Create the ability to drain ioctls by wrapping the ioctl handler
call in a read semaphore and then implementing a small routine that
obtains the write semaphore, effectively creating a wait point for
all currently executing ioctls.
Signed-off-by: Matthew R. Ochs <mrochs@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Manoj N. Kumar <manoj@xxxxxxxxxxxxxxxxxx>
---
drivers/scsi/cxlflash/common.h | 2 +
drivers/scsi/cxlflash/main.c | 18 +++++--
drivers/scsi/cxlflash/superpipe.c | 104 +++++++++++++++++++++++---------------
3 files changed, 81 insertions(+), 43 deletions(-)
diff --git a/drivers/scsi/cxlflash/common.h b/drivers/scsi/cxlflash/common.h
index 1c56037..1abe4e0 100644
--- a/drivers/scsi/cxlflash/common.h
+++ b/drivers/scsi/cxlflash/common.h
@@ -16,6 +16,7 @@
#define _CXLFLASH_COMMON_H
#include <linux/list.h>
+#include <linux/rwsem.h>
#include <linux/types.h>
#include <scsi/scsi.h>
#include <scsi/scsi_device.h>
@@ -110,6 +111,7 @@ struct cxlflash_cfg {
atomic_t recovery_threads;
struct mutex ctx_recovery_mutex;
struct mutex ctx_tbl_list_mutex;
+ struct rw_semaphore ioctl_rwsem;
struct ctx_info *ctx_tbl[MAX_CONTEXT];
struct list_head ctx_err_recovery; /* contexts w/ recovery pending */
struct file_operations cxl_fops;
diff --git a/drivers/scsi/cxlflash/main.c b/drivers/scsi/cxlflash/main.c
index 3e3ccf1..6e85c77 100644
--- a/drivers/scsi/cxlflash/main.c
+++ b/drivers/scsi/cxlflash/main.c
@@ -2311,6 +2311,7 @@ static int cxlflash_probe(struct pci_dev *pdev,
cfg->lr_port = -1;
mutex_init(&cfg->ctx_tbl_list_mutex);
mutex_init(&cfg->ctx_recovery_mutex);
+ init_rwsem(&cfg->ioctl_rwsem);
INIT_LIST_HEAD(&cfg->ctx_err_recovery);
INIT_LIST_HEAD(&cfg->lluns);
@@ -2365,6 +2366,19 @@ out_remove:
}
/**
+ * drain_ioctls() - wait until all currently executing ioctls have completed
+ * @cfg: Internal structure associated with the host.
+ *
+ * Obtain write access to read/write semaphore that wraps ioctl
+ * handling to 'drain' ioctls currently executing.
+ */
+static void drain_ioctls(struct cxlflash_cfg *cfg)
+{
+ down_write(&cfg->ioctl_rwsem);
+ up_write(&cfg->ioctl_rwsem);
+}
+
+/**
* cxlflash_pci_error_detected() - called when a PCI error is detected
* @pdev: PCI device struct.
* @state: PCI channel state.
@@ -2383,16 +2397,14 @@ static pci_ers_result_t cxlflash_pci_error_detected(struct pci_dev *pdev,
switch (state) {
case pci_channel_io_frozen:
cfg->state = STATE_LIMBO;
-
- /* Turn off legacy I/O */
scsi_block_requests(cfg->host);
+ drain_ioctls(cfg);
rc = cxlflash_mark_contexts_error(cfg);
if (unlikely(rc))
dev_err(dev, "%s: Failed to mark user contexts!(%d)\n",
__func__, rc);
term_mc(cfg, UNDO_START);
stop_afu(cfg);
-
return PCI_ERS_RESULT_NEED_RESET;
case pci_channel_io_perm_failure:
cfg->state = STATE_FAILTERM;
diff --git a/drivers/scsi/cxlflash/superpipe.c b/drivers/scsi/cxlflash/superpipe.c
index cf2a85d..8a18230 100644
--- a/drivers/scsi/cxlflash/superpipe.c
+++ b/drivers/scsi/cxlflash/superpipe.c
@@ -1214,6 +1214,48 @@ static const struct file_operations null_fops = {
};
/**
+ * check_state() - checks and responds to the current adapter state
+ * @cfg: Internal structure associated with the host.
+ * @ioctl: Indicates if on an ioctl thread.
+ *
+ * This routine can block and should only be used on process context.
+ * When blocking on an ioctl thread, the ioctl read semaphore should be
+ * let up to allow for draining actively running ioctls. Also note that
+ * when waking up from waiting in reset, the state is unknown and must
+ * be checked again before proceeding.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static int check_state(struct cxlflash_cfg *cfg, bool ioctl)
+{
+ struct device *dev = &cfg->dev->dev;
+ int rc = 0;
+
+retry:
+ switch (cfg->state) {
+ case STATE_LIMBO:
+ dev_dbg(dev, "%s: Limbo state, going to wait...\n", __func__);
+ if (ioctl)
+ up_read(&cfg->ioctl_rwsem);
+ rc = wait_event_interruptible(cfg->limbo_waitq,
+ cfg->state != STATE_LIMBO);
+ if (ioctl)
+ down_read(&cfg->ioctl_rwsem);
+ if (unlikely(rc))
+ break;
+ goto retry;
+ case STATE_FAILTERM:
+ dev_dbg(dev, "%s: Failed/Terminating!\n", __func__);
+ rc = -ENODEV;
+ break;
+ default:
+ break;
+ }
+
+ return rc;
+}
+
+/**
* cxlflash_disk_attach() - attach a LUN to a context
* @sdev: SCSI device associated with LUN.
* @attach: Attach ioctl data structure.
@@ -1524,41 +1566,6 @@ err1:
}
/**
- * check_state() - checks and responds to the current adapter state
- * @cfg: Internal structure associated with the host.
- *
- * This routine can block and should only be used on process context.
- * Note that when waking up from waiting in limbo, the state is unknown
- * and must be checked again before proceeding.
- *
- * Return: 0 on success, -errno on failure
- */
-static int check_state(struct cxlflash_cfg *cfg)
-{
- struct device *dev = &cfg->dev->dev;
- int rc = 0;
-
-retry:
- switch (cfg->state) {
- case STATE_LIMBO:
- dev_dbg(dev, "%s: Limbo, going to wait...\n", __func__);
- rc = wait_event_interruptible(cfg->limbo_waitq,
- cfg->state != STATE_LIMBO);
- if (unlikely(rc))
- break;
- goto retry;
- case STATE_FAILTERM:
- dev_dbg(dev, "%s: Failed/Terminating!\n", __func__);
- rc = -ENODEV;
- break;
- default:
- break;
- }
-
- return rc;
-}
-
-/**
* cxlflash_afu_recover() - initiates AFU recovery
* @sdev: SCSI device associated with LUN.
* @recover: Recover ioctl data structure.
@@ -1647,12 +1654,17 @@ retry_recover:
/* Test if in error state */
reg = readq_be(&afu->ctrl_map->mbox_r);
if (reg == -1) {
- dev_dbg(dev, "%s: MMIO read fail! Wait for recovery...\n",
- __func__);
- mutex_unlock(&ctxi->mutex);
+ dev_dbg(dev, "%s: MMIO fail, wait for recovery.\n", __func__);
+
+ /*
+ * Before checking the state, put back the context obtained with
+ * get_context() as it is no longer needed and sleep for a short
+ * period of time (see prolog notes).
+ */
+ put_context(ctxi);
ctxi = NULL;
ssleep(1);
- rc = check_state(cfg);
+ rc = check_state(cfg, true);
if (unlikely(rc))
goto out;
goto retry;
@@ -1946,7 +1958,7 @@ static int ioctl_common(struct scsi_device *sdev, int cmd)
goto out;
}
- rc = check_state(cfg);
+ rc = check_state(cfg, true);
if (unlikely(rc) && (cfg->state == STATE_FAILTERM)) {
switch (cmd) {
case DK_CXLFLASH_VLUN_RESIZE:
@@ -1968,6 +1980,14 @@ out:
* @cmd: IOCTL command.
* @arg: Userspace ioctl data structure.
*
+ * A read/write semaphore is used to implement a 'drain' of currently
+ * running ioctls. The read semaphore is taken at the beginning of each
+ * ioctl thread and released upon concluding execution. Additionally the
+ * semaphore should be released and then reacquired in any ioctl execution
+ * path which will wait for an event to occur that is outside the scope of
+ * the ioctl (i.e. an adapter reset). To drain the ioctls currently running,
+ * a thread simply needs to acquire the write semaphore.
+ *
* Return: 0 on success, -errno on failure
*/
int cxlflash_ioctl(struct scsi_device *sdev, int cmd, void __user *arg)
@@ -2002,6 +2022,9 @@ int cxlflash_ioctl(struct scsi_device *sdev, int cmd, void __user *arg)
{sizeof(struct dk_cxlflash_clone), (sioctl)cxlflash_disk_clone},
};
+ /* Hold read semaphore so we can drain if needed */
+ down_read(&cfg->ioctl_rwsem);
+
/* Restrict command set to physical support only for internal LUN */
if (afu->internal_lun)
switch (cmd) {
@@ -2083,6 +2106,7 @@ int cxlflash_ioctl(struct scsi_device *sdev, int cmd, void __user *arg)
/* fall through to exit */
cxlflash_ioctl_exit:
+ up_read(&cfg->ioctl_rwsem);
if (unlikely(rc && known_ioctl))
dev_err(dev, "%s: ioctl %s (%08X) on dev(%d/%d/%d/%llu) "
"returned rc %d\n", __func__,
--
2.1.0
--
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