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Date: Mon, 29 Apr 2024 20:09:46 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: Jan Kara <jack@...e.cz>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, tytso@....edu,
adilger.kernel@...ger.ca, yi.zhang@...wei.com, chengzhihao1@...wei.com,
yukuai3@...wei.com
Subject: Re: [PATCH v2 5/9] ext4: make ext4_es_insert_delayed_block() insert
multi-blocks
On 2024/4/29 17:16, Jan Kara wrote:
> On Wed 10-04-24 11:41:59, Zhang Yi wrote:
>> From: Zhang Yi <yi.zhang@...wei.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@...wei.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().
>
I've done the check "EXT4_B2C(lblk) == EXT4_B2C(end)" in the caller
ext4_insert_delayed_blocks() in patch 8, becasue there is no need to check
the allocation state if they are in the same cluster, so it could make sure
that end_allocated is always false when 'lblk' and 'end' are in the same
cluster. So I suppose check and set it here again maybe redundant, how about
add a wanging here in ext4_es_insert_delayed_extent(), like:
WARN_ON_ONCE((EXT4_B2C(sbi, lblk) == EXT4_B2C(sbi, end)) &&
end_allocated);
and modify the 'lclu_allocated/end_allocated' parameter comments, note that
end_allocated should always be set to false if the extent is in one cluster.
Is it fine?
Thanks,
Yi.
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