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Message-ID: <20240904102244.ekzzhbwnzbtpeyjw@quack3>
Date: Wed, 4 Sep 2024 12:22:44 +0200
From: Jan Kara <jack@...e.cz>
To: Zhang Yi <yi.zhang@...weicloud.com>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, tytso@....edu,
adilger.kernel@...ger.ca, jack@...e.cz, ritesh.list@...il.com,
yi.zhang@...wei.com, chengzhihao1@...wei.com, yukuai3@...wei.com
Subject: Re: [PATCH v3 06/12] ext4: update delalloc data reserve spcae in
ext4_es_insert_extent()
On Tue 13-08-24 20:34:46, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
>
> 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@...wei.com>
I really like how simple this ended being! Feel free to add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/ext4/extents.c | 37 -------------------------------------
> fs/ext4/extents_status.c | 25 ++++++++++++++++++++++++-
> fs/ext4/indirect.c | 7 -------
> 3 files changed, 24 insertions(+), 45 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 671dacd7c873..db8f9d79477c 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -4357,43 +4357,6 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
> goto out;
> }
>
> - /*
> - * 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.
> - */
> - if (test_opt(inode->i_sb, DELALLOC) && allocated_clusters) {
> - if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) {
> - /*
> - * When allocating delayed allocated clusters, simply
> - * reduce the reserved cluster count and claim quota
> - */
> - ext4_da_update_reserve_space(inode, allocated_clusters,
> - 1);
> - } else {
> - ext4_lblk_t lblk, len;
> - unsigned int n;
> -
> - /*
> - * When allocating non-delayed allocated clusters
> - * (from fallocate, filemap, DIO, or clusters
> - * allocated when delalloc has been disabled by
> - * ext4_nonda_switch), reduce the reserved cluster
> - * count by the number of allocated clusters that
> - * have previously been delayed allocated. Quota
> - * has been claimed by ext4_mb_new_blocks() above,
> - * so release the quota reservations made for any
> - * previously delayed allocated clusters.
> - */
> - lblk = EXT4_LBLK_CMASK(sbi, map->m_lblk);
> - len = allocated_clusters << sbi->s_cluster_bits;
> - n = ext4_es_delayed_clu(inode, lblk, len);
> - if (n > 0)
> - ext4_da_update_reserve_space(inode, (int) n, 0);
> - }
> - }
> -
> /*
> * Cache the extent and update transaction to commit on fdatasync only
> * when it is _not_ an unwritten extent.
> 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 @@ void ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
> 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 @@ void ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
> __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;
>
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index d8ca7f64f952..7404f0935c90 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -652,13 +652,6 @@ int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
> ext4_update_inode_fsync_trans(handle, inode, 1);
> count = ar.len;
>
> - /*
> - * Update reserved blocks/metadata blocks after successful block
> - * allocation which had been deferred till now.
> - */
> - if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
> - ext4_da_update_reserve_space(inode, count, 1);
> -
> got_it:
> map->m_flags |= EXT4_MAP_MAPPED;
> map->m_pblk = le32_to_cpu(chain[depth-1].key);
> --
> 2.39.2
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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