Commit d30a1100 authored by Wu Fengguang's avatar Wu Fengguang Committed by Linus Torvalds
Browse files

readahead: record mmap read-around states in file_ra_state 



Mmap read-around now shares the same code style and data structure with
readahead code.

This also removes do_page_cache_readahead().  Its last user, mmap
read-around, has been changed to call ra_submit().

The no-readahead-if-congested logic is dumped by the way.  Users will be
pretty sensitive about the slow loading of executables.  So it's
unfavorable to disabled mmap read-around on a congested queue.

[akpm@linux-foundation.org: coding-style fixes]
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: default avatarFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Ying Han <yinghan@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2fad6f5d

include/linux/mm.h

+3 −2
Original line number Diff line number Diff line
@@ -1178,8 +1178,6 @@ void task_dirty_inc(struct task_struct *tsk); 
#define VM_MAX_READAHEAD	128	/* kbytes */

#define VM_MIN_READAHEAD	16	/* kbytes (includes current page) */



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

			pgoff_t offset, unsigned long nr_to_read);

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

			pgoff_t offset, unsigned long nr_to_read);
@@ -1197,6 +1195,9 @@ void page_cache_async_readahead(struct address_space *mapping, 
				unsigned long size);



unsigned long max_sane_readahead(unsigned long nr);

unsigned long ra_submit(struct file_ra_state *ra,

			struct address_space *mapping,

			struct file *filp);



/* Do stack extension */

extern int expand_stack(struct vm_area_struct *vma, unsigned long address);

mm/filemap.c

+7 −5
Original line number Diff line number Diff line
@@ -1488,13 +1488,15 @@ static void do_sync_mmap_readahead(struct vm_area_struct *vma, 
	if (ra->mmap_miss > MMAP_LOTSAMISS)

		return;



	/*

	 * mmap read-around

	 */

	ra_pages = max_sane_readahead(ra->ra_pages);

	if (ra_pages) {

		pgoff_t start = 0;



		if (offset > ra_pages / 2)

			start = offset - ra_pages / 2;

		do_page_cache_readahead(mapping, file, start, ra_pages);

		ra->start = max_t(long, 0, offset - ra_pages/2);

		ra->size = ra_pages;

		ra->async_size = 0;

		ra_submit(ra, mapping, file);

	}

}

mm/readahead.c

+2 −21
Original line number Diff line number Diff line
@@ -133,15 +133,12 @@ out: 
}



/*

 * do_page_cache_readahead actually reads a chunk of disk.  It allocates all

 * __do_page_cache_readahead() actually reads a chunk of disk.  It allocates all

 * the pages first, then submits them all for I/O. This avoids the very bad

 * behaviour which would occur if page allocations are causing VM writeback.

 * We really don't want to intermingle reads and writes like that.

 *

 * Returns the number of pages requested, or the maximum amount of I/O allowed.

 *

 * do_page_cache_readahead() returns -1 if it encountered request queue

 * congestion.

 */

static int

__do_page_cache_readahead(struct address_space *mapping, struct file *filp,
@@ -231,22 +228,6 @@ int force_page_cache_readahead(struct address_space *mapping, struct file *filp, 
	return ret;

}



/*

 * This version skips the IO if the queue is read-congested, and will tell the

 * block layer to abandon the readahead if request allocation would block.

 *

 * force_page_cache_readahead() will ignore queue congestion and will block on

 * request queues.

 */

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

			pgoff_t offset, unsigned long nr_to_read)

{

	if (bdi_read_congested(mapping->backing_dev_info))

		return -1;



	return __do_page_cache_readahead(mapping, filp, offset, nr_to_read, 0);

}



/*

 * Given a desired number of PAGE_CACHE_SIZE readahead pages, return a

 * sensible upper limit.
@@ -260,7 +241,7 @@ unsigned long max_sane_readahead(unsigned long nr) 
/*

 * Submit IO for the read-ahead request in file_ra_state.

 */

static unsigned long ra_submit(struct file_ra_state *ra,

unsigned long ra_submit(struct file_ra_state *ra,

		       struct address_space *mapping, struct file *filp)

{

	int actual;

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