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Message-ID: <Z2KhPcxh9ESbD5l5@li-bb2b2a4c-3307-11b2-a85c-8fa5c3a69313.ibm.com>
Date: Wed, 18 Dec 2024 15:47:33 +0530
From: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
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, yi.zhang@...wei.com, chengzhihao1@...wei.com,
yukuai3@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH v4 04/10] ext4: refactor ext4_punch_hole()
On Mon, Dec 16, 2024 at 09:39:09AM +0800, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
>
> The current implementation of ext4_punch_hole() contains complex
> position calculations and stale error tags. To improve the code's
> clarity and maintainability, it is essential to clean up the code and
> improve its readability, this can be achieved by: a) simplifying and
> renaming variables; b) eliminating unnecessary position calculations;
> c) writing back all data in data=journal mode, and drop page cache from
> the original offset to the end, rather than using aligned blocks,
> d) renaming the stale error tags.
>
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
> ---
> fs/ext4/ext4.h | 2 +
> fs/ext4/inode.c | 119 +++++++++++++++++++++---------------------------
> 2 files changed, 55 insertions(+), 66 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 8843929b46ce..8be06d5f5b43 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -367,6 +367,8 @@ struct ext4_io_submit {
> #define EXT4_MAX_BLOCKS(size, offset, blkbits) \
> ((EXT4_BLOCK_ALIGN(size + offset, blkbits) >> blkbits) - (offset >> \
> blkbits))
> +#define EXT4_B_TO_LBLK(inode, offset) \
> + (round_up((offset), i_blocksize(inode)) >> (inode)->i_blkbits)
>
> /* Translate a block number to a cluster number */
> #define EXT4_B2C(sbi, blk) ((blk) >> (sbi)->s_cluster_bits)
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index a5ba2b71d508..7720d3700b27 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4008,13 +4008,13 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
> {
> struct inode *inode = file_inode(file);
> struct super_block *sb = inode->i_sb;
> - ext4_lblk_t first_block, stop_block;
> + ext4_lblk_t start_lblk, end_lblk;
> struct address_space *mapping = inode->i_mapping;
> - loff_t first_block_offset, last_block_offset, max_length;
> - struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> + loff_t max_end = EXT4_SB(sb)->s_bitmap_maxbytes - sb->s_blocksize;
> + loff_t end = offset + length;
> handle_t *handle;
> unsigned int credits;
> - int ret = 0, ret2 = 0;
> + int ret = 0;
>
> trace_ext4_punch_hole(inode, offset, length, 0);
>
> @@ -4022,36 +4022,27 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
>
> /* No need to punch hole beyond i_size */
> if (offset >= inode->i_size)
> - goto out_mutex;
> + goto out;
>
> /*
> - * If the hole extends beyond i_size, set the hole
> - * to end after the page that contains i_size
> + * If the hole extends beyond i_size, set the hole to end after
> + * the page that contains i_size, and also make sure that the hole
> + * within one block before last range.
> */
> - if (offset + length > inode->i_size) {
> - length = inode->i_size +
> - PAGE_SIZE - (inode->i_size & (PAGE_SIZE - 1)) -
> - offset;
> - }
> + if (end > inode->i_size)
> + end = round_up(inode->i_size, PAGE_SIZE);
> + if (end > max_end)
> + end = max_end;
> + length = end - offset;
>
> /*
> - * For punch hole the length + offset needs to be within one block
> - * before last range. Adjust the length if it goes beyond that limit.
> + * Attach jinode to inode for jbd2 if we do any zeroing of partial
> + * block.
> */
> - max_length = sbi->s_bitmap_maxbytes - inode->i_sb->s_blocksize;
> - if (offset + length > max_length)
> - length = max_length - offset;
> -
> - if (offset & (sb->s_blocksize - 1) ||
> - (offset + length) & (sb->s_blocksize - 1)) {
> - /*
> - * Attach jinode to inode for jbd2 if we do any zeroing of
> - * partial block
> - */
> + if (!IS_ALIGNED(offset | end, sb->s_blocksize)) {
> ret = ext4_inode_attach_jinode(inode);
> if (ret < 0)
> - goto out_mutex;
> -
> + goto out;
> }
>
> /* Wait all existing dio workers, newcomers will block on i_rwsem */
> @@ -4059,7 +4050,7 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
>
> ret = file_modified(file);
> if (ret)
> - goto out_mutex;
> + goto out;
>
> /*
> * Prevent page faults from reinstantiating pages we have released from
> @@ -4069,22 +4060,16 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
>
> ret = ext4_break_layouts(inode);
> if (ret)
> - goto out_dio;
> + goto out_invalidate_lock;
>
> - first_block_offset = round_up(offset, sb->s_blocksize);
> - last_block_offset = round_down((offset + length), sb->s_blocksize) - 1;
> + ret = ext4_update_disksize_before_punch(inode, offset, length);
Hey Zhang,
The changes look good to me, just one question, why are we doing
disksize update unconditionally now and not only when the range
spans a complete block or more.
(Same question for the next patch refactoring ext4_zero_range())
Regards,
ojaswin
> + if (ret)
> + goto out_invalidate_lock;
>
> /* Now release the pages and zero block aligned part of pages*/
> - if (last_block_offset > first_block_offset) {
> - ret = ext4_update_disksize_before_punch(inode, offset, length);
> - if (ret)
> - goto out_dio;
> -
> - ret = ext4_truncate_page_cache_block_range(inode,
> - first_block_offset, last_block_offset + 1);
> - if (ret)
> - goto out_dio;
> - }
> + ret = ext4_truncate_page_cache_block_range(inode, offset, end);
> + if (ret)
> + goto out_invalidate_lock;
>
> if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
> credits = ext4_writepage_trans_blocks(inode);
> @@ -4094,52 +4079,54 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length)
> if (IS_ERR(handle)) {
> ret = PTR_ERR(handle);
> ext4_std_error(sb, ret);
> - goto out_dio;
> + goto out_invalidate_lock;
> }
>
> - ret = ext4_zero_partial_blocks(handle, inode, offset,
> - length);
> + ret = ext4_zero_partial_blocks(handle, inode, offset, length);
> if (ret)
> - goto out_stop;
> -
> - first_block = (offset + sb->s_blocksize - 1) >>
> - EXT4_BLOCK_SIZE_BITS(sb);
> - stop_block = (offset + length) >> EXT4_BLOCK_SIZE_BITS(sb);
> + goto out_handle;
>
> /* If there are blocks to remove, do it */
> - if (stop_block > first_block) {
> - ext4_lblk_t hole_len = stop_block - first_block;
> + start_lblk = EXT4_B_TO_LBLK(inode, offset);
> + end_lblk = end >> inode->i_blkbits;
> +
> + if (end_lblk > start_lblk) {
> + ext4_lblk_t hole_len = end_lblk - start_lblk;
>
> down_write(&EXT4_I(inode)->i_data_sem);
> ext4_discard_preallocations(inode);
>
> - ext4_es_remove_extent(inode, first_block, hole_len);
> + ext4_es_remove_extent(inode, start_lblk, hole_len);
>
> if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
> - ret = ext4_ext_remove_space(inode, first_block,
> - stop_block - 1);
> + ret = ext4_ext_remove_space(inode, start_lblk,
> + end_lblk - 1);
> else
> - ret = ext4_ind_remove_space(handle, inode, first_block,
> - stop_block);
> + ret = ext4_ind_remove_space(handle, inode, start_lblk,
> + end_lblk);
> + if (ret) {
> + up_write(&EXT4_I(inode)->i_data_sem);
> + goto out_handle;
> + }
>
> - ext4_es_insert_extent(inode, first_block, hole_len, ~0,
> + ext4_es_insert_extent(inode, start_lblk, hole_len, ~0,
> EXTENT_STATUS_HOLE, 0);
> up_write(&EXT4_I(inode)->i_data_sem);
> }
> - ext4_fc_track_range(handle, inode, first_block, stop_block);
> + ext4_fc_track_range(handle, inode, start_lblk, end_lblk);
> +
> + ret = ext4_mark_inode_dirty(handle, inode);
> + if (unlikely(ret))
> + goto out_handle;
> +
> + ext4_update_inode_fsync_trans(handle, inode, 1);
> if (IS_SYNC(inode))
> ext4_handle_sync(handle);
> -
> - ret2 = ext4_mark_inode_dirty(handle, inode);
> - if (unlikely(ret2))
> - ret = ret2;
> - if (ret >= 0)
> - ext4_update_inode_fsync_trans(handle, inode, 1);
> -out_stop:
> +out_handle:
> ext4_journal_stop(handle);
> -out_dio:
> +out_invalidate_lock:
> filemap_invalidate_unlock(mapping);
> -out_mutex:
> +out:
> inode_unlock(inode);
> return ret;
> }
> --
> 2.46.1
>
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