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142 lines
5.0 KiB
142 lines
5.0 KiB
From 6878c32e5cc0e40980abe51d1f02fb453e27493e Mon Sep 17 00:00:00 2001
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From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Date: Fri, 25 May 2012 17:34:51 -0400
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Subject: [PATCH 3/3] xen/blkfront: Add WARN to deal with misbehaving
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backends.
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Part of the ring structure is the 'id' field which is under
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control of the frontend. The frontend stamps it with "some"
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value (this some in this implementation being a value less
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than BLK_RING_SIZE), and when it gets a response expects
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said value to be in the response structure. We have a check
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for the id field when spolling new requests but not when
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de-spolling responses.
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We also add an extra check in add_id_to_freelist to make
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sure that the 'struct request' was not NULL - as we cannot
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pass a NULL to __blk_end_request_all, otherwise that crashes
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(and all the operations that the response is dealing with
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end up with __blk_end_request_all).
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Lastly we also print the name of the operation that failed.
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[v1: s/BUG/WARN/ suggested by Stefano]
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[v2: Add extra check in add_id_to_freelist]
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[v3: Redid op_name per Jan's suggestion]
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[v4: add const * and add WARN on failure returns]
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Acked-by: Jan Beulich <jbeulich@suse.com>
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Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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---
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drivers/block/xen-blkfront.c | 58 +++++++++++++++++++++++++++++++++--------
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1 files changed, 46 insertions(+), 12 deletions(-)
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diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
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index 60eed4b..e4fb337 100644
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--- a/drivers/block/xen-blkfront.c
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+++ b/drivers/block/xen-blkfront.c
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@@ -141,14 +141,36 @@ static int get_id_from_freelist(struct blkfront_info *info)
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return free;
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}
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-static void add_id_to_freelist(struct blkfront_info *info,
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+static int add_id_to_freelist(struct blkfront_info *info,
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unsigned long id)
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{
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+ if (info->shadow[id].req.u.rw.id != id)
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+ return -EINVAL;
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+ if (info->shadow[id].request == NULL)
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+ return -EINVAL;
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info->shadow[id].req.u.rw.id = info->shadow_free;
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info->shadow[id].request = NULL;
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info->shadow_free = id;
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+ return 0;
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}
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+static const char *op_name(int op)
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+{
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+ static const char *const names[] = {
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+ [BLKIF_OP_READ] = "read",
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+ [BLKIF_OP_WRITE] = "write",
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+ [BLKIF_OP_WRITE_BARRIER] = "barrier",
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+ [BLKIF_OP_FLUSH_DISKCACHE] = "flush",
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+ [BLKIF_OP_DISCARD] = "discard" };
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+
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+ if (op < 0 || op >= ARRAY_SIZE(names))
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+ return "unknown";
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+
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+ if (!names[op])
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+ return "reserved";
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+
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+ return names[op];
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+}
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static int xlbd_reserve_minors(unsigned int minor, unsigned int nr)
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{
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unsigned int end = minor + nr;
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@@ -746,20 +768,36 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
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bret = RING_GET_RESPONSE(&info->ring, i);
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id = bret->id;
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+ /*
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+ * The backend has messed up and given us an id that we would
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+ * never have given to it (we stamp it up to BLK_RING_SIZE -
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+ * look in get_id_from_freelist.
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+ */
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+ if (id >= BLK_RING_SIZE) {
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+ WARN(1, "%s: response to %s has incorrect id (%ld)\n",
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+ info->gd->disk_name, op_name(bret->operation), id);
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+ /* We can't safely get the 'struct request' as
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+ * the id is busted. */
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+ continue;
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+ }
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req = info->shadow[id].request;
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if (bret->operation != BLKIF_OP_DISCARD)
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blkif_completion(&info->shadow[id]);
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- add_id_to_freelist(info, id);
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+ if (add_id_to_freelist(info, id)) {
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+ WARN(1, "%s: response to %s (id %ld) couldn't be recycled!\n",
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+ info->gd->disk_name, op_name(bret->operation), id);
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+ continue;
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+ }
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error = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO;
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switch (bret->operation) {
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case BLKIF_OP_DISCARD:
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if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
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struct request_queue *rq = info->rq;
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- printk(KERN_WARNING "blkfront: %s: discard op failed\n",
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- info->gd->disk_name);
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+ printk(KERN_WARNING "blkfront: %s: %s op failed\n",
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+ info->gd->disk_name, op_name(bret->operation));
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error = -EOPNOTSUPP;
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info->feature_discard = 0;
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info->feature_secdiscard = 0;
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@@ -771,18 +809,14 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
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case BLKIF_OP_FLUSH_DISKCACHE:
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case BLKIF_OP_WRITE_BARRIER:
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if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
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- printk(KERN_WARNING "blkfront: %s: write %s op failed\n",
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- info->flush_op == BLKIF_OP_WRITE_BARRIER ?
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- "barrier" : "flush disk cache",
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- info->gd->disk_name);
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+ printk(KERN_WARNING "blkfront: %s: %s op failed\n",
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+ info->gd->disk_name, op_name(bret->operation));
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error = -EOPNOTSUPP;
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}
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if (unlikely(bret->status == BLKIF_RSP_ERROR &&
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info->shadow[id].req.u.rw.nr_segments == 0)) {
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- printk(KERN_WARNING "blkfront: %s: empty write %s op failed\n",
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- info->flush_op == BLKIF_OP_WRITE_BARRIER ?
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- "barrier" : "flush disk cache",
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- info->gd->disk_name);
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+ printk(KERN_WARNING "blkfront: %s: empty %s op failed\n",
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+ info->gd->disk_name, op_name(bret->operation));
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error = -EOPNOTSUPP;
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}
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if (unlikely(error)) {
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--
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1.7.4.4
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