125 lines
3.7 KiB
Diff
125 lines
3.7 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Boris Protopopov <bprotopopov@users.noreply.github.com>
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Date: Wed, 9 Aug 2017 14:10:47 -0400
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Subject: [PATCH] zv_suspend_lock in zvol_open()/zvol_release()
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Acquire zv_suspend_lock on first open and last close only.
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Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
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Signed-off-by: Boris Protopopov <boris.protopopov@actifio.com>
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Closes #6342
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Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
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---
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module/zfs/zvol.c | 64 +++++++++++++++++++++++++++++++++++--------------------
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1 file changed, 41 insertions(+), 23 deletions(-)
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diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c
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index 3e7059b3..ffa5fac7 100644
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--- a/module/zfs/zvol.c
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+++ b/module/zfs/zvol.c
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@@ -1347,9 +1347,9 @@ zvol_open(struct block_device *bdev, fmode_t flag)
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{
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zvol_state_t *zv;
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int error = 0;
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- boolean_t drop_suspend = B_FALSE;
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+ boolean_t drop_suspend = B_TRUE;
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- ASSERT(!mutex_owned(&zvol_state_lock));
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+ ASSERT(!MUTEX_HELD(&zvol_state_lock));
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mutex_enter(&zvol_state_lock);
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/*
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@@ -1364,23 +1364,31 @@ zvol_open(struct block_device *bdev, fmode_t flag)
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return (SET_ERROR(-ENXIO));
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}
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- /* take zv_suspend_lock before zv_state_lock */
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- rw_enter(&zv->zv_suspend_lock, RW_READER);
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-
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mutex_enter(&zv->zv_state_lock);
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-
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/*
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* make sure zvol is not suspended during first open
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- * (hold zv_suspend_lock), otherwise, drop the lock
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+ * (hold zv_suspend_lock) and respect proper lock acquisition
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+ * ordering - zv_suspend_lock before zv_state_lock
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*/
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if (zv->zv_open_count == 0) {
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- drop_suspend = B_TRUE;
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+ if (!rw_tryenter(&zv->zv_suspend_lock, RW_READER)) {
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+ mutex_exit(&zv->zv_state_lock);
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+ rw_enter(&zv->zv_suspend_lock, RW_READER);
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+ mutex_enter(&zv->zv_state_lock);
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+ /* check to see if zv_suspend_lock is needed */
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+ if (zv->zv_open_count != 0) {
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+ rw_exit(&zv->zv_suspend_lock);
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+ drop_suspend = B_FALSE;
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+ }
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+ }
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} else {
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- rw_exit(&zv->zv_suspend_lock);
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+ drop_suspend = B_FALSE;
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}
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-
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mutex_exit(&zvol_state_lock);
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+ ASSERT(MUTEX_HELD(&zv->zv_state_lock));
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+ ASSERT(zv->zv_open_count != 0 || RW_READ_HELD(&zv->zv_suspend_lock));
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+
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if (zv->zv_open_count == 0) {
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error = zvol_first_open(zv);
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if (error)
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@@ -1417,28 +1425,38 @@ static int
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zvol_release(struct gendisk *disk, fmode_t mode)
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{
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zvol_state_t *zv;
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- boolean_t drop_suspend = B_FALSE;
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+ boolean_t drop_suspend = B_TRUE;
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- ASSERT(!mutex_owned(&zvol_state_lock));
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+ ASSERT(!MUTEX_HELD(&zvol_state_lock));
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mutex_enter(&zvol_state_lock);
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zv = disk->private_data;
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- ASSERT(zv && zv->zv_open_count > 0);
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-
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- /* take zv_suspend_lock before zv_state_lock */
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- rw_enter(&zv->zv_suspend_lock, RW_READER);
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mutex_enter(&zv->zv_state_lock);
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- mutex_exit(&zvol_state_lock);
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-
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+ ASSERT(zv->zv_open_count > 0);
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/*
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* make sure zvol is not suspended during last close
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- * (hold zv_suspend_lock), otherwise, drop the lock
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+ * (hold zv_suspend_lock) and respect proper lock acquisition
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+ * ordering - zv_suspend_lock before zv_state_lock
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*/
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- if (zv->zv_open_count == 1)
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- drop_suspend = B_TRUE;
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- else
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- rw_exit(&zv->zv_suspend_lock);
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+ if (zv->zv_open_count == 1) {
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+ if (!rw_tryenter(&zv->zv_suspend_lock, RW_READER)) {
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+ mutex_exit(&zv->zv_state_lock);
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+ rw_enter(&zv->zv_suspend_lock, RW_READER);
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+ mutex_enter(&zv->zv_state_lock);
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+ /* check to see if zv_suspend_lock is needed */
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+ if (zv->zv_open_count != 1) {
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+ rw_exit(&zv->zv_suspend_lock);
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+ drop_suspend = B_FALSE;
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+ }
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+ }
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+ } else {
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+ drop_suspend = B_FALSE;
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+ }
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+ mutex_exit(&zvol_state_lock);
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+
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+ ASSERT(MUTEX_HELD(&zv->zv_state_lock));
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+ ASSERT(zv->zv_open_count != 1 || RW_READ_HELD(&zv->zv_suspend_lock));
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zv->zv_open_count--;
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if (zv->zv_open_count == 0)
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