Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 7361f4d8 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

[PATCH] readahead commentary 



Add a few comments surrounding the generic readahead API.

Also convert some ulongs into pgoff_t: the identifier for PAGE_CACHE_SIZE
offsets into pagecache.

Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent bf8f972d

include/linux/mm.h

+4 −4
Original line number Diff line number Diff line
@@ -932,13 +932,13 @@ int write_one_page(struct page *page, int wait); 
					 * turning readahead off */



int do_page_cache_readahead(struct address_space *mapping, struct file *filp,

			unsigned long offset, unsigned long nr_to_read);

			pgoff_t offset, unsigned long nr_to_read);

int force_page_cache_readahead(struct address_space *mapping, struct file *filp,

			unsigned long offset, unsigned long nr_to_read);

			pgoff_t offset, unsigned long nr_to_read);

unsigned long page_cache_readahead(struct address_space *mapping,

			  struct file_ra_state *ra,

			  struct file *filp,

			  unsigned long offset,

			  pgoff_t offset,

			  unsigned long size);

void handle_ra_miss(struct address_space *mapping, 

		    struct file_ra_state *ra, pgoff_t offset);

mm/readahead.c

+22 −9
Original line number Diff line number Diff line
@@ -254,7 +254,7 @@ static int read_pages(struct address_space *mapping, struct file *filp, 
 */

static int

__do_page_cache_readahead(struct address_space *mapping, struct file *filp,

			unsigned long offset, unsigned long nr_to_read)

			pgoff_t offset, unsigned long nr_to_read)

{

	struct inode *inode = mapping->host;

	struct page *page;
@@ -274,7 +274,7 @@ __do_page_cache_readahead(struct address_space *mapping, struct file *filp, 
	 */

	read_lock_irq(&mapping->tree_lock);

	for (page_idx = 0; page_idx < nr_to_read; page_idx++) {

		unsigned long page_offset = offset + page_idx;

		pgoff_t page_offset = offset + page_idx;

		

		if (page_offset > end_index)

			break;
@@ -311,7 +311,7 @@ __do_page_cache_readahead(struct address_space *mapping, struct file *filp, 
 * memory at once.

 */

int force_page_cache_readahead(struct address_space *mapping, struct file *filp,

		unsigned long offset, unsigned long nr_to_read)

		pgoff_t offset, unsigned long nr_to_read)

{

	int ret = 0;
@@ -368,7 +368,7 @@ static inline int check_ra_success(struct file_ra_state *ra, 
 * request queues.

 */

int do_page_cache_readahead(struct address_space *mapping, struct file *filp,

			unsigned long offset, unsigned long nr_to_read)

			pgoff_t offset, unsigned long nr_to_read)

{

	if (bdi_read_congested(mapping->backing_dev_info))

		return -1;
@@ -385,7 +385,7 @@ int do_page_cache_readahead(struct address_space *mapping, struct file *filp, 
 */

static int

blockable_page_cache_readahead(struct address_space *mapping, struct file *filp,

			unsigned long offset, unsigned long nr_to_read,

			pgoff_t offset, unsigned long nr_to_read,

			struct file_ra_state *ra, int block)

{

	int actual;
@@ -430,14 +430,27 @@ static int make_ahead_window(struct address_space *mapping, struct file *filp, 
	return ret;

}



/*

 * page_cache_readahead is the main function.  If performs the adaptive

/**

 * page_cache_readahead - generic adaptive readahead

 * @mapping: address_space which holds the pagecache and I/O vectors

 * @ra: file_ra_state which holds the readahead state

 * @filp: passed on to ->readpage() and ->readpages()

 * @offset: start offset into @mapping, in PAGE_CACHE_SIZE units

 * @req_size: hint: total size of the read which the caller is performing in

 *            PAGE_CACHE_SIZE units

 *

 * page_cache_readahead() is the main function.  If performs the adaptive

 * readahead window size management and submits the readahead I/O.

 *

 * Note that @filp is purely used for passing on to the ->readpage[s]()

 * handler: it may refer to a different file from @mapping (so we may not use

 * @filp->f_mapping or @filp->f_dentry->d_inode here).

 * Also, @ra may not be equal to &@filp->f_ra.

 *

 */

unsigned long

page_cache_readahead(struct address_space *mapping, struct file_ra_state *ra,

		     struct file *filp, unsigned long offset,

		     unsigned long req_size)

		     struct file *filp, pgoff_t offset, unsigned long req_size)

{

	unsigned long max, newsize;

	int sequential;