From: Andrew Morton <akpm@osdl.org>
To: Peter Osterlund <petero2@telia.com>
Cc: axboe@suse.de, packet-writing@suse.com, linux-kernel@vger.kernel.org
Subject: Re: ext2 on a CD-RW
Date: Thu, 1 Jan 2004 16:24:27 -0800 [thread overview]
Message-ID: <20040101162427.4c6c020b.akpm@osdl.org> (raw)
In-Reply-To: <Pine.LNX.4.44.0401020022060.2407-100000@telia.com>
Peter Osterlund <petero2@telia.com> wrote:
>
> If I create an ext2 filesystem
> with 2kb blocksize, I hit a bug when I try to write some large files to
> the filesystem. The problem is that the code in mpage_writepage() fails if
> a page is mapped to disk across a packet boundary. In that case, the
> bio_add_page() call at line 543 in mpage.c can fail even if the bio was
> previously empty. The code then passes an empty bio to submit_bio(), which
> triggers a bug at line 2303 in ll_rw_blk.c. This patch seems to fix the
> problem.
>
> --- linux/fs/mpage.c.old 2004-01-02 00:26:19.000000000 +0100
> +++ linux/fs/mpage.c 2004-01-02 00:26:50.000000000 +0100
> @@ -541,6 +541,11 @@
>
> length = first_unmapped << blkbits;
> if (bio_add_page(bio, page, length, 0) < length) {
> + if (!bio->bi_size) {
> + bio_put(bio);
> + bio = NULL;
> + goto confused;
> + }
> bio = mpage_bio_submit(WRITE, bio);
> goto alloc_new;
> }
Confused. We initially have an empty BIO, and we run bio_add_page()
against it, adding one page.
How can that bio_add_page() fail to add the page?
Cold you describe the failure a little more please?
> I noted that performance is quite bad with 2kb blocksize. It is a lot
> faster with 4kb blocksize. (2kb blocksize with the udf filesystem is not
> slow, only ext2 seems to have this problem.) Maybe the "confused" case
> (which calls a_ops->writepage()) in mpage_writepage() isn't really meant
> to be fast. Is there a better way to fix this problem?
How much slower is it?
next prev parent reply other threads:[~2004-01-02 0:23 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-01-01 23:47 Peter Osterlund
2004-01-02 0:24 ` Andrew Morton [this message]
2004-01-02 1:30 ` Peter Osterlund
2004-01-02 9:06 ` Arjan van de Ven
2004-01-02 10:09 ` Jens Axboe
2004-01-02 10:51 ` Peter Osterlund
2004-01-02 10:59 ` Jens Axboe
2004-01-02 12:09 ` Peter Osterlund
2004-01-02 12:19 ` Jens Axboe
2004-01-02 13:38 ` Peter Osterlund
2004-01-02 13:59 ` Jens Axboe
2004-01-02 16:12 ` Peter Osterlund
2004-03-29 15:38 ` Peter Osterlund
2004-01-02 10:08 ` Jens Axboe
2004-01-03 19:14 ` Pavel Machek
2004-01-03 20:32 ` Peter Osterlund
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