RE: [f2fs-dev][PATCH RESEND] f2fs: avoid allocating failure in bio_alloc

[Chao Yu <chao2.yu@samsung.com>]

Hi Gu

> -----Original Message-----
> From: Gu Zheng [mailto:guz.fnst@cn.fujitsu.com]
> Sent: Monday, September 16, 2013 12:40 PM
> To: Chao Yu
> Cc: 'Kim Jaegeuk'; linux-f2fs-devel@lists.sourceforge.net;
> linux-fsdevel@vger.kernel.org; linux-kernel@vger.kernel.org; '谭姝'
> Subject: Re: [f2fs-dev][PATCH RESEND] f2fs: avoid allocating failure in
bio_alloc
> 
> Hi Chao,
> 
> On 09/16/2013 11:26 AM, Chao Yu wrote:
> 
> > Hi Gu
> >
> >> -----Original Message-----
> >> From: Gu Zheng [mailto:guz.fnst@cn.fujitsu.com]
> >> Sent: Monday, September 16, 2013 10:09 AM
> >> To: Chao Yu
> >> Cc: Kim Jaegeuk; linux-f2fs-devel@lists.sourceforge.net;
> >> linux-fsdevel@vger.kernel.org; linux-kernel@vger.kernel.org; 谭姝
> >> Subject: Re: [f2fs-dev][PATCH RESEND] f2fs: avoid allocating failure
> >> in
> > bio_alloc
> >>
> >> Hi Chao,
> >>
> >> On 09/13/2013 09:27 PM, Chao Yu wrote:
> >>
> >>> This patch add macro MAX_BIO_BLOCKS to limit value of npages in
> >>> f2fs_bio_alloc, it can avoid allocating failure in bio_alloc caused
> >>> by npages is larger than UIO_MAXIOV.
> >>
> >> As I know bio_alloc is based of *fs_bio_set* pool, without the
> >> limitation
> > of
> >> UIO_MAXIOV, am I missing something?
> >
> > Here is the code in bio.c, fs_bio_set is as the actual parameter pass
> > to bs without being inited.
> 
> fs_bio_set was initiated early in the bio subsystem init.
> 
> > So it may have opportunity to return NULL in this function.
> 
> It may be, but may not be the thread you mentioned below.
> 
> > ---
> > Bio.c
> > struct bio *bio_alloc_bioset(gfp_t gfp_mask, int nr_iovecs, struct
> > bio_set
> > *bs)
> > {
> > ......
> > 	if (!bs) {
> > 		if (nr_iovecs > UIO_MAXIOV)
> > 			return NULL;
> > ---
> > I did the abnormal test: modify the max_sectors_kb in
> > /sys/block/sdx/queue to 32767 for a disk with f2fs format, and I got a
> > segfualt in f2fs_bio_alloc after the img mounted.
> > Is there anyting I missed?
> 
> Hmm, this change will also trigger bvec_alloc failed, did you add some
traces to
> debug this?

I reviewed the code in bio_alloc, and then trace the process of bio_alloc
for verification.
It indicate that bvec_alloc() will fail on the condition that nr_iovecs is
greater than BIO_MAX_PAGES.
The patch should be updated for that.

I am sorry about the mistake in this patch, and thanks for the reviewing and
reminding.

> 
> Regards,
> Gu
> 
> >
> >>
> >> Thanks,
> >> Gu
> >>
> >>>
> >>> Signed-off-by: Yu Chao <chao2.yu@samsung.com>
> >>>  ---
> >>>  fs/f2fs/segment.c |    4 +++-
> >>>  fs/f2fs/segment.h |    3 +++
> >>>  2 files changed, 6 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c index
> >>> 09af9c7..bd79bbe 100644
> >>> --- a/fs/f2fs/segment.c
> >>> +++ b/fs/f2fs/segment.c
> >>> @@ -657,6 +657,7 @@ static void submit_write_page(struct
> >>> f2fs_sb_info *sbi, struct page *page,
> >>>                                 block_t blk_addr, enum page_type
> >> type)
> >>> {
> >>>         struct block_device *bdev = sbi->sb->s_bdev;
> >>> +       int bio_blocks;
> >>>
> >>>         verify_block_addr(sbi, blk_addr);
> >>>
> >>> @@ -676,7 +677,8 @@ retry:
> >>>                         goto retry;
> >>>                 }
> >>>
> >>> -               sbi->bio[type] = f2fs_bio_alloc(bdev,
> > max_hw_blocks(sbi));
> >>> +               bio_blocks = MAX_BIO_BLOCKS(max_hw_blocks(sbi));
> >>> +               sbi->bio[type] = f2fs_bio_alloc(bdev, bio_blocks);
> >>>                 sbi->bio[type]->bi_sector =
> SECTOR_FROM_BLOCK(sbi,
> >>> blk_addr);
> >>>                 sbi->bio[type]->bi_private = priv;
> >>>                 /*
> >>> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h index
> >>> bdd10ea..6352af1 100644
> >>> --- a/fs/f2fs/segment.h
> >>> +++ b/fs/f2fs/segment.h
> >>> @@ -9,6 +9,7 @@
> >>>   * published by the Free Software Foundation.
> >>>   */
> >>>  #include <linux/blkdev.h>
> >>> +#include <linux/uio.h>
> >>>
> >>>  /* constant macro */
> >>>  #define NULL_SEGNO                     ((unsigned int)(~0))
> >>> @@ -90,6 +91,8 @@
> >>>         (blk_addr << ((sbi)->log_blocksize - F2FS_LOG_SECTOR_SIZE))
> >>> #define SECTOR_TO_BLOCK(sbi, sectors)
> >> \
> >>>         (sectors >> ((sbi)->log_blocksize - F2FS_LOG_SECTOR_SIZE))
> >>> +#define MAX_BIO_BLOCKS(max_hw_blocks)
> >> \
> >>> +       (min((int)max_hw_blocks, UIO_MAXIOV))
> >>>
> >>>  /* during checkpoint, bio_private is used to synchronize the last
> >>> bio */  struct bio_private {
> >>> ---
> >>>
> >>> --
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> >
> >
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> 
> 
> =

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