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Subject[PATCH 024 of 35] Allow request bio list not to end with NULL

If we are going to share a bio between requests, then the
last bio in a list may not point to NULL, but may point to
the next bio in a different list.
So instead of testing if ->bi_next is NULL, test if the bio
matches rq->biotail.

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
./block/ll_rw_blk.c | 8 ++++----
./drivers/block/cciss.c | 16 +++++++++-------
./drivers/block/cpqarray.c | 18 ++++++++----------
./include/linux/blkdev.h | 5 +++--
4 files changed, 24 insertions(+), 23 deletions(-)
diff .prev/block/ll_rw_blk.c ./block/ll_rw_blk.c
--- .prev/block/ll_rw_blk.c 2007-07-31 11:21:07.000000000 +1000
+++ ./block/ll_rw_blk.c 2007-07-31 11:21:14.000000000 +1000
@@ -1196,13 +1196,10 @@ EXPORT_SYMBOL(blk_dump_rq_flags);
void blk_recount_segments(struct request_queue *q, struct bio *bio)
{
struct request rq;
- struct bio *nxt = bio->bi_next;
rq.q = q;
rq.bio = rq.biotail = bio;
rq.first_offset = 0;
- bio->bi_next = NULL;
blk_recalc_rq_segments(&rq);
- bio->bi_next = nxt;
bio->bi_phys_segments = rq.nr_phys_segments;
bio->bi_hw_segments = rq.nr_hw_segments;
bio->bi_flags |= (1 << BIO_SEG_VALID);
@@ -3416,7 +3413,10 @@ static int __end_that_request_first(stru
int nbytes;

if (nr_bytes >= bio->bi_size) {
- req->bio = bio->bi_next;
+ if (req->bio == req->biotail)
+ req->bio = NULL;
+ else
+ req->bio = bio->bi_next;
nbytes = bio->bi_size;
if (!ordered_bio_endio(req, bio, error))
bio_endio(bio, error);
diff .prev/drivers/block/cciss.c ./drivers/block/cciss.c
--- .prev/drivers/block/cciss.c 2007-07-31 11:20:51.000000000 +1000
+++ ./drivers/block/cciss.c 2007-07-31 11:21:14.000000000 +1000
@@ -1187,15 +1187,17 @@ static int cciss_ioctl(struct inode *ino
}
}

-static inline void complete_buffers(struct bio *bio, int status)
+static inline void complete_buffers(struct request *req, int status)
{
- while (bio) {
- struct bio *xbh = bio->bi_next;
- int nr_sectors = bio_sectors(bio);
+ while (req->bio) {
+ struct bio *bio = req->bio;
+
+ if (bio == req->biotail)
+ req->bio = NULL;
+ else
+ req->bio = bio->bi_next;

- bio->bi_next = NULL;
bio_endio(bio, status ? 0 : -EIO);
- bio = xbh;
}
}

@@ -1264,7 +1266,7 @@ static void cciss_softirq_done(struct re
pci_unmap_page(h->pdev, temp64.val, cmd->SG[i].Len, ddir);
}

- complete_buffers(rq->bio, (rq->errors == 0));
+ complete_buffers(rq, (rq->errors == 0));

if (blk_fs_request(rq)) {
const int rw = rq_data_dir(rq);
diff .prev/drivers/block/cpqarray.c ./drivers/block/cpqarray.c
--- .prev/drivers/block/cpqarray.c 2007-07-31 11:20:51.000000000 +1000
+++ ./drivers/block/cpqarray.c 2007-07-31 11:21:14.000000000 +1000
@@ -166,7 +166,6 @@ static void start_io(ctlr_info_t *h);

static inline void addQ(cmdlist_t **Qptr, cmdlist_t *c);
static inline cmdlist_t *removeQ(cmdlist_t **Qptr, cmdlist_t *c);
-static inline void complete_buffers(struct bio *bio, int ok);
static inline void complete_command(cmdlist_t *cmd, int timeout);

static irqreturn_t do_ida_intr(int irq, void *dev_id);
@@ -979,18 +978,17 @@ static void start_io(ctlr_info_t *h)
}
}

-static inline void complete_buffers(struct bio *bio, int ok)
+static inline void complete_buffers(struct request *req, int ok)
{
- struct bio *xbh;
- while(bio) {
- int nr_sectors = bio_sectors(bio);
+ while (req->bio) {
+ struct bio *bio = req->bio;

- xbh = bio->bi_next;
- bio->bi_next = NULL;
+ if (bio == req->biotail)
+ req->bio = NULL;
+ else
+ req->bio = bio->bi_next;

bio_endio(bio, ok ? 0 : -EIO);
-
- bio = xbh;
}
}
/*
@@ -1030,7 +1028,7 @@ static inline void complete_command(cmdl
pci_unmap_page(hba[cmd->ctlr]->pci_dev, cmd->req.sg[i].addr,
cmd->req.sg[i].size, ddir);

- complete_buffers(rq->bio, ok);
+ complete_buffers(rq, ok);

if (blk_fs_request(rq)) {
const int rw = rq_data_dir(rq);
diff .prev/include/linux/blkdev.h ./include/linux/blkdev.h
--- .prev/include/linux/blkdev.h 2007-07-31 11:21:07.000000000 +1000
+++ ./include/linux/blkdev.h 2007-07-31 11:21:14.000000000 +1000
@@ -660,12 +660,13 @@ struct req_iterator {
};
#define rq_for_each_segment(rq, _iter, bvec) \
for (_iter.bio = (rq)->bio, _iter.offset = (rq)->first_offset; \
- _iter.bio; \
+ _iter.bio && _iter.bio != rq->biotail->bi_next; \
_iter.bio = _iter.bio->bi_next, _iter.offset = 0) \
bio_for_each_segment_offset(bvec, _iter.bio, _iter.i, \
_iter.offset)

-#define rq_iter_last(rq, _iter) (_iter.bio->bi_next == NULL && \
+#define rq_iter_last(rq, _iter) ((_iter.bio->bi_next == NULL || \
+ _iter.bio == rq->biotail) && \
_iter.i.i == _iter.bio->bi_vcnt - 1)

extern int blk_register_queue(struct gendisk *disk);
-
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