From c87dd99b6d0fe07e836c1593c03e8174029c66f4 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Mon, 19 Oct 2026 14:56:11 +0200 Subject: [PATCH] dax: add fsdev_dax_from_file() If the file is a fsdev_dax open, take the dax_dev from the device inode's i_cdev. Return with a reference grabbed on the private dax inode. Make dax_dev_get() static again (internal to super.c for alloc_dax), export fsdev_dax_from_file() instead. This fix is in response to a Sashiko review, and some subsequent analysis. About the 'fixes' tag: this removes the export of dax_dev_get(), which was flawed, and replaces it with fsdev_dax_from_file(). It feels like the fixes tag makes sense for correcting an ABI error. Fixes: 2ae624d5a555d ("dax: export dax_dev_get()") Originally-by: John Groves Reviewed-by: Dave Jiang Reviewed-by: Gregory Price (Meta) Signed-off-by: Miklos Szeredi --- drivers/dax/fsdev.c | 23 +++++++++++++++++++++++ drivers/dax/super.c | 3 +-- include/linux/dax.h | 3 ++- 3 files changed, 26 insertions(+), 3 deletions(-) diff --git a/drivers/dax/fsdev.c b/drivers/dax/fsdev.c index 598604bf5ac5..910665c1f492 100644 --- a/drivers/dax/fsdev.c +++ b/drivers/dax/fsdev.c @@ -234,6 +234,29 @@ static const struct file_operations fsdev_fops = { .release = fsdev_release, }; +/** + * fsdev_dax_from_file - get dax_device from an open file + * @file: open device file + * + * Returns a dax_device pointer if @file refers to a fsdev_dax device. + * Otherwise return NULL. + * + * Caller must put_dax() the returned device when done. + */ +struct dax_device *fsdev_dax_from_file(struct file *file) +{ + struct dax_device *dax_dev; + + if (file->f_op != &fsdev_fops) + return NULL; + + dax_dev = inode_dax(file_inode(file)); + ihold(dax_inode(dax_dev)); + + return dax_dev; +} +EXPORT_SYMBOL_GPL(fsdev_dax_from_file); + /* * Acquire the dev_pagemap for probe: the static (pre-populated) one if * present, or a devm-allocated one for the dynamic case. Note that diff --git a/drivers/dax/super.c b/drivers/dax/super.c index 45f84b0eb909..25836f389bde 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -565,7 +565,7 @@ static int dax_set(struct inode *inode, void *data) return 0; } -struct dax_device *dax_dev_get(dev_t devt) +static struct dax_device *dax_dev_get(dev_t devt) { struct dax_device *dax_dev; struct inode *inode; @@ -588,7 +588,6 @@ struct dax_device *dax_dev_get(dev_t devt) return dax_dev; } -EXPORT_SYMBOL_GPL(dax_dev_get); struct dax_device *alloc_dax(void *private, const struct dax_operations *ops) { diff --git a/include/linux/dax.h b/include/linux/dax.h index fe6c3ded1b50..2c9fc81f031b 100644 --- a/include/linux/dax.h +++ b/include/linux/dax.h @@ -54,7 +54,6 @@ struct dax_device *alloc_dax(void *private, const struct dax_operations *ops); void *dax_holder(struct dax_device *dax_dev); void put_dax(struct dax_device *dax_dev); void kill_dax(struct dax_device *dax_dev); -struct dax_device *dax_dev_get(dev_t devt); void dax_write_cache(struct dax_device *dax_dev, bool wc); bool dax_write_cache_enabled(struct dax_device *dax_dev); bool dax_synchronous(struct dax_device *dax_dev); @@ -323,3 +322,5 @@ typedef int (*walk_hmem_fn)(struct device *dev, int target_nid, const struct resource *res); int walk_hmem_resources(struct device *dev, walk_hmem_fn fn); #endif + +struct dax_device *fsdev_dax_from_file(struct file *file);