[PATCH 04/13] fs/dax: Add dax_page_free callback

Alistair Popple
2024-06-27T00:54:58Z

When a fs dax page is freed it has to notify filesystems that the page
has been unpinned/unmapped and is free. Currently this involves
special code in the page free paths to detect a transition of refcount
from 2 to 1 and to call some fs dax specific code.

A future change will require this to happen when the page refcount
drops to zero. In this case we can use the existing
pgmap->ops->page_free() callback so wire that up for all devices that
support FS DAX (nvdimm and virtio).

Signed-off-by: Alistair Popple <apopple@nvidia.com>
---
drivers/nvdimm/pmem.c | 1 +
fs/dax.c | 6 ++++++
fs/fuse/virtio_fs.c | 5 +++++
include/linux/dax.h | 1 +
4 files changed, 13 insertions(+)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 598fe2e..cafadd0 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -444,6 +444,7 @@ static int pmem_pagemap_memory_failure(struct dev_pagemap *pgmap,

static const struct dev_pagemap_ops fsdax_pagemap_ops = {
.memory_failure = pmem_pagemap_memory_failure,
+ .page_free = dax_page_free,
};

static int pmem_attach_disk(struct device *dev,
diff --git a/fs/dax.c b/fs/dax.c
index becb4a6..f93afd7 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -2065,3 +2065,9 @@ int dax_remap_file_range_prep(struct file *file_in, loff_t pos_in,
pos_out, len, remap_flags, ops);
}
EXPORT_SYMBOL_GPL(dax_remap_file_range_prep);
+
+void dax_page_free(struct page *page)
+{
+ wake_up_var(page);
+}
+EXPORT_SYMBOL_GPL(dax_page_free);
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 1a52a51..6e90a4b 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -909,6 +909,10 @@ static void virtio_fs_cleanup_dax(void *data)

DEFINE_FREE(cleanup_dax, struct dax_dev *, if (!IS_ERR_OR_NULL(_T)) virtio_fs_cleanup_dax(_T))

+static const struct dev_pagemap_ops fsdax_pagemap_ops = {
+ .page_free = dax_page_free,
+};
+
static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
{
struct dax_device *dax_dev __free(cleanup_dax) = NULL;
@@ -948,6 +952,7 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
return -ENOMEM;

pgmap->type = MEMORY_DEVICE_FS_DAX;
+ pgmap->ops = &fsdax_pagemap_ops;

/* Ideally we would directly use the PCI BAR resource but
* devm_memremap_pages() wants its own copy in pgmap. So
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 773dfc4..adbafc8 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -213,6 +213,7 @@ int dax_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
int dax_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
const struct iomap_ops *ops);

+void dax_page_free(struct page *page);
static inline int dax_wait_page_idle(struct page *page,
void (cb)(struct inode *),
struct inode *inode)
--
git-series 0.9.1