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Date: Thu, 07 Mar 2013 12:23:13 +0100 From: Jan Vesely <jvesely@...hat.com> To: linux-kernel@...r.kernel.org CC: linux-scsi@...r.kernel.org, linux-fsdevel@...r.kernel.org, Alexander Viro <viro@...iv.linux.org.uk>, Jens Axboe <axboe@...nel.dk> Subject: Re: [PATCH] block: modify __bio_add_page check to accept pages that don't start a new segment Hi Jens, I have added you to cc, I'm not sure who to bug to get this patch merged. thanks, Jan Vesely On Thu 21 Feb 2013 09:30:26 CET, Jan Vesely wrote: > The original behavior was to refuse all pages after the maximum number of > segments has been reached. However, some drivers (like st) craft their buffers > to potentially require exactly max segments and multiple pages in the last > segment. This patch modifies the check to allow pages that can be merged into > the last segment. > > This change fixes EBUSY failures when using large (1mb) tape block size in high > memory fragmentation condition. > > Signed-off-by: Jan Vesely <jvesely@...hat.com> > --- > fs/bio.c | 26 ++++++++++++++++---------- > 1 files changed, 16 insertions(+), 10 deletions(-) > > diff --git a/fs/bio.c b/fs/bio.c > index b96fc6c..02efbd5 100644 > --- a/fs/bio.c > +++ b/fs/bio.c > @@ -500,7 +500,6 @@ static int __bio_add_page(struct request_queue *q, struct > bio *bio, struct page > *page, unsigned int len, unsigned int offset, > unsigned short max_sectors) > { > - int retried_segments = 0; > struct bio_vec *bvec; > > /* > @@ -551,18 +550,12 @@ static int __bio_add_page(struct request_queue *q, > struct bio *bio, struct page > return 0; > > /* > - * we might lose a segment or two here, but rather that than > - * make this too complex. > + * prepare segment count check, reduce segment count if possible > */ > > - while (bio->bi_phys_segments >= queue_max_segments(q)) { > - > - if (retried_segments) > - return 0; > - > - retried_segments = 1; > + if (bio->bi_phys_segments >= queue_max_segments(q)) > blk_recount_segments(q, bio); > - } > + > > /* > * setup the new entry, we might clear it again later if we > @@ -572,6 +565,19 @@ static int __bio_add_page(struct request_queue *q, struct > bio *bio, struct page > bvec->bv_page = page; > bvec->bv_len = len; > bvec->bv_offset = offset; > + > + /* > + * the other part of the segment count check, allow mergeable pages > + */ > + if ((bio->bi_phys_segments > queue_max_segments(q)) || > + ( (bio->bi_phys_segments == queue_max_segments(q)) && > + !BIOVEC_PHYS_MERGEABLE(bvec - 1, bvec))) { > + bvec->bv_page = NULL; > + bvec->bv_len = 0; > + bvec->bv_offset = 0; > + return 0; > + } > + > > /* > * if queue has other restrictions (eg varying max sector size -- Jan Vesely <jvesely@...hat.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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