lblk, inode->i_ino);
> + es_debug("add [%u/%u) delayed to extent status tree of inode %lu\n",
> + lblk, len, inode->i_ino);
> + if (!len)
> + return;
>
> newes.es_lblk = lblk;
> - newes.es_len = 1;
> + newes.es_len = len;
> ext4_es_store_pblock_status(&newes, ~0, EXTENT_STATUS_DELAYED);
> - trace_ext4_es_insert_delayed_block(inode, &newes, allocated);
> + trace_ext4_es_insert_delayed_extent(inode, &newes, lclu_allocated,
> + end_allocated);
>
> ext4_es_insert_extent_check(inode, &newes);
>
> @@ -2088,11 +2096,15 @@ void ext4_es_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk,
> es1 = __es_alloc_extent(true);
> if ((err1 || err2) && !es2)
> es2 = __es_alloc_extent(true);
> - if ((err1 || err2 || err3) && allocated && !pr)
> - pr = __alloc_pending(true);
> + if (err1 || err2 || err3) {
> + if (lclu_allocated && !pr1)
> + pr1 = __alloc_pending(true);
> + if (end_allocated && !pr2)
> + pr2 = __alloc_pending(true);
> + }
> write_lock(&EXT4_I(inode)->i_es_lock);
>
> - err1 = __es_remove_extent(inode, lblk, lblk, NULL, es1);
> + err1 = __es_remove_extent(inode, lblk, end, NULL, es1);
> if (err1 != 0)
> goto error;
> /* Free preallocated extent if it didn't get used. */
> @@ -2112,13 +2124,22 @@ void ext4_es_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk,
> es2 = NULL;
> }
>
> - if (allocated) {
> - err3 = __insert_pending(inode, lblk, &pr);
> + if (lclu_allocated) {
> + err3 = __insert_pending(inode, lblk, &pr1);
> if (err3 != 0)
> goto error;
> - if (pr) {
> - __free_pending(pr);
> - pr = NULL;
> + if (pr1) {
> + __free_pending(pr1);
> + pr1 = NULL;
> + }
> + }
> + if (end_allocated) {

So there's one unclear thing here: What if 'lblk' and 'end' are in the same
cluster? We don't want two pending reservation structures for the cluster.
__insert_pending() already handles this gracefully but perhaps we don't
need to allocate 'pr2' in that case and call __insert_pending() at all? I
think it could be easily handled by something like:

if (EXT4_B2C(lblk) == EXT4_B2C(end))
end_allocated = false;

at appropriate place in ext4_es_insert_delayed_extent().

Otherwise the patch looks good.

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR