On 9/8/26 04:56, Zi Yan wrote:
> folio->private != NULL indicates a folio carries private data, replacing
> PG_private. All PG_private users are converted. Remove PG_private and
> reserve the space as __PG_folio for future use.
>
> __DEF_PAGEFLAG_NAME() is added to show __PG_folio.
>
> Also update files in Documentation. hugetlbfs_reserv.rst is outdated and
> left unchanged. It should be rewritten.
>
> Assisted-by: Claude:claude-opus-4-8
> Assisted-by: Codex:gpt-5
> Signed-off-by: Zi Yan <[email protected]>
> To: Andrew Morton <[email protected]>
> To: Baoquan He <[email protected]>
> To: Mike Rapoport <[email protected]>
> To: Pasha Tatashin <[email protected]>
> To: Pratyush Yadav <[email protected]>
> To: Jonathan Corbet <[email protected]>
> To: "Matthew Wilcox (Oracle)" <[email protected]>
> To: Jan Kara <[email protected]>
> To: David Hildenbrand <[email protected]>
> To: Steven Rostedt <[email protected]>
> To: Masami Hiramatsu <[email protected]>
> Cc: Dave Young <[email protected]>
> Cc: Shuah Khan <[email protected]>
> Cc: Lorenzo Stoakes <[email protected]>
> Cc: "Liam R. Howlett" <[email protected]>
> Cc: Vlastimil Babka <[email protected]>
> Cc: Suren Baghdasaryan <[email protected]>
> Cc: Michal Hocko <[email protected]>
> Cc: Mathieu Desnoyers <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> ---
> Documentation/admin-guide/kdump/vmcoreinfo.rst | 2 +-
> Documentation/filesystems/vfs.rst | 6 +++---
> include/linux/page-flags.h | 19 ++-----------------
> include/trace/events/mmflags.h | 3 ++-
> kernel/vmcore_info.c | 1 -
> 5 files changed, 8 insertions(+), 23 deletions(-)
>
> diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst
> b/Documentation/admin-guide/kdump/vmcoreinfo.rst
> index 7663c610fe901..5f1df6d080508 100644
> --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
> +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
> @@ -325,7 +325,7 @@ NR_FREE_PAGES
> On linux-2.6.21 or later, the number of free pages is in
> vm_stat[NR_FREE_PAGES]. Used to get the number of free pages.
>
> -PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_hwpoison|PG_head_mask
> +PG_lru|PG_swapcache|PG_swapbacked|PG_hwpoison|PG_head_mask
> --------------------------------------------------------------------------
>
> Page attributes. These flags are used to filter various unnecessary for
> diff --git a/Documentation/filesystems/vfs.rst
> b/Documentation/filesystems/vfs.rst
> index d3a93eec3945f..dec7816303c6a 100644
> --- a/Documentation/filesystems/vfs.rst
> +++ b/Documentation/filesystems/vfs.rst
> @@ -649,8 +649,8 @@ Writeback.
>
> The first can be used independently to the others. The VM can try to
> release clean pages in order to reuse them. To do this it can call
> -->release_folio on clean folios with the private
> -flag set. Clean pages without PagePrivate and with no external references
> +->release_folio on clean folios with folio->private set. Clean pages
> +without folio->private set and with no external references
> will be released without notice being given to the address_space.
This reads like it would belong into patch #13?
>
> To achieve this functionality, pages need to be placed on an LRU with
> @@ -674,7 +674,7 @@ filemap_fdatawait_range, to wait for all writeback to
> complete.
>
> An address_space handler may attach extra information to a page,
> typically using the 'private' field in the 'struct page'. If such
> -information is attached, the PG_Private flag should be set. This will
> +information is attached, non-NULL 'private' field will
Same here?
Likely this could have been restructured to cause less head scratches. I'd
expect any documentation that refers to PG_private to get removed before finally
removing the bit.
Not the end of the world, just a bit confusing while reviewing.
> cause various VM routines to make extra calls into the address_space
> handler to deal with that data.
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index ce7fccd90367b..7b7783c0a5216 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -44,10 +44,6 @@
> * Consequently, PG_reserved for a page mapped into user space can indicate
> * the zero page, the vDSO, MMIO pages or device memory.
> *
> - * The PG_private bitflag is set on pagecache pages if they contain
> filesystem
> - * specific data (which is normally at page->private). It can be used by
> - * private allocations for its own usage.
> - *
> * During initiation of disk I/O, PG_locked is set. This bit is set before
> I/O
> * and cleared when writeback _starts_ or when read _completes_. PG_writeback
> * is set before writeback starts and cleared when it finishes.
> @@ -105,7 +101,7 @@ enum pageflags {
> PG_owner_2, /* Owner use. If pagecache, fs may use */
> PG_arch_1,
> PG_reserved,
> - PG_private, /* If pagecache, has fs-private data */
> + __PG_folio, /* Do not use: reserved for folio
> identification */
Do we really have to annotate it with __PG_folio ? I'd just keep it simple and
have the comment. That also avoids __DEF_PAGEFLAG_NAME just for this use case.
(sorry if this was discussed in previous review rounds)
--
Cheers,
David
