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--) { 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