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mm/filemap.c: rewrite pagecache_get_page documentation 

- These were never called PCG flags; they've been called FGP flags since
   their introduction in 2014.
 - The FGP_FOR_MMAP flag was misleadingly documented as if it was an
   alternative to FGP_CREAT instead of an option to it.
 - Rename the 'offset' parameter to 'index'.
 - Capitalisation, formatting, rewording.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Link: http://lkml.kernel.org/r/20200318140253.6141-9-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2020-04-01 21:05:07 -07:00 committed by Linus Torvalds
parent 83daf83788
commit 2294b32e06
1 changed files with 23 additions and 26 deletions
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49
mm/filemap.c
View File

@ -1574,42 +1574,39 @@ struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
EXPORT_SYMBOL(find_lock_entry);
/**
* pagecache_get_page - find and get a page reference
* @mapping: the address_space to search
* @offset: the page index
* @fgp_flags: PCG flags
* @gfp_mask: gfp mask to use for the page cache data page allocation
* pagecache_get_page - Find and get a reference to a page.
* @mapping: The address_space to search.
* @index: The page index.
* @fgp_flags: %FGP flags modify how the page is returned.
* @gfp_mask: Memory allocation flags to use if %FGP_CREAT is specified.
*
* Looks up the page cache slot at @mapping & @offset.
* Looks up the page cache entry at @mapping & @index.
*
* PCG flags modify how the page is returned.
* @fgp_flags can be zero or more of these flags:
*
* @fgp_flags can be:
* * %FGP_ACCESSED - The page will be marked accessed.
* * %FGP_LOCK - The page is returned locked.
* * %FGP_CREAT - If no page is present then a new page is allocated using
* @gfp_mask 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_ACCESSED: the page will be marked accessed
* - FGP_LOCK: Page is return locked
* - FGP_CREAT: If page is not present then a new page is allocated using
* @gfp_mask 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: Similar to FGP_CREAT, only we want to allow the caller to do
* its own locking dance if the page is already in cache, or unlock the page
* before returning if we had to add the page to pagecache.
*
* 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 %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.
*
* Return: the found page or %NULL otherwise.
* Return: The found page or %NULL otherwise.
*/
struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
int fgp_flags, gfp_t gfp_mask)
struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
int fgp_flags, gfp_t gfp_mask)
{
struct page *page;
repeat:
page = find_get_entry(mapping, offset);
page = find_get_entry(mapping, index);
if (xa_is_value(page))
page = NULL;
if (!page)
@ -1631,7 +1628,7 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
put_page(page);
goto repeat;
}
VM_BUG_ON_PAGE(page->index != offset, page);
VM_BUG_ON_PAGE(page->index != index, page);
}
if (fgp_flags & FGP_ACCESSED)
@ -1656,7 +1653,7 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
if (fgp_flags & FGP_ACCESSED)
__SetPageReferenced(page);
err = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
err = add_to_page_cache_lru(page, mapping, index, gfp_mask);
if (unlikely(err)) {
put_page(page);
page = NULL;