Messages in this thread Patch in this message | | | Subject | Re: [PATCH v2] erofs: fix bio->bi_max_vecs behavior change | From | Chao Yu <> | Date | Fri, 19 Mar 2021 10:15:18 +0800 |
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On 2021/3/6 12:04, Gao Xiang wrote: > From: Gao Xiang <hsiangkao@redhat.com> > > Martin reported an issue that directory read could be hung on the > latest -rc kernel with some certain image. The root cause is that > commit baa2c7c97153 ("block: set .bi_max_vecs as actual allocated > vector number") changes .bi_max_vecs behavior. bio->bi_max_vecs > is set as actual allocated vector number rather than the requested > number now. > > Let's avoid using .bi_max_vecs completely instead. > > Reported-by: Martin DEVERA <devik@eaxlabs.cz> > Signed-off-by: Gao Xiang <hsiangkao@redhat.com> > --- > change since v1: > - since bio->bi_max_vecs doesn't record extent blocks anymore, > introduce a remaining extent block to avoid extent excess. > > fs/erofs/data.c | 28 +++++++++++----------------- > 1 file changed, 11 insertions(+), 17 deletions(-) > > diff --git a/fs/erofs/data.c b/fs/erofs/data.c > index f88851c5c250..1249e74b3bf0 100644 > --- a/fs/erofs/data.c > +++ b/fs/erofs/data.c > @@ -129,6 +129,7 @@ static inline struct bio *erofs_read_raw_page(struct bio *bio, > struct page *page, > erofs_off_t *last_block, > unsigned int nblocks, > + unsigned int *eblks, > bool ra) > { > struct inode *const inode = mapping->host; > @@ -145,8 +146,7 @@ static inline struct bio *erofs_read_raw_page(struct bio *bio, > > /* note that for readpage case, bio also equals to NULL */ > if (bio && > - /* not continuous */ > - *last_block + 1 != current_block) { > + (*last_block + 1 != current_block || !*eblks)) {
Xiang,
I found below function during checking bi_max_vecs usage in f2fs:
/** * bio_full - check if the bio is full * @bio: bio to check * @len: length of one segment to be added * * Return true if @bio is full and one segment with @len bytes can't be * added to the bio, otherwise return false */ static inline bool bio_full(struct bio *bio, unsigned len) { if (bio->bi_vcnt >= bio->bi_max_vecs) return true;
if (bio->bi_iter.bi_size > UINT_MAX - len) return true;
return false; }
Could you please check that whether it will be better to use bio_full() rather than using left-space-in-bio maintained by erofs itself? something like:
if (bio && (bio_full(bio, PAGE_SIZE) || /* not continuous */ (*last_block + 1 != current_block))
I'm thinking we need to decouple bio detail implementation as much as possible, to avoid regression whenever bio used/max size definition updates, though I've no idea how to fix f2fs case.
Let me know if you have other concern.
Thanks,
> submit_bio_retry: > submit_bio(bio); > bio = NULL; > @@ -216,7 +216,8 @@ static inline struct bio *erofs_read_raw_page(struct bio *bio, > if (nblocks > DIV_ROUND_UP(map.m_plen, PAGE_SIZE)) > nblocks = DIV_ROUND_UP(map.m_plen, PAGE_SIZE); > > - bio = bio_alloc(GFP_NOIO, bio_max_segs(nblocks)); > + *eblks = bio_max_segs(nblocks); > + bio = bio_alloc(GFP_NOIO, *eblks); > > bio->bi_end_io = erofs_readendio; > bio_set_dev(bio, sb->s_bdev); > @@ -229,16 +230,8 @@ static inline struct bio *erofs_read_raw_page(struct bio *bio, > /* out of the extent or bio is full */ > if (err < PAGE_SIZE) > goto submit_bio_retry; > - > + --*eblks; > *last_block = current_block; > - > - /* shift in advance in case of it followed by too many gaps */ > - if (bio->bi_iter.bi_size >= bio->bi_max_vecs * PAGE_SIZE) { > - /* err should reassign to 0 after submitting */ > - err = 0; > - goto submit_bio_out; > - } > - > return bio; > > err_out: > @@ -252,7 +245,6 @@ static inline struct bio *erofs_read_raw_page(struct bio *bio, > > /* if updated manually, continuous pages has a gap */ > if (bio) > -submit_bio_out: > submit_bio(bio); > return err ? ERR_PTR(err) : NULL; > } > @@ -264,23 +256,26 @@ static inline struct bio *erofs_read_raw_page(struct bio *bio, > static int erofs_raw_access_readpage(struct file *file, struct page *page) > { > erofs_off_t last_block; > + unsigned int eblks; > struct bio *bio; > > trace_erofs_readpage(page, true); > > bio = erofs_read_raw_page(NULL, page->mapping, > - page, &last_block, 1, false); > + page, &last_block, 1, &eblks, false); > > if (IS_ERR(bio)) > return PTR_ERR(bio); > > - DBG_BUGON(bio); /* since we have only one bio -- must be NULL */ > + if (bio) > + submit_bio(bio); > return 0; > } > > static void erofs_raw_access_readahead(struct readahead_control *rac) > { > erofs_off_t last_block; > + unsigned int eblks; > struct bio *bio = NULL; > struct page *page; > > @@ -291,7 +286,7 @@ static void erofs_raw_access_readahead(struct readahead_control *rac) > prefetchw(&page->flags); > > bio = erofs_read_raw_page(bio, rac->mapping, page, &last_block, > - readahead_count(rac), true); > + readahead_count(rac), &eblks, true); > > /* all the page errors are ignored when readahead */ > if (IS_ERR(bio)) { > @@ -305,7 +300,6 @@ static void erofs_raw_access_readahead(struct readahead_control *rac) > put_page(page); > } > > - /* the rare case (end in gaps) */ > if (bio) > submit_bio(bio); > } >
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