| Message ID | e626eda568267e1f86d5c30c24bc62474b45f6c3.1719386613.git-series.apopple@nvidia.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | fs/dax: Fix FS DAX page reference counts | expand |
On Thu, Jun 27, 2024 at 10:54:19AM +1000, Alistair Popple wrote: > 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). Given that ->page_ffree is only called from free_zone_device_folio and right next to a switch on the the type, can't we just do the wake_up_var there without the somewhat confusing indirect call that just back in common code without any driver logic?
Christoph Hellwig <hch@lst.de> writes: > On Thu, Jun 27, 2024 at 10:54:19AM +1000, Alistair Popple wrote: >> 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). > > Given that ->page_ffree is only called from free_zone_device_folio > and right next to a switch on the the type, can't we just do the > wake_up_var there without the somewhat confusing indirect call that > just back in common code without any driver logic? Longer term I'm hoping we can get rid of that switch on type entirely as I don't think the whole get/put_dev_pagemap() thing is very useful. Less indirection is good though so will move the wake_up_var there.
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)
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(+)