On 2025/6/30 19:23, Chao Yu wrote: > > On 6/25/25 17:50, Huang Jianan wrote: >> On 2025/6/25 17:48, Jianan Huang wrote: >>> On 2025/6/25 16:45, Chao Yu wrote: >>>> >>>> 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? >>>> >>> >>> Hi, chao, >>> >>> If we don't align nr_pages, then when entering f2fs_read_multi_pages, >>> we have nr_pages pages left, which belong to other clusters. >>> If this is the last page, we can simply pass nr_pages = 0. >>> >>> When allocating bio, we need: >>> 1. The cpages remaining in the current cluster, which should be >>> (nr_capges - i). >>> 2. The maximum cpages remaining in other clusters, which should be >>> max(nr_pages, cc->nr_cpages). >>> >> >> align(nr_pages, cc->nr_cpages), sorry for this. >> >>> So (nr_capges - i) + max(nr_pages, nr_cpages), should be enough for all >>> vecs? > > Jianan, > > What about getting rid of below change? and just passing max_nr_pages to > f2fs_read_multi_pages? Maybe there is a little bit waste for bio vector space, > but it will be more safe to reserve enough margin. > > + for (; nr_pages; nr_pages--, max_nr_pages--) { >
LGTM, updated in v4. Thanks, > Thanks, > >>> >>> Thanks, >>> >>> >>>> 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); >>>> >>> >> > _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel