NVMe: IOCTL path RCU protect queue access

This adds rcu protected access to a queue in the nvme IOCTL path
to fix potential races between a surprise removal and queue usage in
nvme_submit_sync_cmd. The fix holds the rcu_read_lock() here to prevent
the nvme_queue from freeing while this path is executing so it can't
sleep, and so this path will no longer wait for a available command
id should they all be in use at the time a passthrough IOCTL request
is received.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>

1 files changed, 4 insertions, 27 deletions

diff --git a/drivers/block/nvme-scsi.c b/drivers/block/nvme-scsi.c
index 4a0ceb64e269..e157e85bb5d7 100644
--- a/drivers/block/nvme-scsi.c
+++ b/drivers/block/nvme-scsi.c
@@ -2033,7 +2033,6 @@ static int nvme_trans_do_nvme_io(struct nvme_ns *ns, struct sg_io_hdr *hdr,
         int res = SNTI_TRANSLATION_SUCCESS;
         int nvme_sc;
         struct nvme_dev *dev = ns->dev;
-        struct nvme_queue *nvmeq;
         u32 num_cmds;
         struct nvme_iod *iod;
         u64 unit_len;
@@ -2106,18 +2105,7 @@ static int nvme_trans_do_nvme_io(struct nvme_ns *ns, struct sg_io_hdr *hdr,
 
                 nvme_offset += unit_num_blocks;
 
-                nvmeq = get_nvmeq(dev);
-                /*
-                 * Since nvme_submit_sync_cmd sleeps, we can't keep
-                 * preemption disabled.  We may be preempted at any
-                 * point, and be rescheduled to a different CPU.  That
-                 * will cause cacheline bouncing, but no additional
-                 * races since q_lock already protects against other
-                 * CPUs.
-                 */
-                put_nvmeq(nvmeq);
-                nvme_sc = nvme_submit_sync_cmd(nvmeq, &c, NULL,
-                                                NVME_IO_TIMEOUT);
+                nvme_sc = nvme_submit_io_cmd(dev, &c, NULL);
                 if (nvme_sc != NVME_SC_SUCCESS) {
                         nvme_unmap_user_pages(dev,
                                 (is_write) ? DMA_TO_DEVICE : DMA_FROM_DEVICE,
@@ -2644,7 +2632,6 @@ static int nvme_trans_start_stop(struct nvme_ns *ns, struct sg_io_hdr *hdr,
 {
         int res = SNTI_TRANSLATION_SUCCESS;
         int nvme_sc;
-        struct nvme_queue *nvmeq;
         struct nvme_command c;
         u8 immed, pcmod, pc, no_flush, start;
 
@@ -2671,10 +2658,7 @@ static int nvme_trans_start_stop(struct nvme_ns *ns, struct sg_io_hdr *hdr,
                         c.common.opcode = nvme_cmd_flush;
                         c.common.nsid = cpu_to_le32(ns->ns_id);
 
-                        nvmeq = get_nvmeq(ns->dev);
-                        put_nvmeq(nvmeq);
-                        nvme_sc = nvme_submit_sync_cmd(nvmeq, &c, NULL, NVME_IO_TIMEOUT);
-
+                        nvme_sc = nvme_submit_io_cmd(ns->dev, &c, NULL);
                         res = nvme_trans_status_code(hdr, nvme_sc);
                         if (res)
                                 goto out;
@@ -2697,15 +2681,12 @@ static int nvme_trans_synchronize_cache(struct nvme_ns *ns,
         int res = SNTI_TRANSLATION_SUCCESS;
         int nvme_sc;
         struct nvme_command c;
-        struct nvme_queue *nvmeq;
 
         memset(&c, 0, sizeof(c));
         c.common.opcode = nvme_cmd_flush;
         c.common.nsid = cpu_to_le32(ns->ns_id);
 
-        nvmeq = get_nvmeq(ns->dev);
-        put_nvmeq(nvmeq);
-        nvme_sc = nvme_submit_sync_cmd(nvmeq, &c, NULL, NVME_IO_TIMEOUT);
+        nvme_sc = nvme_submit_io_cmd(ns->dev, &c, NULL);
 
         res = nvme_trans_status_code(hdr, nvme_sc);
         if (res)
@@ -2872,7 +2853,6 @@ static int nvme_trans_unmap(struct nvme_ns *ns, struct sg_io_hdr *hdr,
         struct nvme_dev *dev = ns->dev;
         struct scsi_unmap_parm_list *plist;
         struct nvme_dsm_range *range;
-        struct nvme_queue *nvmeq;
         struct nvme_command c;
         int i, nvme_sc, res = -ENOMEM;
         u16 ndesc, list_len;
@@ -2914,10 +2894,7 @@ static int nvme_trans_unmap(struct nvme_ns *ns, struct sg_io_hdr *hdr,
         c.dsm.nr = cpu_to_le32(ndesc - 1);
         c.dsm.attributes = cpu_to_le32(NVME_DSMGMT_AD);
 
-        nvmeq = get_nvmeq(dev);
-        put_nvmeq(nvmeq);
-
-        nvme_sc = nvme_submit_sync_cmd(nvmeq, &c, NULL, NVME_IO_TIMEOUT);
+        nvme_sc = nvme_submit_io_cmd(dev, &c, NULL);
         res = nvme_trans_status_code(hdr, nvme_sc);
 
         dma_free_coherent(&dev->pci_dev->dev, ndesc * sizeof(*range),