From: John Groves <[email protected]> The fs_dax_get() function should be called by fs-dax file systems after opening a fsdev dax device. This adds holder_operations, which provides a memory failure callback path and effects exclusivity between callers of fs_dax_get().
fs_dax_get() is specific to fsdev_dax, so it checks the driver type (which required touching bus.[ch]). fs_dax_get() fails if fsdev_dax is not bound to the memory. This function serves the same role as fs_dax_get_by_bdev(), which dax file systems call after opening the pmem block device. This can't be located in fsdev.c because struct dax_device is opaque there. This will be called by fs/fuse/famfs.c in a subsequent commit. Signed-off-by: John Groves <[email protected]> --- drivers/dax/bus.c | 2 -- drivers/dax/bus.h | 2 ++ drivers/dax/super.c | 58 ++++++++++++++++++++++++++++++++++++++++++++- include/linux/dax.h | 20 ++++++++++------ 4 files changed, 72 insertions(+), 10 deletions(-) diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c index e79daf825b52..01402d5103ef 100644 --- a/drivers/dax/bus.c +++ b/drivers/dax/bus.c @@ -39,8 +39,6 @@ static int dax_bus_uevent(const struct device *dev, struct kobj_uevent_env *env) return add_uevent_var(env, "MODALIAS=" DAX_DEVICE_MODALIAS_FMT, 0); } -#define to_dax_drv(__drv) container_of_const(__drv, struct dax_device_driver, drv) - static struct dax_id *__dax_match_id(const struct dax_device_driver *dax_drv, const char *dev_name) { diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h index 880bdf7e72d7..dc6f112ac4a4 100644 --- a/drivers/dax/bus.h +++ b/drivers/dax/bus.h @@ -42,6 +42,8 @@ struct dax_device_driver { void (*remove)(struct dev_dax *dev); }; +#define to_dax_drv(__drv) container_of_const(__drv, struct dax_device_driver, drv) + int __dax_driver_register(struct dax_device_driver *dax_drv, struct module *module, const char *mod_name); #define dax_driver_register(driver) \ diff --git a/drivers/dax/super.c b/drivers/dax/super.c index ba0b4cd18a77..00c330ef437c 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -14,6 +14,7 @@ #include <linux/fs.h> #include <linux/cacheinfo.h> #include "dax-private.h" +#include "bus.h" /** * struct dax_device - anchor object for dax services @@ -111,6 +112,10 @@ struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, u64 *start_off, } EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev); +#endif /* CONFIG_BLOCK && CONFIG_FS_DAX */ + +#if IS_ENABLED(CONFIG_FS_DAX) + void fs_put_dax(struct dax_device *dax_dev, void *holder) { if (dax_dev && holder && @@ -119,7 +124,58 @@ void fs_put_dax(struct dax_device *dax_dev, void *holder) put_dax(dax_dev); } EXPORT_SYMBOL_GPL(fs_put_dax); -#endif /* CONFIG_BLOCK && CONFIG_FS_DAX */ + +/** + * fs_dax_get() - get ownership of a devdax via holder/holder_ops + * + * fs-dax file systems call this function to prepare to use a devdax device for + * fsdax. This is like fs_dax_get_by_bdev(), but the caller already has struct + * dev_dax (and there is no bdev). The holder makes this exclusive. + * + * @dax_dev: dev to be prepared for fs-dax usage + * @holder: filesystem or mapped device inside the dax_device + * @hops: operations for the inner holder + * + * Returns: 0 on success, <0 on failure + */ +int fs_dax_get(struct dax_device *dax_dev, void *holder, + const struct dax_holder_operations *hops) +{ + struct dev_dax *dev_dax; + struct dax_device_driver *dax_drv; + int id; + + id = dax_read_lock(); + if (!dax_dev || !dax_alive(dax_dev) || !igrab(&dax_dev->inode)) { + dax_read_unlock(id); + return -ENODEV; + } + dax_read_unlock(id); + + /* Verify the device is bound to fsdev_dax driver */ + dev_dax = dax_get_private(dax_dev); + if (!dev_dax || !dev_dax->dev.driver) { + iput(&dax_dev->inode); + return -ENODEV; + } + + dax_drv = to_dax_drv(dev_dax->dev.driver); + if (dax_drv->type != DAXDRV_FSDEV_TYPE) { + iput(&dax_dev->inode); + return -EOPNOTSUPP; + } + + if (cmpxchg(&dax_dev->holder_data, NULL, holder)) { + iput(&dax_dev->inode); + return -EBUSY; + } + + dax_dev->holder_ops = hops; + + return 0; +} +EXPORT_SYMBOL_GPL(fs_dax_get); +#endif /* CONFIG_FS_DAX */ enum dax_device_flags { /* !alive + rcu grace period == no new operations / mappings */ diff --git a/include/linux/dax.h b/include/linux/dax.h index 5aaaca135737..6897c5736543 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -52,9 +52,6 @@ struct dax_holder_operations { #if IS_ENABLED(CONFIG_DAX) struct dax_device *alloc_dax(void *private, const struct dax_operations *ops); -#if IS_ENABLED(CONFIG_DEV_DAX_FS) -struct dax_device *inode_dax(struct inode *inode); -#endif void *dax_holder(struct dax_device *dax_dev); void put_dax(struct dax_device *dax_dev); void kill_dax(struct dax_device *dax_dev); @@ -134,7 +131,6 @@ int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk); void dax_remove_host(struct gendisk *disk); struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, u64 *start_off, void *holder, const struct dax_holder_operations *ops); -void fs_put_dax(struct dax_device *dax_dev, void *holder); #else static inline int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk) { @@ -149,12 +145,13 @@ static inline struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev, { return NULL; } -static inline void fs_put_dax(struct dax_device *dax_dev, void *holder) -{ -} #endif /* CONFIG_BLOCK && CONFIG_FS_DAX */ #if IS_ENABLED(CONFIG_FS_DAX) +void fs_put_dax(struct dax_device *dax_dev, void *holder); +int fs_dax_get(struct dax_device *dax_dev, void *holder, + const struct dax_holder_operations *hops); +struct dax_device *inode_dax(struct inode *inode); int dax_writeback_mapping_range(struct address_space *mapping, struct dax_device *dax_dev, struct writeback_control *wbc); int dax_folio_reset_order(struct folio *folio); @@ -168,6 +165,15 @@ dax_entry_t dax_lock_mapping_entry(struct address_space *mapping, void dax_unlock_mapping_entry(struct address_space *mapping, unsigned long index, dax_entry_t cookie); #else +static inline void fs_put_dax(struct dax_device *dax_dev, void *holder) +{ +} + +static inline int fs_dax_get(struct dax_device *dax_dev, void *holder, + const struct dax_holder_operations *hops) +{ + return -EOPNOTSUPP; +} static inline struct page *dax_layout_busy_page(struct address_space *mapping) { return NULL; -- 2.52.0
