s390/pci: Serialize device addition and removal

Prior changes ensured that when zpci_release_device() is called and it
removed the zdev from the zpci_list this instance can not be found via
the zpci_list anymore even while allowing re-add of reserved devices.
This only accounts for the overall lifetime and zpci_list addition and
removal, it does not yet prevent concurrent add of a new instance for
the same underlying device. Such concurrent add would subsequently cause
issues such as attempted re-use of the same IOMMU sysfs directory and is
generally undesired.

Introduce a new zpci_add_remove_lock mutex to serialize adding a new
device with removal. Together this ensures that if a struct zpci_dev is
not found in the zpci_list it was either already removed and torn down,
or its removal and tear down is in progress with the
zpci_add_remove_lock held.

Cc: stable@vger.kernel.org
Fixes: a46044a92add ("s390/pci: fix zpci_zdev_put() on reserve")
Reviewed-by: Gerd Bayer <gbayer@linux.ibm.com>
Tested-by: Gerd Bayer <gbayer@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index 4602abd0c6f1fc8267694c9ec1652c1517b10b05..cd6676c2d6022d60e3358484d5674a9b65880829 100644 (file)
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -45,6 +45,7 @@
 /* list of all detected zpci devices */
 static LIST_HEAD(zpci_list);
 static DEFINE_SPINLOCK(zpci_list_lock);
+static DEFINE_MUTEX(zpci_add_remove_lock);
 
 static DECLARE_BITMAP(zpci_domain, ZPCI_DOMAIN_BITMAP_SIZE);
 static DEFINE_SPINLOCK(zpci_domain_lock);
@@ -74,7 +75,9 @@ void zpci_zdev_put(struct zpci_dev *zdev)
 {
        if (!zdev)
                return;
+       mutex_lock(&zpci_add_remove_lock);
        kref_put_lock(&zdev->kref, zpci_release_device, &zpci_list_lock);
+       mutex_unlock(&zpci_add_remove_lock);
 }
 
 struct zpci_dev *get_zdev_by_fid(u32 fid)
@@ -844,6 +847,7 @@ int zpci_add_device(struct zpci_dev *zdev)
 {
        int rc;
 
+       mutex_lock(&zpci_add_remove_lock);
        zpci_dbg(1, "add fid:%x, fh:%x, c:%d\n", zdev->fid, zdev->fh, zdev->state);
        rc = zpci_init_iommu(zdev);
        if (rc)
@@ -857,12 +861,14 @@ int zpci_add_device(struct zpci_dev *zdev)
        spin_lock(&zpci_list_lock);
        list_add_tail(&zdev->entry, &zpci_list);
        spin_unlock(&zpci_list_lock);
+       mutex_unlock(&zpci_add_remove_lock);
        return 0;
 
 error_destroy_iommu:
        zpci_destroy_iommu(zdev);
 error:
        zpci_dbg(0, "add fid:%x, rc:%d\n", zdev->fid, rc);
+       mutex_unlock(&zpci_add_remove_lock);
        return rc;
 }
 
@@ -953,6 +959,7 @@ void zpci_release_device(struct kref *kref)
 {
        struct zpci_dev *zdev = container_of(kref, struct zpci_dev, kref);
 
+       lockdep_assert_held(&zpci_add_remove_lock);
        WARN_ON(zdev->state != ZPCI_FN_STATE_RESERVED);
        /*
         * We already hold zpci_list_lock thanks to kref_put_lock().