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Date: Fri, 13 Aug 2021 15:00:55 +0200
From: Jan Kara <jack@...e.cz>
To: Zhang Yi <yi.zhang@...wei.com>
Cc: linux-ext4@...r.kernel.org, tytso@....edu,
adilger.kernel@...ger.ca, jack@...e.cz, yukuai3@...wei.com
Subject: Re: [PATCH 2/3] ext4: remove an unnecessary if statement in
__ext4_get_inode_loc()
On Tue 10-08-21 22:27:21, Zhang Yi wrote:
> The "if (!buffer_uptodate(bh))" hunk covered almost the whole code after
> getting buffer in __ext4_get_inode_loc() which seems unnecessary, remove
> it and switch to check ext4_buffer_uptodate(), it simplify code and make
> it more readable.
>
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/ext4/inode.c | 162 +++++++++++++++++++++++-------------------------
> 1 file changed, 78 insertions(+), 84 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index eb2526a35254..eae1b2d0b550 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4330,99 +4330,93 @@ static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino,
> bh = sb_getblk(sb, block);
> if (unlikely(!bh))
> return -ENOMEM;
> - if (!buffer_uptodate(bh)) {
> - lock_buffer(bh);
> -
> - if (ext4_buffer_uptodate(bh)) {
> - /* someone brought it uptodate while we waited */
> - unlock_buffer(bh);
> - goto has_buffer;
> - }
> + if (ext4_buffer_uptodate(bh))
> + goto has_buffer;
>
> - /*
> - * If we have all information of the inode in memory and this
> - * is the only valid inode in the block, we need not read the
> - * block.
> - */
> - if (in_mem) {
> - struct buffer_head *bitmap_bh;
> - int i, start;
> + lock_buffer(bh);
> + /*
> + * If we have all information of the inode in memory and this
> + * is the only valid inode in the block, we need not read the
> + * block.
> + */
> + if (in_mem) {
> + struct buffer_head *bitmap_bh;
> + int i, start;
>
> - start = inode_offset & ~(inodes_per_block - 1);
> + start = inode_offset & ~(inodes_per_block - 1);
>
> - /* Is the inode bitmap in cache? */
> - bitmap_bh = sb_getblk(sb, ext4_inode_bitmap(sb, gdp));
> - if (unlikely(!bitmap_bh))
> - goto make_io;
> + /* Is the inode bitmap in cache? */
> + bitmap_bh = sb_getblk(sb, ext4_inode_bitmap(sb, gdp));
> + if (unlikely(!bitmap_bh))
> + goto make_io;
>
> - /*
> - * If the inode bitmap isn't in cache then the
> - * optimisation may end up performing two reads instead
> - * of one, so skip it.
> - */
> - if (!buffer_uptodate(bitmap_bh)) {
> - brelse(bitmap_bh);
> - goto make_io;
> - }
> - for (i = start; i < start + inodes_per_block; i++) {
> - if (i == inode_offset)
> - continue;
> - if (ext4_test_bit(i, bitmap_bh->b_data))
> - break;
> - }
> + /*
> + * If the inode bitmap isn't in cache then the
> + * optimisation may end up performing two reads instead
> + * of one, so skip it.
> + */
> + if (!buffer_uptodate(bitmap_bh)) {
> brelse(bitmap_bh);
> - if (i == start + inodes_per_block) {
> - /* all other inodes are free, so skip I/O */
> - memset(bh->b_data, 0, bh->b_size);
> - set_buffer_uptodate(bh);
> - unlock_buffer(bh);
> - goto has_buffer;
> - }
> + goto make_io;
> + }
> + for (i = start; i < start + inodes_per_block; i++) {
> + if (i == inode_offset)
> + continue;
> + if (ext4_test_bit(i, bitmap_bh->b_data))
> + break;
> }
> + brelse(bitmap_bh);
> + if (i == start + inodes_per_block) {
> + /* all other inodes are free, so skip I/O */
> + memset(bh->b_data, 0, bh->b_size);
> + set_buffer_uptodate(bh);
> + unlock_buffer(bh);
> + goto has_buffer;
> + }
> + }
>
> make_io:
> - /*
> - * If we need to do any I/O, try to pre-readahead extra
> - * blocks from the inode table.
> - */
> - blk_start_plug(&plug);
> - if (EXT4_SB(sb)->s_inode_readahead_blks) {
> - ext4_fsblk_t b, end, table;
> - unsigned num;
> - __u32 ra_blks = EXT4_SB(sb)->s_inode_readahead_blks;
> -
> - table = ext4_inode_table(sb, gdp);
> - /* s_inode_readahead_blks is always a power of 2 */
> - b = block & ~((ext4_fsblk_t) ra_blks - 1);
> - if (table > b)
> - b = table;
> - end = b + ra_blks;
> - num = EXT4_INODES_PER_GROUP(sb);
> - if (ext4_has_group_desc_csum(sb))
> - num -= ext4_itable_unused_count(sb, gdp);
> - table += num / inodes_per_block;
> - if (end > table)
> - end = table;
> - while (b <= end)
> - ext4_sb_breadahead_unmovable(sb, b++);
> - }
> + /*
> + * If we need to do any I/O, try to pre-readahead extra
> + * blocks from the inode table.
> + */
> + blk_start_plug(&plug);
> + if (EXT4_SB(sb)->s_inode_readahead_blks) {
> + ext4_fsblk_t b, end, table;
> + unsigned num;
> + __u32 ra_blks = EXT4_SB(sb)->s_inode_readahead_blks;
> +
> + table = ext4_inode_table(sb, gdp);
> + /* s_inode_readahead_blks is always a power of 2 */
> + b = block & ~((ext4_fsblk_t) ra_blks - 1);
> + if (table > b)
> + b = table;
> + end = b + ra_blks;
> + num = EXT4_INODES_PER_GROUP(sb);
> + if (ext4_has_group_desc_csum(sb))
> + num -= ext4_itable_unused_count(sb, gdp);
> + table += num / inodes_per_block;
> + if (end > table)
> + end = table;
> + while (b <= end)
> + ext4_sb_breadahead_unmovable(sb, b++);
> + }
>
> - /*
> - * There are other valid inodes in the buffer, this inode
> - * has in-inode xattrs, or we don't have this inode in memory.
> - * Read the block from disk.
> - */
> - trace_ext4_load_inode(sb, ino);
> - ext4_read_bh_nowait(bh, REQ_META | REQ_PRIO, NULL);
> - blk_finish_plug(&plug);
> - wait_on_buffer(bh);
> - ext4_simulate_fail_bh(sb, bh, EXT4_SIM_INODE_EIO);
> - if (!buffer_uptodate(bh)) {
> - if (ret_block)
> - *ret_block = block;
> - brelse(bh);
> - return -EIO;
> - }
> + /*
> + * There are other valid inodes in the buffer, this inode
> + * has in-inode xattrs, or we don't have this inode in memory.
> + * Read the block from disk.
> + */
> + trace_ext4_load_inode(sb, ino);
> + ext4_read_bh_nowait(bh, REQ_META | REQ_PRIO, NULL);
> + blk_finish_plug(&plug);
> + wait_on_buffer(bh);
> + ext4_simulate_fail_bh(sb, bh, EXT4_SIM_INODE_EIO);
> + if (!buffer_uptodate(bh)) {
> + if (ret_block)
> + *ret_block = block;
> + brelse(bh);
> + return -EIO;
> }
> has_buffer:
> iloc->bh = bh;
> --
> 2.31.1
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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