On 6/25/25 14:49, Jianan Huang wrote:
> When fewer pages are read, nr_pages may be smaller than nr_cpages. Due
> to the nr_vecs limit, the compressed pages will be split into multiple
> bios and then merged at the block level. In this case, nr_cpages should
> be used to pre-allocate bvecs.
> To handle this case, align max_nr_pages to cluster_size, which should be
> enough for all compressed pages.
>
> Signed-off-by: Jianan Huang <huangjia...@xiaomi.com>
> Signed-off-by: Sheng Yong <shengyo...@xiaomi.com>
> ---
> Changes since v2:
> - Initialize index only for compressed files.
> Changes since v1:
> - Use aligned nr_pages instead of nr_cpages to pre-allocate bvecs.
>
> fs/f2fs/data.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 31e892842625..d071d9f6a811 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -2303,7 +2303,7 @@ int f2fs_read_multi_pages(struct compress_ctx *cc,
> struct bio **bio_ret,
> }
>
> if (!bio) {
> - bio = f2fs_grab_read_bio(inode, blkaddr, nr_pages,
> + bio = f2fs_grab_read_bio(inode, blkaddr, nr_pages - i,
Jianan,
Another case:
read page #0,1,2,3 from block #1000,1001,1002, cluster_size=4.
nr_pages=4
max_nr_pages=round_up(0+4,4)-round_down(0,4)=4
f2fs_mpage_readpages() calls f2fs_read_multi_pages() when nr_pages=1, at
that time, max_nr_pages equals to 1 as well.
f2fs_grab_read_bio(..., 1 - 0,...) allocate bio w/ 1 vec capacity, however,
we need at least 3 vecs to merge all cpages, right?
Thanks,
> f2fs_ra_op_flags(rac),
> folio->index, for_write);
> if (IS_ERR(bio)) {
> @@ -2376,6 +2376,14 @@ static int f2fs_mpage_readpages(struct inode *inode,
> unsigned max_nr_pages = nr_pages;
> int ret = 0;
>
> +#ifdef CONFIG_F2FS_FS_COMPRESSION
> + if (f2fs_compressed_file(inode)) {
> + index = rac ? readahead_index(rac) : folio->index;
> + max_nr_pages = round_up(index + nr_pages, cc.cluster_size) -
> + round_down(index, cc.cluster_size);
> + }
> +#endif
> +
> map.m_pblk = 0;
> map.m_lblk = 0;
> map.m_len = 0;
> @@ -2385,7 +2393,7 @@ static int f2fs_mpage_readpages(struct inode *inode,
> map.m_seg_type = NO_CHECK_TYPE;
> map.m_may_create = false;
>
> - for (; nr_pages; nr_pages--) {
> + for (; nr_pages; nr_pages--, max_nr_pages--) {
> if (rac) {
> folio = readahead_folio(rac);
> prefetchw(&folio->flags);
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