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readahead: record mmap read-around states in file_ra_state

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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.

[[email protected]: coding-style fixes]
Cc: Nick Piggin <[email protected]>
Signed-off-by: Fengguang Wu <[email protected]>
Cc: Ying Han <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Wu Fengguang 2009-06-16 15:31:30 -07:00 • committed by Linus Torvalds
commit d30a11004e
3 changed files with 12 additions and 28 deletions
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23
mm/readahead.c
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@ -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;