Re: [PATCH v2] erofs: fix bio->bi_max_vecs behavior change
Hi Chao,
On Fri, Mar 19, 2021 at 10:15:18AM +0800, Chao Yu wrote:
> On 2021/3/6 12:04, Gao Xiang wrote:
...
> > + (*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.
Thanks for your suggestion.
Not quite sure I understand the idea... The original problem was that
when EROFS bio_alloc, the number of requested bvec also partially stood
for remaining blocks of the current on-disk extent to limit the read
length. but after that bio behavior change, bi_max_vec could be increased
internally by block layer (e.g. 1 --> 4), so bi_max_vecs is no longer
as what we expect (I mean passed-in). so could cause read request
out-of-bound or hung. That's why I decided to record it manually (never
rely on bio statistics anymore...)
Also btw, AFAIK, Jianan is still investigating to use iomap instead
(mainly resolve tail-packing inline path). And I'm also busy in big
pcluster and LZMA new features for the next cycle. So I think we might
leave it just as is and it would be replaced with iomap in the future.
Thanks,
Gao Xiang
>
> Let me know if you have other concern.
>
> Thanks,
Re: [PATCH v2] erofs: fix bio->bi_max_vecs behavior change
On 2021/3/6 12:04, Gao Xiang wrote:
From: Gao Xiang
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
Signed-off-by: Gao Xiang
---
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, _block, 1, false);
+ page, _block, 1, , 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
Re: [PATCH v2] erofs: fix bio->bi_max_vecs behavior change
On Mon, Mar 08, 2021 at 10:52:19AM +0800, Chao Yu wrote:
> On 2021/3/8 10:36, Gao Xiang wrote:
> > Hi Chao,
> >
> > On Mon, Mar 08, 2021 at 09:29:30AM +0800, Chao Yu wrote:
> > > On 2021/3/6 12:04, Gao Xiang wrote:
> > > > From: Gao Xiang
> > > >
> > > > 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
> > > > Signed-off-by: Gao Xiang
> > >
> > > Looks good to me, btw, it needs to Cc stable mailing list?
> > >
> > > Reviewed-by: Chao Yu
> > >
> >
> > Thanks for your review. <= 5.11 kernels are not impacted.
> > For now, this only impacts 5.12-rc due to a bio behavior
> > change (see commit baa2c7c97153). So personally I think
> > just leave as it is is fine.
>
> Okay, so that's fine if you send pull request before 5.12 formal release. ;)
Yeah, it's an urgent commit and have very negative impact.
I pushed out -fixes branch just now. After leaving in linux-next
for days, will upstream it then asap... :-(
Thanks,
Gao Xiang
>
> Thanks,
>
> >
> > Thanks,
> > Gao Xiang
> >
> > > Thanks,
> > >
> >
> > .
> >
>
Re: [PATCH v2] erofs: fix bio->bi_max_vecs behavior change
On 2021/3/8 10:36, Gao Xiang wrote:
Hi Chao,
On Mon, Mar 08, 2021 at 09:29:30AM +0800, Chao Yu wrote:
On 2021/3/6 12:04, Gao Xiang wrote:
From: Gao Xiang
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
Signed-off-by: Gao Xiang
Looks good to me, btw, it needs to Cc stable mailing list?
Reviewed-by: Chao Yu
Thanks for your review. <= 5.11 kernels are not impacted.
For now, this only impacts 5.12-rc due to a bio behavior
change (see commit baa2c7c97153). So personally I think
just leave as it is is fine.
Okay, so that's fine if you send pull request before 5.12 formal release. ;)
Thanks,
Thanks,
Gao Xiang
Thanks,
.
Re: [PATCH v2] erofs: fix bio->bi_max_vecs behavior change
Hi Chao,
On Mon, Mar 08, 2021 at 09:29:30AM +0800, Chao Yu wrote:
> On 2021/3/6 12:04, Gao Xiang wrote:
> > From: Gao Xiang
> >
> > 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
> > Signed-off-by: Gao Xiang
>
> Looks good to me, btw, it needs to Cc stable mailing list?
>
> Reviewed-by: Chao Yu
>
Thanks for your review. <= 5.11 kernels are not impacted.
For now, this only impacts 5.12-rc due to a bio behavior
change (see commit baa2c7c97153). So personally I think
just leave as it is is fine.
Thanks,
Gao Xiang
> Thanks,
>
Re: [PATCH v2] erofs: fix bio->bi_max_vecs behavior change
On 2021/3/6 12:04, Gao Xiang wrote:
From: Gao Xiang
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
Signed-off-by: Gao Xiang
Looks good to me, btw, it needs to Cc stable mailing list?
Reviewed-by: Chao Yu
Thanks,
[PATCH v2] erofs: fix bio->bi_max_vecs behavior change
From: Gao Xiang
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
Signed-off-by: Gao Xiang
---
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)) {
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, _block, 1, false);
+ page, _block, 1, , 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(>flags);
bio = erofs_read_raw_page(bio, rac->mapping, page, _block,
- readahead_count(rac), true);
+ readahead_count(rac), , 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);
}
--
2.20.1
