Patchwork ext4: remove loop around bio_alloc()

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Submitter Theodore Ts'o
Date June 30, 2011, 1:44 a.m.
Message ID <1309398299-9988-1-git-send-email-tytso@mit.edu>
Download mbox | patch
Permalink /patch/102692/
State Accepted
Headers show

Comments

Theodore Ts'o - June 30, 2011, 1:44 a.m.
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" <tytso@mit.edu>
---
 fs/ext4/page-io.c |    6 +-----
 1 files changed, 1 insertions(+), 5 deletions(-)
Steven Liu - June 30, 2011, 2:12 a.m.
Hi Ted,

2011/6/30 Theodore Ts'o <tytso@mit.edu>:
> 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" <tytso@mit.edu>
> ---
>  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 <lingjiujianke@gmail.com>
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Steven Liu - June 30, 2011, 2:15 a.m.
2011/6/30 Theodore Ts'o <tytso@mit.edu>:
> 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" <tytso@mit.edu>
> ---
>  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
>
> --
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Theodore Ts'o - June 30, 2011, 2:20 a.m.
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
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Patch

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));
 	bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
 	bio->bi_bdev = bh->b_bdev;
 	bio->bi_private = io->io_end = io_end;