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mm/filemap: Add readahead_folio() 

The pointers stored in the page cache are folios, by definition.
This change comes with a behaviour change -- callers of readahead_folio()
are no longer required to put the page reference themselves.  This matches
how readpage works, rather than matching how readpages used to work.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
Matthew Wilcox (Oracle) 2021-04-27 16:37:09 -04:00
parent f705bf84ea
commit 9bf70167e3
1 changed files with 39 additions and 15 deletions
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54
include/linux/pagemap.h
View File

@ -987,33 +987,57 @@ void page_cache_async_readahead(struct address_space *mapping,
page_cache_async_ra(&ractl, page, req_count);
}
static inline struct folio *__readahead_folio(struct readahead_control *ractl)
{
struct folio *folio;
BUG_ON(ractl->_batch_count > ractl->_nr_pages);
ractl->_nr_pages -= ractl->_batch_count;
ractl->_index += ractl->_batch_count;
if (!ractl->_nr_pages) {
ractl->_batch_count = 0;
return NULL;
}
folio = xa_load(&ractl->mapping->i_pages, ractl->_index);
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
ractl->_batch_count = folio_nr_pages(folio);
return folio;
}
/**
* readahead_page - Get the next page to read.
* @rac: The current readahead request.
* @ractl: The current readahead request.
*
* Context: The page is locked and has an elevated refcount. The caller
* should decreases the refcount once the page has been submitted for I/O
* and unlock the page once all I/O to that page has completed.
* Return: A pointer to the next page, or %NULL if we are done.
*/
static inline struct page *readahead_page(struct readahead_control *rac)
static inline struct page *readahead_page(struct readahead_control *ractl)
{
struct page *page;
struct folio *folio = __readahead_folio(ractl);
BUG_ON(rac->_batch_count > rac->_nr_pages);
rac->_nr_pages -= rac->_batch_count;
rac->_index += rac->_batch_count;
return &folio->page;
}
if (!rac->_nr_pages) {
rac->_batch_count = 0;
return NULL;
}
/**
* readahead_folio - Get the next folio to read.
* @ractl: The current readahead request.
*
* Context: The folio is locked. The caller should unlock the folio once
* all I/O to that folio has completed.
* Return: A pointer to the next folio, or %NULL if we are done.
*/
static inline struct folio *readahead_folio(struct readahead_control *ractl)
{
struct folio *folio = __readahead_folio(ractl);
page = xa_load(&rac->mapping->i_pages, rac->_index);
VM_BUG_ON_PAGE(!PageLocked(page), page);
rac->_batch_count = thp_nr_pages(page);
return page;
if (folio)
folio_put(folio);
return folio;
}
static inline unsigned int __readahead_batch(struct readahead_control *rac,