2011-06-30 01:45:02

by Theodore Ts'o

Subject: [PATCH] ext4: remove loop around bio_alloc()

These days, bio_alloc() is guaranteed to never fail (as long as nvecs
is less than BIO_MAX_PAGES), so we don't need the loop around the
struct bio allocation.

Signed-off-by: "Theodore Ts'o" <[email protected]>
---
fs/ext4/page-io.c | 6 +-----
1 files changed, 1 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 7bb8f76..430c401 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -285,11 +285,7 @@ static int io_submit_init(struct ext4_io_submit *io,
io_end = ext4_init_io_end(inode, GFP_NOFS);
if (!io_end)
return -ENOMEM;
- do {
- bio = bio_alloc(GFP_NOIO, nvecs);
- nvecs >>= 1;
- } while (bio == NULL);

2011-06-30 02:12:26

by Steven Liu

Subject: Re: [PATCH] ext4: remove loop around bio_alloc()

Hi Ted,

2011/6/30 Theodore Ts'o <[email protected]>:
> These days, bio_alloc() is guaranteed to never fail (as long as nvecs
> is less than BIO_MAX_PAGES), so we don't need the loop around the
> struct bio allocation.
>
> Signed-off-by: "Theodore Ts'o" <[email protected]>
> ---
> ?fs/ext4/page-io.c | ? ?6 +-----
> ?1 files changed, 1 insertions(+), 5 deletions(-)
>
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 7bb8f76..430c401 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -285,11 +285,7 @@ static int io_submit_init(struct ext4_io_submit *io,
> ? ? ? ?io_end = ext4_init_io_end(inode, GFP_NOFS);
> ? ? ? ?if (!io_end)
> ? ? ? ? ? ? ? ?return -ENOMEM;
> - ? ? ? do {
> - ? ? ? ? ? ? ? bio = bio_alloc(GFP_NOIO, nvecs);
> - ? ? ? ? ? ? ? nvecs >>= 1;
> - ? ? ? } while (bio == NULL);
> -
> + ? ? ? bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
Is this needn't to check if bio_alloc success?

> ? ? ? ?bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
> ? ? ? ?bio->bi_bdev = bh->b_bdev;
> ? ? ? ?bio->bi_private = io->io_end = io_end;
> --
> 1.7.4.1.22.gec8e1.dirty
>
> --
Asked-by: LiuQi <[email protected]>

2011-06-30 02:15:06

by Steven Liu

Subject: Re: [PATCH] ext4: remove loop around bio_alloc()

2011/6/30 Theodore Ts'o <[email protected]>:
> These days, bio_alloc() is guaranteed to never fail (as long as nvecs
> is less than BIO_MAX_PAGES), so we don't need the loop around the
> struct bio allocation.
>
> Signed-off-by: "Theodore Ts'o" <[email protected]>
> ---
> ?fs/ext4/page-io.c | ? ?6 +-----
> ?1 files changed, 1 insertions(+), 5 deletions(-)
>
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 7bb8f76..430c401 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -285,11 +285,7 @@ static int io_submit_init(struct ext4_io_submit *io,
> ? ? ? ?io_end = ext4_init_io_end(inode, GFP_NOFS);
> ? ? ? ?if (!io_end)
> ? ? ? ? ? ? ? ?return -ENOMEM;
> - ? ? ? do {
> - ? ? ? ? ? ? ? bio = bio_alloc(GFP_NOIO, nvecs);
> - ? ? ? ? ? ? ? nvecs >>= 1;
> - ? ? ? } while (bio == NULL);
> -
> + ? ? ? bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
I think , If this do not need to loop around the struct bio allocation
insurance, if it check allocation value and give the faild message,
maybe better. is it?
> ? ? ? ?bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
> ? ? ? ?bio->bi_bdev = bh->b_bdev;
> ? ? ? ?bio->bi_private = io->io_end = io_end;
> --
> 1.7.4.1.22.gec8e1.dirty
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to [email protected]
> More majordomo info at ?http://vger.kernel.org/majordomo-info.html
>

2011-06-30 02:20:35

by Theodore Ts'o

Subject: Re: [PATCH] ext4: remove loop around bio_alloc()

On Thu, Jun 30, 2011 at 10:12:25AM +0800, Steven Liu wrote:
> > + ? ? ? bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
> Is this needn't to check if bio_alloc success?

No, that was the point of this patch. See the commit description.
Also see the comment for bio_alloc() in fs/bio.c, and note that
the __GFP_WAIT bit is set in GFP_NOFS.

Regards,

- Ted