On 6/17/25 19:37, Chao Yu via Linux-f2fs-devel wrote:
On 6/17/25 13:55, 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.
Signed-off-by: Jianan Huang <huangjia...@xiaomi.com>
Signed-off-by: Sheng Yong <shengyo...@xiaomi.com>
---
fs/f2fs/data.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 31e892842625..c7773b09d83f 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2303,7 +2303,8 @@ 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,
+ max(nr_pages, cc->nr_cpages) - i,
Hi Jianan,
e.g.
User wants to read page [1, 5],
page #1,2,3,4 locates in compressed block #1000,1001,1003,
page #5 locate in compressed block #1004,1005
It submits first bio w/ block #1000,1001
It allocates second bio w/ size of max(nr_pages=1, nr_cpages=3) - 2 = 1 ?
However block #1003 and block #1004,1005 can be readed in one bio, we
should allocate larger bio for last continuous blocks which cross clusters.
Hi, Chao,
I think `max(nr_pages, cc->nr_cpages) - i` can reserve enough vectors in bio
for later reads. IIUC, the case above is:
read page #1,2,3,4 at blkaddr #1000,1001,1003:
* nr_pages=5, cpages=3, for the first bio1, vec=max(5,3)-0=5 (2 vecs are used)
for the second bio2, vec=max(5,3)-2=3 (1 vec is used)
read page #5 at blkaddr #1004,1005, prev bio2 is still available
* nr_pages=1, cpages=2, prev bio2, 2 vecs left
For case: page #1,2,3,4 at compressed blkaddr #1000,1001,1003
page #5,6,7,8 at compressed blkaddr #1004,1005,1006
If we are reading page[1,5], we could do calculation as the following?
max_nr_pages=align(nr_pages, cluster_size)
max(max_nr_pages, cc->nr_cpages) - i
thanks,
shengyong
f2fs_ra_op_flags(rac),
folio->index, for_write);
if (IS_ERR(bio)) {
@@ -2373,7 +2374,6 @@ static int f2fs_mpage_readpages(struct inode *inode,
pgoff_t index;
#endif
unsigned nr_pages = rac ? readahead_count(rac) : 1;
- unsigned max_nr_pages = nr_pages;
Maybe we can align both start and end of read range w/ cluster_size, and use
start and end for max_nr_pages calculation, then pass it to
f2fs_read_{multi,single}_pages(), something like this?
max_nr_pages = round_up(end_idx, cluster_size) -
round_down(start_idx, cluster_size);
Its size should always cover size of all cpage and/or rpage.
Thanks,
int ret = 0;
map.m_pblk = 0;
@@ -2400,7 +2400,7 @@ static int f2fs_mpage_readpages(struct inode *inode,
/* there are remained compressed pages, submit them */
if (!f2fs_cluster_can_merge_page(&cc, index)) {
ret = f2fs_read_multi_pages(&cc, &bio,
- max_nr_pages,
+ nr_pages,
&last_block_in_bio,
rac, false);
f2fs_destroy_compress_ctx(&cc, false);
@@ -2432,7 +2432,7 @@ static int f2fs_mpage_readpages(struct inode *inode,
read_single_page:
#endif
- ret = f2fs_read_single_page(inode, folio, max_nr_pages, &map,
+ ret = f2fs_read_single_page(inode, folio, nr_pages, &map,
&bio, &last_block_in_bio, rac);
if (ret) {
#ifdef CONFIG_F2FS_FS_COMPRESSION
@@ -2450,7 +2450,7 @@ static int f2fs_mpage_readpages(struct inode *inode,
/* last page */
if (nr_pages == 1 && !f2fs_cluster_is_empty(&cc)) {
ret = f2fs_read_multi_pages(&cc, &bio,
- max_nr_pages,
+ nr_pages,
&last_block_in_bio,
rac, false);
f2fs_destroy_compress_ctx(&cc, false);
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