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Subject[PATCH v7 2/8] dax: Introduce holder for dax_device
Date
To easily track filesystem from a pmem device, we introduce a holder for
dax_device structure, and also its operation. This holder is used to
remember who is using this dax_device:
- When it is the backend of a filesystem, the holder will be the
superblock of this filesystem.
- When this pmem device is one of the targets in a mapped device, the
holder will be this mapped device. In this case, the mapped device
has its own dax_device and it will follow the first rule. So that we
can finally track to the filesystem we needed.

The holder and holder_ops will be set when filesystem is being mounted,
or an target device is being activated.

Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
---
drivers/dax/super.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/dax.h | 29 ++++++++++++++++++++++
2 files changed, 88 insertions(+)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 48ce86501d93..7d4a11dcba90 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -23,7 +23,10 @@
* @cdev: optional character interface for "device dax"
* @host: optional name for lookups where the device path is not available
* @private: dax driver private data
+ * @holder_data: holder of a dax_device: could be filesystem or mapped device
* @flags: state and boolean properties
+ * @ops: operations for dax_device
+ * @holder_ops: operations for the inner holder
*/
struct dax_device {
struct hlist_node list;
@@ -31,8 +34,10 @@ struct dax_device {
struct cdev cdev;
const char *host;
void *private;
+ void *holder_data;
unsigned long flags;
const struct dax_operations *ops;
+ const struct dax_holder_operations *holder_ops;
};

static dev_t dax_devt;
@@ -374,6 +379,29 @@ int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
}
EXPORT_SYMBOL_GPL(dax_zero_page_range);

+int dax_holder_notify_failure(struct dax_device *dax_dev, loff_t offset,
+ size_t size, int flags)
+{
+ int rc;
+
+ dax_read_lock();
+ if (!dax_alive(dax_dev)) {
+ rc = -ENXIO;
+ goto out;
+ }
+
+ if (!dax_dev->holder_data) {
+ rc = -EOPNOTSUPP;
+ goto out;
+ }
+
+ rc = dax_dev->holder_ops->notify_failure(dax_dev, offset, size, flags);
+out:
+ dax_read_unlock();
+ return rc;
+}
+EXPORT_SYMBOL_GPL(dax_holder_notify_failure);
+
#ifdef CONFIG_ARCH_HAS_PMEM_API
void arch_wb_cache_pmem(void *addr, size_t size);
void dax_flush(struct dax_device *dax_dev, void *addr, size_t size)
@@ -618,6 +646,37 @@ void put_dax(struct dax_device *dax_dev)
}
EXPORT_SYMBOL_GPL(put_dax);

+void dax_set_holder(struct dax_device *dax_dev, void *holder,
+ const struct dax_holder_operations *ops)
+{
+ dax_write_lock();
+ if (!dax_alive(dax_dev)) {
+ dax_write_unlock();
+ return;
+ }
+
+ dax_dev->holder_data = holder;
+ dax_dev->holder_ops = ops;
+ dax_write_unlock();
+}
+EXPORT_SYMBOL_GPL(dax_set_holder);
+
+void *dax_get_holder(struct dax_device *dax_dev)
+{
+ void *holder;
+
+ dax_read_lock();
+ if (!dax_alive(dax_dev)) {
+ dax_read_unlock();
+ return NULL;
+ }
+
+ holder = dax_dev->holder_data;
+ dax_read_unlock();
+ return holder;
+}
+EXPORT_SYMBOL_GPL(dax_get_holder);
+
/**
* inode_dax: convert a public inode into its dax_dev
* @inode: An inode with i_cdev pointing to a dax_dev
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 097b3304f9b9..d273d59723cd 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -38,9 +38,24 @@ struct dax_operations {
int (*zero_page_range)(struct dax_device *, pgoff_t, size_t);
};

+struct dax_holder_operations {
+ /*
+ * notify_failure - notify memory failure into inner holder device
+ * @dax_dev: the dax device which contains the holder
+ * @offset: offset on this dax device where memory failure occurs
+ * @size: length of this memory failure event
+ * @flags: action flags for memory failure handler
+ */
+ int (*notify_failure)(struct dax_device *dax_dev, loff_t offset,
+ size_t size, int flags);
+};
+
extern struct attribute_group dax_attribute_group;

#if IS_ENABLED(CONFIG_DAX)
+void dax_set_holder(struct dax_device *dax_dev, void *holder,
+ const struct dax_holder_operations *ops);
+void *dax_get_holder(struct dax_device *dax_dev);
struct dax_device *alloc_dax(void *private, const char *host,
const struct dax_operations *ops, unsigned long flags);
void put_dax(struct dax_device *dax_dev);
@@ -70,6 +85,18 @@ static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
return dax_synchronous(dax_dev);
}
#else
+static inline struct dax_device *dax_get_by_host(const char *host)
+{
+ return NULL;
+}
+static inline void dax_set_holder(struct dax_device *dax_dev, void *holder,
+ const struct dax_holder_operations *ops)
+{
+}
+static inline void *dax_get_holder(struct dax_device *dax_dev)
+{
+ return NULL;
+}
static inline struct dax_device *alloc_dax(void *private, const char *host,
const struct dax_operations *ops, unsigned long flags)
{
@@ -198,6 +225,8 @@ size_t dax_copy_to_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
size_t bytes, struct iov_iter *i);
int dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
size_t nr_pages);
+int dax_holder_notify_failure(struct dax_device *dax_dev, loff_t offset,
+ size_t size, int flags);
void dax_flush(struct dax_device *dax_dev, void *addr, size_t size);

ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
--
2.33.0


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