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>
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@ -1073,16 +1073,13 @@ static int write_partial_msg_pages(struct ceph_connection *con)
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BUG_ON(kaddr == NULL);
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base = kaddr + con->out_msg_pos.page_pos + bio_offset;
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crc = crc32c(crc, base, len);
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kunmap(page);
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msg->footer.data_crc = cpu_to_le32(crc);
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con->out_msg_pos.did_page_crc = true;
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}
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ret = ceph_tcp_sendpage(con->sock, page,
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con->out_msg_pos.page_pos + bio_offset,
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len, 1);
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if (do_datacrc)
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kunmap(page);
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if (ret <= 0)
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goto out;
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