In preparation for adding dax_operations that perform ->direct_access()
and user copy operations relative to a dax_inode, convert the existing
dax_inode locking to srcu. Some dax drivers need to sleep in their
->direct_access() methods and user copying may fault / sleep.
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/dax/Kconfig | 1 +
drivers/dax/device.c | 18 +++++++++---------
drivers/dax/super.c | 20 ++++++++++++++++----
include/linux/dax.h | 3 +++
4 files changed, 29 insertions(+), 13 deletions(-)
diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index 39bcbf4c5e40..b7053eafd88e 100644
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -1,5 +1,6 @@
menuconfig DAX
tristate "DAX: direct access to differentiated memory"
+ select SRCU
default m if NVDIMM_DAX
if DAX
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 5b5572314929..af06d0bfd6ea 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -333,16 +333,16 @@ static int __dax_dev_fault(struct dax_dev *dax_dev, struct vm_area_struct *vma,
static int dax_dev_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
- int rc;
+ int rc, id;
struct file *filp = vma->vm_file;
struct dax_dev *dax_dev = filp->private_data;
dev_dbg(&dax_dev->dev, "%s: %s: %s (%#lx - %#lx)\n", __func__,
current->comm, (vmf->flags & FAULT_FLAG_WRITE)
? "write" : "read", vma->vm_start, vma->vm_end);
- rcu_read_lock();
+ id = dax_read_lock();
rc = __dax_dev_fault(dax_dev, vma, vmf);
- rcu_read_unlock();
+ dax_read_unlock(id);
return rc;
}
@@ -390,7 +390,7 @@ static int __dax_dev_pmd_fault(struct dax_dev *dax_dev,
static int dax_dev_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
pmd_t *pmd, unsigned int flags)
{
- int rc;
+ int rc, id;
struct file *filp = vma->vm_file;
struct dax_dev *dax_dev = filp->private_data;
@@ -398,9 +398,9 @@ static int dax_dev_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
current->comm, (flags & FAULT_FLAG_WRITE)
? "write" : "read", vma->vm_start, vma->vm_end);
- rcu_read_lock();
+ id = dax_read_lock();
rc = __dax_dev_pmd_fault(dax_dev, vma, addr, pmd, flags);
- rcu_read_unlock();
+ dax_read_unlock(id);
return rc;
}
@@ -412,8 +412,8 @@ static const struct vm_operations_struct dax_dev_vm_ops = {
static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
{
+ int rc, id;
struct dax_dev *dax_dev = filp->private_data;
- int rc;
dev_dbg(&dax_dev->dev, "%s\n", __func__);
@@ -421,9 +421,9 @@ static int dax_mmap(struct file *filp, struct vm_area_struct *vma)
* We lock to check dax_inode liveness and will re-check at
* fault time.
*/
- rcu_read_lock();
+ id = dax_read_lock();
rc = check_vma(dax_dev, vma, __func__);
- rcu_read_unlock();
+ dax_read_unlock(id);
if (rc)
return rc;
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index e6369b851619..7c4dc97d53a8 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -24,11 +24,24 @@ module_param(nr_dax, int, S_IRUGO);
MODULE_PARM_DESC(nr_dax, "max number of dax device instances");
static dev_t dax_devt;
+DEFINE_STATIC_SRCU(dax_srcu);
static struct vfsmount *dax_mnt;
static DEFINE_IDA(dax_minor_ida);
static struct kmem_cache *dax_cache __read_mostly;
static struct super_block *dax_superblock __read_mostly;
+int dax_read_lock(void)
+{
+ return srcu_read_lock(&dax_srcu);
+}
+EXPORT_SYMBOL_GPL(dax_read_lock);
+
+void dax_read_unlock(int id)
+{
+ srcu_read_unlock(&dax_srcu, id);
+}
+EXPORT_SYMBOL_GPL(dax_read_unlock);
+
/**
* struct dax_inode - anchor object for dax services
* @inode: core vfs
@@ -45,8 +58,7 @@ struct dax_inode {
bool dax_inode_alive(struct dax_inode *dax_inode)
{
- RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
- "dax operations require rcu_read_lock()\n");
+ lockdep_assert_held(&dax_srcu);
return dax_inode->alive;
}
EXPORT_SYMBOL_GPL(dax_inode_alive);
@@ -55,7 +67,7 @@ EXPORT_SYMBOL_GPL(dax_inode_alive);
* Note, rcu is not protecting the liveness of dax_inode, rcu is
* ensuring that any fault handlers or operations that might have seen
* dax_inode_alive(), have completed. Any operations that start after
- * synchronize_rcu() has run will abort upon seeing !dax_inode_alive().
+ * synchronize_srcu() has run will abort upon seeing !dax_inode_alive().
*/
void kill_dax_inode(struct dax_inode *dax_inode)
{
@@ -63,7 +75,7 @@ void kill_dax_inode(struct dax_inode *dax_inode)
return;
dax_inode->alive = false;
- synchronize_rcu();
+ synchronize_srcu(&dax_srcu);
dax_inode->private = NULL;
}
EXPORT_SYMBOL_GPL(kill_dax_inode);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 24ad71173995..67002898d130 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -8,6 +8,9 @@
struct iomap_ops;
+int dax_read_lock(void);
+void dax_read_unlock(int id);
+
/*
* We use lowest available bit in exceptional entry for locking, one bit for
* the entry size (PMD) and two more to tell us if the entry is a huge zero
--
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