Re: [PATCH v4 6/9] filemap: Add fgf_t typedef

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Jul 10, 2023 at 02:02:50PM +0100, Matthew Wilcox (Oracle) wrote:
> Similarly to gfp_t, define fgf_t as its own type to prevent various
> misuses and confusion.  Leave the flags as FGP_* for now to reduce the
> size of this patch; they will be converted to FGF_* later.  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>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Yay!
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 fd03e689a6be..3876fae90fc3 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 fgf_t get_prepare_fgp_flags(bool nowait)
>  {
> -	unsigned int fgp_flags = FGP_LOCK | FGP_ACCESSED | FGP_CREAT;
> +	fgf_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);
> +	fgf_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 236d890f560b..0f7df9c11af3 100644
> --- a/fs/f2fs/compress.c
> +++ b/fs/f2fs/compress.c
> @@ -1045,7 +1045,7 @@ 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;
> +	fgf_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 c7cb2177b252..c275ff2753c2 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -2736,7 +2736,7 @@ 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)
> +				fgf_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 7aa3009f907f..5e9380cc3e83 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;
> +	fgf_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 716953ee1ebd..911201fc41fc 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -501,22 +501,48 @@ 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 fgf_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 fgf_t;
> +
> +#define FGP_ACCESSED		((__force fgf_t)0x00000001)
> +#define FGP_LOCK		((__force fgf_t)0x00000002)
> +#define FGP_CREAT		((__force fgf_t)0x00000004)
> +#define FGP_WRITE		((__force fgf_t)0x00000008)
> +#define FGP_NOFS		((__force fgf_t)0x00000010)
> +#define FGP_NOWAIT		((__force fgf_t)0x00000020)
> +#define FGP_FOR_MMAP		((__force fgf_t)0x00000040)
> +#define FGP_STABLE		((__force fgf_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);
> +		fgf_t fgp_flags, gfp_t gfp);
>  struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
> -		int fgp_flags, gfp_t gfp);
> +		fgf_t fgp_flags, gfp_t gfp);
>  
>  /**
>   * filemap_get_folio - Find and get a folio.
> @@ -590,7 +616,7 @@ 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, fgf_t fgp_flags)
>  {
>  	return pagecache_get_page(mapping, offset, fgp_flags, 0);
>  }
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 9e44a49bbd74..8a669fecfd1c 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -1855,30 +1855,15 @@ 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)
> +		fgf_t fgp_flags, gfp_t gfp)
>  {
>  	struct folio *folio;
>  
> diff --git a/mm/folio-compat.c b/mm/folio-compat.c
> index c6f056c20503..10c3247542cb 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)
> +		fgf_t fgp_flags, gfp_t gfp)
>  {
>  	struct folio *folio;
>  
> -- 
> 2.39.2
>