On Wed 07-10-20 14:49:25, Ralph Campbell wrote:
> There are several places where ZONE_DEVICE struct pages assume a reference
> count == 1 means the page is idle and free. Instead of open coding this,
> add helper functions to hide this detail.
>
> Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Acked-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> Acked-by: Theodore Ts'o <tytso@xxxxxxx> # for fs/ext4/inode.c
The patch looks good to me. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
>
> Changes in v2:
> I strongly resisted the idea of extending this patch but after Jan
> Kara's comment about there being more places that could be cleaned
> up, I felt compelled to make this one tensy wensy change to add
> a dax_wakeup_page() to match the dax_wait_page().
> I kept the Reviewed/Acked-bys since I don't think this substantially
> changes the patch.
>
> fs/dax.c | 4 ++--
> fs/ext4/inode.c | 5 +----
> fs/xfs/xfs_file.c | 4 +---
> include/linux/dax.h | 15 +++++++++++++++
> mm/memremap.c | 3 ++-
> 5 files changed, 21 insertions(+), 10 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 5b47834f2e1b..85c63f735909 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -358,7 +358,7 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping,
> for_each_mapped_pfn(entry, pfn) {
> struct page *page = pfn_to_page(pfn);
>
> - WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
> + WARN_ON_ONCE(trunc && !dax_layout_is_idle_page(page));
> WARN_ON_ONCE(page->mapping && page->mapping != mapping);
> page->mapping = NULL;
> page->index = 0;
> @@ -372,7 +372,7 @@ static struct page *dax_busy_page(void *entry)
> for_each_mapped_pfn(entry, pfn) {
> struct page *page = pfn_to_page(pfn);
>
> - if (page_ref_count(page) > 1)
> + if (!dax_layout_is_idle_page(page))
> return page;
> }
> return NULL;
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 771ed8b1fadb..132620cbfa13 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3937,10 +3937,7 @@ int ext4_break_layouts(struct inode *inode)
> if (!page)
> return 0;
>
> - error = ___wait_var_event(&page->_refcount,
> - atomic_read(&page->_refcount) == 1,
> - TASK_INTERRUPTIBLE, 0, 0,
> - ext4_wait_dax_page(ei));
> + error = dax_wait_page(ei, page, ext4_wait_dax_page);
> } while (error == 0);
>
> return error;
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 3d1b95124744..a5304aaeaa3a 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -749,9 +749,7 @@ xfs_break_dax_layouts(
> return 0;
>
> *retry = true;
> - return ___wait_var_event(&page->_refcount,
> - atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
> - 0, 0, xfs_wait_dax_page(inode));
> + return dax_wait_page(inode, page, xfs_wait_dax_page);
> }
>
> int
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index b52f084aa643..e2da78e87338 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -243,6 +243,21 @@ static inline bool dax_mapping(struct address_space *mapping)
> return mapping->host && IS_DAX(mapping->host);
> }
>
> +static inline bool dax_layout_is_idle_page(struct page *page)
> +{
> + return page_ref_count(page) == 1;
> +}
> +
> +static inline void dax_wakeup_page(struct page *page)
> +{
> + wake_up_var(&page->_refcount);
> +}
> +
> +#define dax_wait_page(_inode, _page, _wait_cb) \
> + ___wait_var_event(&(_page)->_refcount, \
> + dax_layout_is_idle_page(_page), \
> + TASK_INTERRUPTIBLE, 0, 0, _wait_cb(_inode))
> +
> #ifdef CONFIG_DEV_DAX_HMEM_DEVICES
> void hmem_register_device(int target_nid, struct resource *r);
> #else
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 2bb276680837..504a10ff2edf 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -12,6 +12,7 @@
> #include <linux/types.h>
> #include <linux/wait_bit.h>
> #include <linux/xarray.h>
> +#include <linux/dax.h>
>
> static DEFINE_XARRAY(pgmap_array);
>
> @@ -508,7 +509,7 @@ void free_devmap_managed_page(struct page *page)
> {
> /* notify page idle for dax */
> if (!is_device_private_page(page)) {
> - wake_up_var(&page->_refcount);
> + dax_wakeup_page(page);
> return;
> }
>
> --
> 2.20.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
