Commit 5ce765a5 authored Sep 21, 2012 by Alex Elder Committed by Sage Weil Sep 21, 2012

libceph: only kunmap kmapped pages



In write_partial_msg_pages(), pages need to be kmapped in order to
perform a CRC-32c calculation on them.  As an artifact of the way
this code used to be structured, the kunmap() call was separated
from the kmap() call and both were done conditionally.  But the
conditions under which the kmap() and kunmap() calls were made
differed, so there was a chance a kunmap() call would be done on a
page that had not been mapped.

The symptom of this was tripping a BUG() in kunmap_high() when
pkmap_count[nr] became 0.

Reported-by: Bryan K. Wright <bryan@virginia.edu>
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

parent 340c7a2b

net/ceph/messenger.c

+1 −4

Original line number	Diff line number	Diff line
		@@ -1073,16 +1073,13 @@ static int write_partial_msg_pages(struct ceph_connection *con)
		BUG_ON(kaddr == NULL);
		base = kaddr + con->out_msg_pos.page_pos + bio_offset;
		crc = crc32c(crc, base, len);
		kunmap(page);
		msg->footer.data_crc = cpu_to_le32(crc);
		con->out_msg_pos.did_page_crc = true;
		}
		ret = ceph_tcp_sendpage(con->sock, page,
		con->out_msg_pos.page_pos + bio_offset,
		len, 1);

		if (do_datacrc)
		kunmap(page);

		if (ret <= 0)
		goto out;

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