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Date: Sun, 12 May 2024 23:51:47 +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 10/10] ext4: make ext4_da_map_blocks() buffer_head
unaware
On Wed 08-05-24 14:12:20, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
>
> After calling the ext4_da_map_blocks(), a delalloc extent state could
> be identified through the EXT4_MAP_DELAYED flag in map. So factor out
> buffer_head related handles in ext4_da_map_blocks(), make this function
> buffer_head unaware and becomes a common helper, and also update the
> stale function commtents, preparing for the iomap da write path in the
> future.
>
> 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/inode.c | 63 ++++++++++++++++++++++++-------------------------
> 1 file changed, 31 insertions(+), 32 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index c56386d1b10d..1dba5337382a 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1745,36 +1745,32 @@ static int ext4_insert_delayed_blocks(struct inode *inode, ext4_lblk_t lblk,
> }
>
> /*
> - * This function is grabs code from the very beginning of
> - * ext4_map_blocks, but assumes that the caller is from delayed write
> - * time. This function looks up the requested blocks and sets the
> - * buffer delay bit under the protection of i_data_sem.
> + * Looks up the requested blocks and sets the delalloc extent map.
> + * First try to look up for the extent entry that contains the requested
> + * blocks in the extent status tree without i_data_sem, then try to look
> + * up for the ondisk extent mapping with i_data_sem in read mode,
> + * finally hold i_data_sem in write mode, looks up again and add a
> + * delalloc extent entry if it still couldn't find any extent. Pass out
> + * the mapped extent through @map and return 0 on success.
> */
> -static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
> - struct buffer_head *bh)
> +static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map)
> {
> struct extent_status es;
> int retval;
> - sector_t invalid_block = ~((sector_t) 0xffff);
> #ifdef ES_AGGRESSIVE_TEST
> struct ext4_map_blocks orig_map;
>
> memcpy(&orig_map, map, sizeof(*map));
> #endif
>
> - if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
> - invalid_block = ~0;
> -
> map->m_flags = 0;
> ext_debug(inode, "max_blocks %u, logical block %lu\n", map->m_len,
> (unsigned long) map->m_lblk);
>
> /* Lookup extent status tree firstly */
> if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
> - retval = es.es_len - (map->m_lblk - es.es_lblk);
> - if (retval > map->m_len)
> - retval = map->m_len;
> - map->m_len = retval;
> + map->m_len = min_t(unsigned int, map->m_len,
> + es.es_len - (map->m_lblk - es.es_lblk));
>
> if (ext4_es_is_hole(&es))
> goto add_delayed;
> @@ -1784,10 +1780,8 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
> * Delayed extent could be allocated by fallocate.
> * So we need to check it.
> */
> - if (ext4_es_is_delayed(&es) && !ext4_es_is_unwritten(&es)) {
> - map_bh(bh, inode->i_sb, invalid_block);
> - set_buffer_new(bh);
> - set_buffer_delay(bh);
> + if (ext4_es_is_delonly(&es)) {
> + map->m_flags |= EXT4_MAP_DELAYED;
> return 0;
> }
>
> @@ -1802,7 +1796,7 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
> #ifdef ES_AGGRESSIVE_TEST
> ext4_map_blocks_es_recheck(NULL, inode, map, &orig_map, 0);
> #endif
> - return retval;
> + return 0;
> }
>
> /*
> @@ -1816,7 +1810,7 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
> retval = ext4_map_query_blocks(NULL, inode, map);
> up_read(&EXT4_I(inode)->i_data_sem);
> if (retval)
> - return retval;
> + return retval < 0 ? retval : 0;
>
> add_delayed:
> down_write(&EXT4_I(inode)->i_data_sem);
> @@ -1828,10 +1822,8 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
> * the extent status tree.
> */
> if (ext4_es_lookup_extent(inode, map->m_lblk, NULL, &es)) {
> - retval = es.es_len - (map->m_lblk - es.es_lblk);
> - if (retval > map->m_len)
> - retval = map->m_len;
> - map->m_len = retval;
> + map->m_len = min_t(unsigned int, map->m_len,
> + es.es_len - (map->m_lblk - es.es_lblk));
>
> if (!ext4_es_is_hole(&es)) {
> up_write(&EXT4_I(inode)->i_data_sem);
> @@ -1841,18 +1833,14 @@ static int ext4_da_map_blocks(struct inode *inode, struct ext4_map_blocks *map,
> retval = ext4_map_query_blocks(NULL, inode, map);
> if (retval) {
> up_write(&EXT4_I(inode)->i_data_sem);
> - return retval;
> + return retval < 0 ? retval : 0;
> }
> }
>
> + map->m_flags |= EXT4_MAP_DELAYED;
> retval = ext4_insert_delayed_blocks(inode, map->m_lblk, map->m_len);
> up_write(&EXT4_I(inode)->i_data_sem);
> - if (retval)
> - return retval;
>
> - map_bh(bh, inode->i_sb, invalid_block);
> - set_buffer_new(bh);
> - set_buffer_delay(bh);
> return retval;
> }
>
> @@ -1872,11 +1860,15 @@ int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
> struct buffer_head *bh, int create)
> {
> struct ext4_map_blocks map;
> + sector_t invalid_block = ~((sector_t) 0xffff);
> int ret = 0;
>
> BUG_ON(create == 0);
> BUG_ON(bh->b_size != inode->i_sb->s_blocksize);
>
> + if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
> + invalid_block = ~0;
> +
> map.m_lblk = iblock;
> map.m_len = 1;
>
> @@ -1885,10 +1877,17 @@ int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
> * preallocated blocks are unmapped but should treated
> * the same as allocated blocks.
> */
> - ret = ext4_da_map_blocks(inode, &map, bh);
> - if (ret <= 0)
> + ret = ext4_da_map_blocks(inode, &map);
> + if (ret < 0)
> return ret;
>
> + if (map.m_flags & EXT4_MAP_DELAYED) {
> + map_bh(bh, inode->i_sb, invalid_block);
> + set_buffer_new(bh);
> + set_buffer_delay(bh);
> + return 0;
> + }
> +
> map_bh(bh, inode->i_sb, map.m_pblk);
> ext4_update_bh_state(bh, map.m_flags);
>
> --
> 2.39.2
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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