From: Juergen Gross jgross@suse.com
commit 71b66243f9898d0e54296b4e7035fb33cdcb0707 upstream.
In order to avoid problems in case the backend is modifying a response on the ring page while the frontend has already seen it, just read the response into a local buffer in one go and then operate on that buffer only.
Signed-off-by: Juergen Gross jgross@suse.com Reviewed-by: Jan Beulich jbeulich@suse.com Acked-by: Roger Pau Monné roger.pau@citrix.com Link: https://lore.kernel.org/r/20210730103854.12681-2-jgross@suse.com Signed-off-by: Juergen Gross jgross@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/block/xen-blkfront.c | 35 ++++++++++++++++++----------------- 1 file changed, 18 insertions(+), 17 deletions(-)
--- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -1296,7 +1296,7 @@ static void blkif_completion(struct blk_ static irqreturn_t blkif_interrupt(int irq, void *dev_id) { struct request *req; - struct blkif_response *bret; + struct blkif_response bret; RING_IDX i, rp; unsigned long flags; struct blkfront_info *info = (struct blkfront_info *)dev_id; @@ -1316,8 +1316,9 @@ static irqreturn_t blkif_interrupt(int i for (i = info->ring.rsp_cons; i != rp; i++) { unsigned long id;
- bret = RING_GET_RESPONSE(&info->ring, i); - id = bret->id; + RING_COPY_RESPONSE(&info->ring, i, &bret); + id = bret.id; + /* * The backend has messed up and given us an id that we would * never have given to it (we stamp it up to BLK_RING_SIZE - @@ -1325,29 +1326,29 @@ static irqreturn_t blkif_interrupt(int i */ if (id >= BLK_RING_SIZE(info)) { WARN(1, "%s: response to %s has incorrect id (%ld)\n", - info->gd->disk_name, op_name(bret->operation), id); + info->gd->disk_name, op_name(bret.operation), id); /* We can't safely get the 'struct request' as * the id is busted. */ continue; } req = info->shadow[id].request;
- if (bret->operation != BLKIF_OP_DISCARD) - blkif_completion(&info->shadow[id], info, bret); + if (bret.operation != BLKIF_OP_DISCARD) + blkif_completion(&info->shadow[id], info, &bret);
if (add_id_to_freelist(info, id)) { WARN(1, "%s: response to %s (id %ld) couldn't be recycled!\n", - info->gd->disk_name, op_name(bret->operation), id); + info->gd->disk_name, op_name(bret.operation), id); continue; }
- error = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO; - switch (bret->operation) { + error = (bret.status == BLKIF_RSP_OKAY) ? 0 : -EIO; + switch (bret.operation) { case BLKIF_OP_DISCARD: - if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) { + if (unlikely(bret.status == BLKIF_RSP_EOPNOTSUPP)) { struct request_queue *rq = info->rq; printk(KERN_WARNING "blkfront: %s: %s op failed\n", - info->gd->disk_name, op_name(bret->operation)); + info->gd->disk_name, op_name(bret.operation)); error = -EOPNOTSUPP; info->feature_discard = 0; info->feature_secdiscard = 0; @@ -1358,15 +1359,15 @@ static irqreturn_t blkif_interrupt(int i break; case BLKIF_OP_FLUSH_DISKCACHE: case BLKIF_OP_WRITE_BARRIER: - if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) { + if (unlikely(bret.status == BLKIF_RSP_EOPNOTSUPP)) { printk(KERN_WARNING "blkfront: %s: %s op failed\n", - info->gd->disk_name, op_name(bret->operation)); + info->gd->disk_name, op_name(bret.operation)); error = -EOPNOTSUPP; } - if (unlikely(bret->status == BLKIF_RSP_ERROR && + if (unlikely(bret.status == BLKIF_RSP_ERROR && info->shadow[id].req.u.rw.nr_segments == 0)) { printk(KERN_WARNING "blkfront: %s: empty %s op failed\n", - info->gd->disk_name, op_name(bret->operation)); + info->gd->disk_name, op_name(bret.operation)); error = -EOPNOTSUPP; } if (unlikely(error)) { @@ -1378,9 +1379,9 @@ static irqreturn_t blkif_interrupt(int i /* fall through */ case BLKIF_OP_READ: case BLKIF_OP_WRITE: - if (unlikely(bret->status != BLKIF_RSP_OKAY)) + if (unlikely(bret.status != BLKIF_RSP_OKAY)) dev_dbg(&info->xbdev->dev, "Bad return from blkdev data " - "request: %x\n", bret->status); + "request: %x\n", bret.status);
blk_mq_complete_request(req, error); break;