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Message-ID: <20240105101723.gl5ew2mkhtn4nyyg@quack3> Date: Fri, 5 Jan 2024 11:17:23 +0100 From: Jan Kara <jack@...e.cz> To: Zhang Yi <yi.zhang@...weicloud.com> Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz, yi.zhang@...wei.com, chengzhihao1@...wei.com, yukuai3@...wei.com Subject: Re: [PATCH v3 3/6] ext4: correct the hole length returned by ext4_map_blocks() On Fri 05-01-24 11:30:15, Zhang Yi wrote: > From: Zhang Yi <yi.zhang@...wei.com> > > In ext4_map_blocks(), if we can't find a range of mapping in the > extents cache, we are calling ext4_ext_map_blocks() to search the real > path and ext4_ext_determine_hole() to determine the hole range. But if > the querying range was partially or completely overlaped by a delalloc > extent, we can't find it in the real extent path, so the returned hole > length could be incorrect. > > Fortunately, ext4_ext_put_gap_in_cache() have already handle delalloc > extent, but it searches start from the expanded hole_start, doesn't > start from the querying range, so the delalloc extent found could not be > the one that overlaped the querying range, plus, it also didn't adjust > the hole length. Let's just remove ext4_ext_put_gap_in_cache(), handle > delalloc and insert adjusted hole extent in ext4_ext_determine_hole(). > > Signed-off-by: Zhang Yi <yi.zhang@...wei.com> > Suggested-by: Jan Kara <jack@...e.cz> Thanks! Looks good. Feel free to add: Reviewed-by: Jan Kara <jack@...e.cz> Honza > --- > fs/ext4/extents.c | 111 +++++++++++++++++++++++++++++----------------- > 1 file changed, 70 insertions(+), 41 deletions(-) > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index d5efe076d3d3..e0b7e48c4c67 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -2229,7 +2229,7 @@ static int ext4_fill_es_cache_info(struct inode *inode, > > > /* > - * ext4_ext_determine_hole - determine hole around given block > + * ext4_ext_find_hole - find hole around given block according to the given path > * @inode: inode we lookup in > * @path: path in extent tree to @lblk > * @lblk: pointer to logical block around which we want to determine hole > @@ -2241,9 +2241,9 @@ static int ext4_fill_es_cache_info(struct inode *inode, > * The function returns the length of a hole starting at @lblk. We update @lblk > * to the beginning of the hole if we managed to find it. > */ > -static ext4_lblk_t ext4_ext_determine_hole(struct inode *inode, > - struct ext4_ext_path *path, > - ext4_lblk_t *lblk) > +static ext4_lblk_t ext4_ext_find_hole(struct inode *inode, > + struct ext4_ext_path *path, > + ext4_lblk_t *lblk) > { > int depth = ext_depth(inode); > struct ext4_extent *ex; > @@ -2270,30 +2270,6 @@ static ext4_lblk_t ext4_ext_determine_hole(struct inode *inode, > return len; > } > > -/* > - * ext4_ext_put_gap_in_cache: > - * calculate boundaries of the gap that the requested block fits into > - * and cache this gap > - */ > -static void > -ext4_ext_put_gap_in_cache(struct inode *inode, ext4_lblk_t hole_start, > - ext4_lblk_t hole_len) > -{ > - struct extent_status es; > - > - ext4_es_find_extent_range(inode, &ext4_es_is_delayed, hole_start, > - hole_start + hole_len - 1, &es); > - if (es.es_len) { > - /* There's delayed extent containing lblock? */ > - if (es.es_lblk <= hole_start) > - return; > - hole_len = min(es.es_lblk - hole_start, hole_len); > - } > - ext_debug(inode, " -> %u:%u\n", hole_start, hole_len); > - ext4_es_insert_extent(inode, hole_start, hole_len, ~0, > - EXTENT_STATUS_HOLE); > -} > - > /* > * ext4_ext_rm_idx: > * removes index from the index block. > @@ -4062,6 +4038,69 @@ static int get_implied_cluster_alloc(struct super_block *sb, > return 0; > } > > +/* > + * Determine hole length around the given logical block, first try to > + * locate and expand the hole from the given @path, and then adjust it > + * if it's partially or completely converted to delayed extents, insert > + * it into the extent cache tree if it's indeed a hole, finally return > + * the length of the determined extent. > + */ > +static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode, > + struct ext4_ext_path *path, > + ext4_lblk_t lblk) > +{ > + ext4_lblk_t hole_start, len; > + struct extent_status es; > + > + hole_start = lblk; > + len = ext4_ext_find_hole(inode, path, &hole_start); > +again: > + ext4_es_find_extent_range(inode, &ext4_es_is_delayed, hole_start, > + hole_start + len - 1, &es); > + if (!es.es_len) > + goto insert_hole; > + > + /* > + * There's a delalloc extent in the hole, handle it if the delalloc > + * extent is in front of, behind and straddle the queried range. > + */ > + if (lblk >= es.es_lblk + es.es_len) { > + /* > + * The delalloc extent is in front of the queried range, > + * find again from the queried start block. > + */ > + len -= lblk - hole_start; > + hole_start = lblk; > + goto again; > + } else if (in_range(lblk, es.es_lblk, es.es_len)) { > + /* > + * The delalloc extent containing lblk, it must have been > + * added after ext4_map_blocks() checked the extent status > + * tree, adjust the length to the delalloc extent's after > + * lblk. > + */ > + len = es.es_lblk + es.es_len - lblk; > + return len; > + } else { > + /* > + * The delalloc extent is partially or completely behind > + * the queried range, update hole length until the > + * beginning of the delalloc extent. > + */ > + len = min(es.es_lblk - hole_start, len); > + } > + > +insert_hole: > + /* Put just found gap into cache to speed up subsequent requests */ > + ext_debug(inode, " -> %u:%u\n", hole_start, len); > + ext4_es_insert_extent(inode, hole_start, len, ~0, EXTENT_STATUS_HOLE); > + > + /* Update hole_len to reflect hole size after lblk */ > + if (hole_start != lblk) > + len -= lblk - hole_start; > + > + return len; > +} > > /* > * Block allocation/map/preallocation routine for extents based files > @@ -4179,22 +4218,12 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, > * we couldn't try to create block if create flag is zero > */ > if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) { > - ext4_lblk_t hole_start, hole_len; > + ext4_lblk_t len; > > - hole_start = map->m_lblk; > - hole_len = ext4_ext_determine_hole(inode, path, &hole_start); > - /* > - * put just found gap into cache to speed up > - * subsequent requests > - */ > - ext4_ext_put_gap_in_cache(inode, hole_start, hole_len); > + len = ext4_ext_determine_insert_hole(inode, path, map->m_lblk); > > - /* Update hole_len to reflect hole size after map->m_lblk */ > - if (hole_start != map->m_lblk) > - hole_len -= map->m_lblk - hole_start; > map->m_pblk = 0; > - map->m_len = min_t(unsigned int, map->m_len, hole_len); > - > + map->m_len = min_t(unsigned int, map->m_len, len); > goto out; > } > > -- > 2.39.2 > -- Jan Kara <jack@...e.com> SUSE Labs, CR
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