Re: [PATCH v2 4/7] filemap: Add fgp_t typedef

Darrick J. Wong
2023-06-04T18:02:47Z

On Fri, Jun 02, 2023 at 11:24:41PM +0100, Matthew Wilcox (Oracle) wrote:
> Similarly to gfp_t, define fgp_t as its own type to prevent various
> misuses and confusion. Move the documentation to the definition of the
> type insted of burying it in the __filemap_get_folio() documentation.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

This looks like a pretty straightforward change
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
> fs/btrfs/file.c | 6 +++---
> fs/f2fs/compress.c | 2 +-
> fs/f2fs/f2fs.h | 2 +-
> fs/iomap/buffered-io.c | 2 +-
> include/linux/pagemap.h | 48 +++++++++++++++++++++++++++++++----------
> mm/filemap.c | 19 ++--------------
> mm/folio-compat.c | 2 +-
> 7 files changed, 46 insertions(+), 35 deletions(-)
>
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index f649647392e0..4bbbbdafb472 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -876,9 +876,9 @@ static int prepare_uptodate_page(struct inode *inode,
> return 0;
> }
>
> -static unsigned int get_prepare_fgp_flags(bool nowait)
> +static fgp_t get_prepare_fgp_flags(bool nowait)
> {
> - unsigned int fgp_flags = FGP_LOCK | FGP_ACCESSED | FGP_CREAT;
> + fgp_t fgp_flags = FGP_LOCK | FGP_ACCESSED | FGP_CREAT;
>
> if (nowait)
> fgp_flags |= FGP_NOWAIT;
> @@ -910,7 +910,7 @@ static noinline int prepare_pages(struct inode *inode, struct page **pages,
> int i;
> unsigned long index = pos >> PAGE_SHIFT;
> gfp_t mask = get_prepare_gfp_flags(inode, nowait);
> - unsigned int fgp_flags = get_prepare_fgp_flags(nowait);
> + fgp_t fgp_flags = get_prepare_fgp_flags(nowait);
> int err = 0;
> int faili;
>
> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> index 11653fa79289..ee358f5f2a86 100644
> --- a/fs/f2fs/compress.c
> +++ b/fs/f2fs/compress.c
> @@ -1019,7 +1019,7 @@ static int prepare_compress_overwrite(struct compress_ctx *cc,
> struct address_space *mapping = cc->inode->i_mapping;
> struct page *page;
> sector_t last_block_in_bio;
> - unsigned fgp_flag = FGP_LOCK | FGP_WRITE | FGP_CREAT;
> + fgp_t fgp_flag = FGP_LOCK | FGP_WRITE | FGP_CREAT;
> pgoff_t start_idx = start_idx_of_cluster(cc);
> int i, ret;
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index d211ee89c158..a03c3df75f7c 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2715,7 +2715,7 @@ static inline struct page *f2fs_grab_cache_page(struct address_space *mapping,
>
> static inline struct page *f2fs_pagecache_get_page(
> struct address_space *mapping, pgoff_t index,
> - int fgp_flags, gfp_t gfp_mask)
> + fgp_t fgp_flags, gfp_t gfp_mask)
> {
> if (time_to_inject(F2FS_M_SB(mapping), FAULT_PAGE_GET))
> return NULL;
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 2054b85c9d9b..30d53b50ee0f 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -467,7 +467,7 @@ EXPORT_SYMBOL_GPL(iomap_is_partially_uptodate);
> */
> struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos)
> {
> - unsigned fgp = FGP_WRITEBEGIN | FGP_NOFS;
> + fgp_t fgp = FGP_WRITEBEGIN | FGP_NOFS;
>
> if (iter->flags & IOMAP_NOWAIT)
> fgp |= FGP_NOWAIT;
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index a56308a9d1a4..7ab57a2bb576 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -497,22 +497,48 @@ pgoff_t page_cache_next_miss(struct address_space *mapping,
> pgoff_t page_cache_prev_miss(struct address_space *mapping,
> pgoff_t index, unsigned long max_scan);
>
> -#define FGP_ACCESSED 0x00000001
> -#define FGP_LOCK 0x00000002
> -#define FGP_CREAT 0x00000004
> -#define FGP_WRITE 0x00000008
> -#define FGP_NOFS 0x00000010
> -#define FGP_NOWAIT 0x00000020
> -#define FGP_FOR_MMAP 0x00000040
> -#define FGP_STABLE 0x00000080
> +/**
> + * typedef fgp_t - Flags for getting folios from the page cache.
> + *
> + * Most users of the page cache will not need to use these flags;
> + * there are convenience functions such as filemap_get_folio() and
> + * filemap_lock_folio(). For users which need more control over exactly
> + * what is done with the folios, these flags to __filemap_get_folio()
> + * are available.
> + *
> + * * %FGP_ACCESSED - The folio will be marked accessed.
> + * * %FGP_LOCK - The folio is returned locked.
> + * * %FGP_CREAT - If no folio is present then a new folio is allocated,
> + * added to the page cache and the VM's LRU list. The folio is
> + * returned locked.
> + * * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the
> + * folio is already in cache. If the folio was allocated, unlock it
> + * before returning so the caller can do the same dance.
> + * * %FGP_WRITE - The folio will be written to by the caller.
> + * * %FGP_NOFS - __GFP_FS will get cleared in gfp.
> + * * %FGP_NOWAIT - Don't block on the folio lock.
> + * * %FGP_STABLE - Wait for the folio to be stable (finished writeback)
> + * * %FGP_WRITEBEGIN - The flags to use in a filesystem write_begin()
> + * implementation.
> + */
> +typedef unsigned int __bitwise fgp_t;
> +
> +#define FGP_ACCESSED ((__force fgp_t)0x00000001)
> +#define FGP_LOCK ((__force fgp_t)0x00000002)
> +#define FGP_CREAT ((__force fgp_t)0x00000004)
> +#define FGP_WRITE ((__force fgp_t)0x00000008)
> +#define FGP_NOFS ((__force fgp_t)0x00000010)
> +#define FGP_NOWAIT ((__force fgp_t)0x00000020)
> +#define FGP_FOR_MMAP ((__force fgp_t)0x00000040)
> +#define FGP_STABLE ((__force fgp_t)0x00000080)
>
> #define FGP_WRITEBEGIN (FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE)
>
> void *filemap_get_entry(struct address_space *mapping, pgoff_t index);
> struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
> - int fgp_flags, gfp_t gfp);
> + fgp_t fgp_flags, gfp_t gfp);
> struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
> - int fgp_flags, gfp_t gfp);
> + fgp_t fgp_flags, gfp_t gfp);
>
> /**
> * filemap_get_folio - Find and get a folio.
> @@ -586,7 +612,7 @@ static inline struct page *find_get_page(struct address_space *mapping,
> }
>
> static inline struct page *find_get_page_flags(struct address_space *mapping,
> - pgoff_t offset, int fgp_flags)
> + pgoff_t offset, fgp_t fgp_flags)
> {
> return pagecache_get_page(mapping, offset, fgp_flags, 0);
> }
> diff --git a/mm/filemap.c b/mm/filemap.c
> index b4c9bd368b7e..eb89a815f2f8 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1887,30 +1887,15 @@ void *filemap_get_entry(struct address_space *mapping, pgoff_t index)
> *
> * Looks up the page cache entry at @mapping & @index.
> *
> - * @fgp_flags can be zero or more of these flags:
> - *
> - * * %FGP_ACCESSED - The folio will be marked accessed.
> - * * %FGP_LOCK - The folio is returned locked.
> - * * %FGP_CREAT - If no page is present then a new page is allocated using
> - * @gfp and added to the page cache and the VM's LRU list.
> - * The page is returned locked and with an increased refcount.
> - * * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the
> - * page is already in cache. If the page was allocated, unlock it before
> - * returning so the caller can do the same dance.
> - * * %FGP_WRITE - The page will be written to by the caller.
> - * * %FGP_NOFS - __GFP_FS will get cleared in gfp.
> - * * %FGP_NOWAIT - Don't get blocked by page lock.
> - * * %FGP_STABLE - Wait for the folio to be stable (finished writeback)
> - *
> * If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
> * if the %GFP flags specified for %FGP_CREAT are atomic.
> *
> - * If there is a page cache page, it is returned with an increased refcount.
> + * If this function returns a folio, it is returned with an increased refcount.
> *
> * Return: The found folio or an ERR_PTR() otherwise.
> */
> struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
> - int fgp_flags, gfp_t gfp)
> + fgp_t fgp_flags, gfp_t gfp)
> {
> struct folio *folio;
>
> diff --git a/mm/folio-compat.c b/mm/folio-compat.c
> index c6f056c20503..ae1a737d2533 100644
> --- a/mm/folio-compat.c
> +++ b/mm/folio-compat.c
> @@ -92,7 +92,7 @@ EXPORT_SYMBOL(add_to_page_cache_lru);
>
> noinline
> struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
> - int fgp_flags, gfp_t gfp)
> + fgp_t fgp_flags, gfp_t gfp)
> {
> struct folio *folio;
>
> --
> 2.39.2
>