Commit 99451879 authored Sep 18, 2015 by Ming Lei Committed by Jens Axboe Sep 17, 2015

block: fix bounce_end_io



When bio bounce is involved, one new bio and its biovecs are
cloned from the comming bio, which can be one fast-cloned bio
from upper layer(such as dm).

So it is obviously wrong to assume the start index of the coming(
original) bio's io vector is zero, which can be any value between
0 and (bi_max_vecs - 1), especially in case of bio split.

This patch fixes Fedora's booting oops on i386, often with the
following kernel log together:

> [    9.026738] systemd[1]: Switching root.
> [    9.036467] systemd-journald[149]: Received SIGTERM from PID 1
> (systemd).
> [    9.082262] BUG: Bad page state in process kworker/u5:1  pfn:372ac
> [    9.083989] page:f3d32ae0 count:0 mapcount:0 mapping:f2252178
> index:0x16a
> [    9.085755] flags: 0x40020021(locked|lru|mappedtodisk)
> [    9.087284] page dumped because: page still charged to cgroup
> [    9.088772] bad because of flags:
> [    9.089731] flags: 0x21(locked|lru)
> [    9.090818] page->mem_cgroup:f2c3e400

Reported-by: Josh Boyer <jwboyer@fedoraproject.org>
Tested-by: Adam Williamson <awilliam@redhat.com>
Cc: Ming Lin <mlin@kernel.org>
Cc: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

parent 52cc6eea

block/bounce.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -128,12 +128,14 @@ static void bounce_end_io(struct bio bio, mempool_t pool)
		struct bio *bio_orig = bio->bi_private;
		struct bio_vec bvec, org_vec;
		int i;
		int start = bio_orig->bi_iter.bi_idx;

		/*
		* free up bounce indirect pages used
		*/
		bio_for_each_segment_all(bvec, bio, i) {
		org_vec = bio_orig->bi_io_vec + i;
		org_vec = bio_orig->bi_io_vec + i + start;

		if (bvec->bv_page == org_vec->bv_page)
		continue;

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