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Message-ID: <20240920162422.sfoefd3bng6wwhir@quack3>
Date: Fri, 20 Sep 2024 18:24:22 +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 v2 04/10] ext4: refactor ext4_zero_range()
On Wed 04-09-24 14:29:19, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
>
> Current ext4_zero_range() is full of complex position calculation and
> stale error out tags. In order to clean up the code and make things
> clear, refactor it by a) simplify and rename variables, b) remove some
> unnecessary position calculations, always write back dirty data and
> drop cache from offset to end, instead of only write back aligned
> blocks, c) rename the stale out_mutex tag.
>
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
Looks good to me. Feel free to add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/ext4/extents.c | 96 ++++++++++++++++++-----------------------------
> 1 file changed, 37 insertions(+), 59 deletions(-)
>
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index d9fccf2970e9..2fb0c2e303c7 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -4540,40 +4540,15 @@ static long ext4_zero_range(struct file *file, loff_t offset,
> struct inode *inode = file_inode(file);
> struct address_space *mapping = file->f_mapping;
> handle_t *handle = NULL;
> - unsigned int max_blocks;
> loff_t new_size = 0;
> - int ret = 0;
> - int flags;
> - int credits;
> - int partial_begin, partial_end;
> - loff_t start, end;
> - ext4_lblk_t lblk;
> + loff_t end = offset + len;
> + ext4_lblk_t start_lblk, end_lblk;
> + unsigned int blocksize = i_blocksize(inode);
> unsigned int blkbits = inode->i_blkbits;
> + int ret, flags, credits;
>
> trace_ext4_zero_range(inode, offset, len, mode);
>
> - /*
> - * Round up offset. This is not fallocate, we need to zero out
> - * blocks, so convert interior block aligned part of the range to
> - * unwritten and possibly manually zero out unaligned parts of the
> - * range. Here, start and partial_begin are inclusive, end and
> - * partial_end are exclusive.
> - */
> - start = round_up(offset, 1 << blkbits);
> - end = round_down((offset + len), 1 << blkbits);
> -
> - if (start < offset || end > offset + len)
> - return -EINVAL;
> - partial_begin = offset & ((1 << blkbits) - 1);
> - partial_end = (offset + len) & ((1 << blkbits) - 1);
> -
> - lblk = start >> blkbits;
> - max_blocks = (end >> blkbits);
> - if (max_blocks < lblk)
> - max_blocks = 0;
> - else
> - max_blocks -= lblk;
> -
> inode_lock(inode);
>
> /*
> @@ -4581,26 +4556,23 @@ static long ext4_zero_range(struct file *file, loff_t offset,
> */
> if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
> ret = -EOPNOTSUPP;
> - goto out_mutex;
> + goto out;
> }
>
> if (!(mode & FALLOC_FL_KEEP_SIZE) &&
> - (offset + len > inode->i_size ||
> - offset + len > EXT4_I(inode)->i_disksize)) {
> - new_size = offset + len;
> + (end > inode->i_size || end > EXT4_I(inode)->i_disksize)) {
> + new_size = end;
> ret = inode_newsize_ok(inode, new_size);
> if (ret)
> - goto out_mutex;
> + goto out;
> }
>
> - flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT;
> -
> /* Wait all existing dio workers, newcomers will block on i_rwsem */
> inode_dio_wait(inode);
>
> ret = file_modified(file);
> if (ret)
> - goto out_mutex;
> + goto out;
>
> /*
> * Prevent page faults from reinstantiating pages we have released
> @@ -4616,36 +4588,40 @@ static long ext4_zero_range(struct file *file, loff_t offset,
> * Write data that will be zeroed to preserve them when successfully
> * discarding page cache below but fail to convert extents.
> */
> - ret = filemap_write_and_wait_range(mapping, start, end - 1);
> + ret = filemap_write_and_wait_range(mapping, offset, end - 1);
> if (ret)
> goto out_invalidate_lock;
>
> + /* Now release the pages and zero block aligned part of pages */
> + truncate_pagecache_range(inode, offset, end - 1);
> +
> + flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT;
> /* Preallocate the range including the unaligned edges */
> - if (partial_begin || partial_end) {
> - ret = ext4_alloc_file_blocks(file,
> - round_down(offset, 1 << blkbits) >> blkbits,
> - (round_up((offset + len), 1 << blkbits) -
> - round_down(offset, 1 << blkbits)) >> blkbits,
> - new_size, flags);
> + if (offset & (blocksize - 1) || end & (blocksize - 1)) {
> + ext4_lblk_t alloc_lblk = offset >> blkbits;
> + ext4_lblk_t len_lblk = EXT4_MAX_BLOCKS(len, offset, blkbits);
> +
> + ret = ext4_alloc_file_blocks(file, alloc_lblk, len_lblk,
> + new_size, flags);
> if (ret)
> goto out_invalidate_lock;
>
> }
>
> /* Zero range excluding the unaligned edges */
> - if (max_blocks > 0) {
> - flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN |
> - EXT4_EX_NOCACHE);
> -
> - /* Now release the pages and zero block aligned part of pages */
> - truncate_pagecache_range(inode, start, end - 1);
> -
> - ret = ext4_alloc_file_blocks(file, lblk, max_blocks, new_size,
> - flags);
> + start_lblk = round_up(offset, blocksize) >> blkbits;
> + end_lblk = end >> blkbits;
> + if (end_lblk > start_lblk) {
> + ext4_lblk_t zero_blks = end_lblk - start_lblk;
> +
> + flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN | EXT4_EX_NOCACHE);
> + ret = ext4_alloc_file_blocks(file, start_lblk, zero_blks,
> + new_size, flags);
> if (ret)
> goto out_invalidate_lock;
> }
> - if (!partial_begin && !partial_end)
> + /* Finish zeroing out if it doesn't contain partial block */
> + if (!(offset & (blocksize - 1)) && !(end & (blocksize - 1)))
> goto out_invalidate_lock;
>
> /*
> @@ -4662,16 +4638,18 @@ static long ext4_zero_range(struct file *file, loff_t offset,
> goto out_invalidate_lock;
> }
>
> + /* Zero out partial block at the edges of the range */
> + ret = ext4_zero_partial_blocks(handle, inode, offset, len);
> + if (ret)
> + goto out_handle;
> +
> if (new_size)
> ext4_update_inode_size(inode, new_size);
> ret = ext4_mark_inode_dirty(handle, inode);
> if (unlikely(ret))
> goto out_handle;
> - /* Zero out partial block at the edges of the range */
> - ret = ext4_zero_partial_blocks(handle, inode, offset, len);
> - if (ret >= 0)
> - ext4_update_inode_fsync_trans(handle, inode, 1);
>
> + ext4_update_inode_fsync_trans(handle, inode, 1);
> if (file->f_flags & O_SYNC)
> ext4_handle_sync(handle);
>
> @@ -4679,7 +4657,7 @@ static long ext4_zero_range(struct file *file, loff_t offset,
> ext4_journal_stop(handle);
> out_invalidate_lock:
> filemap_invalidate_unlock(mapping);
> -out_mutex:
> +out:
> inode_unlock(inode);
> return ret;
> }
> --
> 2.39.2
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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