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Commit 5df521b1 authored by Alex Elder's avatar Alex Elder Committed by Sage Weil
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libceph: page offset must be less than page size 

Currently ceph_msg_data_pages_advance() allows the page offset value
to be PAGE_SIZE, apparently assuming ceph_msg_data_pages_next() will
treat it as 0.  But that doesn't happen, and the result led to a
helpful assertion failure.

Change ceph_msg_data_pages_advance() to truncate the offset to 0
before returning if it reaches PAGE_SIZE.

Make a few other minor adjustments in this area (comments and a
better assertion) while modifying it.

This resolves a second issue described in:
    http://tracker.ceph.com/issues/4598



Signed-off-by: default avatarAlex Elder <elder@inktank.com>
Reviewed-by: default avatarSage Weil <sage@inktank.com>
parent 1190bf06

net/ceph/messenger.c

+7 −7
Original line number Diff line number Diff line
@@ -766,8 +766,8 @@ static struct page *ceph_msg_data_bio_next(struct ceph_msg_data *data, 
		*length = cursor->resid;

	else

		*length = (size_t) (bio_vec->bv_len - cursor->vector_offset);

	BUG_ON(*length > PAGE_SIZE);

	BUG_ON(*length > cursor->resid);

	BUG_ON(*page_offset + *length > PAGE_SIZE);



	return bio_vec->bv_page;

}
@@ -876,14 +876,13 @@ static bool ceph_msg_data_pages_advance(struct ceph_msg_data *data, 
	/* Advance the cursor page offset */



	cursor->resid -= bytes;

	cursor->page_offset += bytes;

	if (!bytes || cursor->page_offset & ~PAGE_MASK)

	cursor->page_offset = (cursor->page_offset + bytes) & ~PAGE_MASK;

	if (!bytes || cursor->page_offset)

		return false;	/* more bytes to process in the current page */



	/* Move on to the next page */

	/* Move on to the next page; offset is already at 0 */



	BUG_ON(cursor->page_index >= cursor->page_count);

	cursor->page_offset = 0;

	cursor->page_index++;

	cursor->last_piece = cursor->resid <= PAGE_SIZE;
@@ -934,8 +933,9 @@ static struct page *ceph_msg_data_pagelist_next(struct ceph_msg_data *data, 
	BUG_ON(!cursor->page);

	BUG_ON(cursor->offset + cursor->resid != pagelist->length);



	/* offset of first page in pagelist is always 0 */

	*page_offset = cursor->offset & ~PAGE_MASK;

	if (cursor->last_piece) /* pagelist offset is always 0 */

	if (cursor->last_piece)

		*length = cursor->resid;

	else

		*length = PAGE_SIZE - *page_offset;
@@ -961,7 +961,7 @@ static bool ceph_msg_data_pagelist_advance(struct ceph_msg_data *data, 


	cursor->resid -= bytes;

	cursor->offset += bytes;

	/* pagelist offset is always 0 */

	/* offset of first page in pagelist is always 0 */

	if (!bytes || cursor->offset & ~PAGE_MASK)

		return false;	/* more bytes to process in the current page */