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Subject[PATCH v5 2/9] 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 | 49 +++++++++++++++++++++++++++++++++++++++++++++
include/linux/dax.h | 17 ++++++++++++++++
2 files changed, 66 insertions(+)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 5fa6ae9dbc8b..22f0aa3f2e13 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -222,8 +222,11 @@ struct dax_device {
struct cdev cdev;
const char *host;
void *private;
+ struct rw_semaphore holder_rwsem;
+ void *holder_data;
unsigned long flags;
const struct dax_operations *ops;
+ const struct dax_holder_operations *holder_ops;
};

static ssize_t write_cache_show(struct device *dev,
@@ -373,6 +376,24 @@ 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, void *data)
+{
+ int rc = -ENXIO;
+ if (!dax_dev)
+ return rc;
+
+ if (dax_dev->holder_data) {
+ rc = dax_dev->holder_ops->notify_failure(dax_dev, offset,
+ size, data);
+ if (rc == -ENODEV)
+ rc = -ENXIO;
+ } else
+ rc = -EOPNOTSUPP;
+ 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)
@@ -603,6 +624,7 @@ struct dax_device *alloc_dax(void *private, const char *__host,
dax_add_host(dax_dev, host);
dax_dev->ops = ops;
dax_dev->private = private;
+ init_rwsem(&dax_dev->holder_rwsem);
if (flags & DAXDEV_F_SYNC)
set_dax_synchronous(dax_dev);

@@ -624,6 +646,33 @@ 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)
+{
+ if (!dax_dev)
+ return;
+ down_write(&dax_dev->holder_rwsem);
+ dax_dev->holder_data = holder;
+ dax_dev->holder_ops = ops;
+ up_write(&dax_dev->holder_rwsem);
+}
+EXPORT_SYMBOL_GPL(dax_set_holder);
+
+void *dax_get_holder(struct dax_device *dax_dev)
+{
+ void *holder_data;
+
+ if (!dax_dev)
+ return NULL;
+
+ down_read(&dax_dev->holder_rwsem);
+ holder_data = dax_dev->holder_data;
+ up_read(&dax_dev->holder_rwsem);
+
+ return holder_data;
+}
+EXPORT_SYMBOL_GPL(dax_get_holder);
+
/**
* dax_get_by_host() - temporary lookup mechanism for filesystem-dax
* @host: alternate name for the device registered by a dax driver
diff --git a/include/linux/dax.h b/include/linux/dax.h
index b52f084aa643..6f4b5c97ceb0 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -38,10 +38,17 @@ struct dax_operations {
int (*zero_page_range)(struct dax_device *, pgoff_t, size_t);
};

+struct dax_holder_operations {
+ int (*notify_failure)(struct dax_device *, loff_t, size_t, void *);
+};
+
extern struct attribute_group dax_attribute_group;

#if IS_ENABLED(CONFIG_DAX)
struct dax_device *dax_get_by_host(const char *host);
+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);
@@ -77,6 +84,14 @@ 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)
{
@@ -226,6 +241,8 @@ 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, void *data);
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,
--
2.32.0


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