The patch titled
Subject: block/bio.c: update bi_iter.bi_size before recounting segments
has been removed from the -mm tree. Its filename was
bio-modify-__bio_add_page-to-accept-pages-that-dont-start-a-new-segment-fix.patch
This patch was dropped because it was folded into bio-modify-__bio_add_page-to-accept-pages-that-dont-start-a-new-segment.patch
------------------------------------------------------
From: Ming Lei <ming.lei@xxxxxxxxxxxxx>
Subject: block/bio.c: update bi_iter.bi_size before recounting segments
The patch of "bio: modify __bio_add_page() to accept pages that
don't start a new segment" changes the way for adding one page
to bio:
- previously by adding page after checking successfully
- now by trying to add page and recover if it fails
Unfortunately the patch forgets to update bio->bi_iter.bi_size
before trying to add page, then the last vector for holding
the added page may not be covered if recouning segments is needed,
so bio->bi_phys_segments may become not consistent with the
actual bio page buffers after the page is added successfully
to the bio(after bi_iter.bi_size is added by 'len')
Suppose the page in the last vector can't be merged to bio, tragedy
will happen when __bio_add_page() is called to add another page:
- blk_recount_segments() is called and the actual segments get
figured out correctly
- the actual segments may become queue_max_segments(q) plus one
in failure path
- driver will find the segment count is too big to handle.
The patch fixes the virtio-blk oops bug reported from Jet Chen in
below link:
http://marc.info/?l=linux-kernel&m=140113053817095&w=2
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
Reported-by: Jet Chen <jet.chen@xxxxxxxxx>
Tested-by: Jet Chen <jet.chen@xxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Maurizio Lombardi <mlombard@xxxxxxxxxx>
Tested-by: Dongsu Park <dongsu.park@xxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Kent Overstreet <kmo@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
block/bio.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff -puN block/bio.c~bio-modify-__bio_add_page-to-accept-pages-that-dont-start-a-new-segment-fix block/bio.c
--- a/block/bio.c~bio-modify-__bio_add_page-to-accept-pages-that-dont-start-a-new-segment-fix
+++ a/block/bio.c
@@ -744,6 +744,7 @@ static int __bio_add_page(struct request
}
}
+ bio->bi_iter.bi_size += len;
goto done;
}
}
@@ -761,6 +762,7 @@ static int __bio_add_page(struct request
bvec->bv_offset = offset;
bio->bi_vcnt++;
bio->bi_phys_segments++;
+ bio->bi_iter.bi_size += len;
/*
* Perform a recount if the number of segments is greater
@@ -802,7 +804,6 @@ static int __bio_add_page(struct request
bio->bi_flags &= ~(1 << BIO_SEG_VALID);
done:
- bio->bi_iter.bi_size += len;
return len;
failed:
@@ -810,6 +811,7 @@ static int __bio_add_page(struct request
bvec->bv_len = 0;
bvec->bv_offset = 0;
bio->bi_vcnt--;
+ bio->bi_iter.bi_size -= len;
blk_recount_segments(q, bio);
return 0;
}
_
Patches currently in -mm which might be from ming.lei@xxxxxxxxxxxxx are
block-bioc-update-bi_iterbi_size-before-recounting-segments.patch
bio-modify-__bio_add_page-to-accept-pages-that-dont-start-a-new-segment.patch
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