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rbd: fix I/O error propagation for reads 

When a request returns an error, the driver needs to report the entire
extent of the request as completed.  Writes already did this, since
they always set xferred = length, but reads were skipping that step if
an error other than -ENOENT occurred.  Instead, rbd would end up
passing 0 xferred to blk_end_request(), which would always report
needing more data.  This resulted in an assert failing when more data
was required by the block layer, but all the object requests were
done:

[ 1868.719077] rbd: obj_request read result -108 xferred 0
[ 1868.719077]
[ 1868.719518] end_request: I/O error, dev rbd1, sector 0
[ 1868.719739]
[ 1868.719739] Assertion failure in rbd_img_obj_callback() at line 1736:
[ 1868.719739]
[ 1868.719739]   rbd_assert(more ^ (which == img_request->obj_request_count));

Without this assert, reads that hit errors would hang forever, since
the block layer considered them incomplete.

Fixes: http://tracker.ceph.com/issues/5647
CC: stable@vger.kernel.org  # v3.10
Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
Reviewed-by: Alex Elder <alex.elder@linaro.org>
This commit is contained in:
Josh Durgin 2013-08-26 17:55:38 -07:00 committed by Sage Weil
parent 7d6e1f5461
commit 17c1cc1d92
1 changed files with 7 additions and 7 deletions
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14
drivers/block/rbd.c
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@ -1557,11 +1557,12 @@ rbd_img_obj_request_read_callback(struct rbd_obj_request *obj_request)
obj_request, obj_request->img_request, obj_request->result,
xferred, length);
/*
* ENOENT means a hole in the image. We zero-fill the
* entire length of the request. A short read also implies
* zero-fill to the end of the request. Either way we
* update the xferred count to indicate the whole request
* was satisfied.
* ENOENT means a hole in the image. We zero-fill the entire
* length of the request. A short read also implies zero-fill
* to the end of the request. An error requires the whole
* length of the request to be reported finished with an error
* to the block layer. In each case we update the xferred
* count to indicate the whole request was satisfied.
*/
rbd_assert(obj_request->type != OBJ_REQUEST_NODATA);
if (obj_request->result == -ENOENT) {
@ -1570,14 +1571,13 @@ rbd_img_obj_request_read_callback(struct rbd_obj_request *obj_request)
else
zero_pages(obj_request->pages, 0, length);
obj_request->result = 0;
obj_request->xferred = length;
} else if (xferred < length && !obj_request->result) {
if (obj_request->type == OBJ_REQUEST_BIO)
zero_bio_chain(obj_request->bio_list, xferred);
else
zero_pages(obj_request->pages, xferred, length);
obj_request->xferred = length;
}
obj_request->xferred = length;
obj_request_done_set(obj_request);
}