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.
Cc: Nick Piggin <npiggin@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Fengguang Wu <wfg@xxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 5 +++--
mm/filemap.c | 12 +++++++-----
mm/readahead.c | 23 ++---------------------
3 files changed, 12 insertions(+), 28 deletions(-)
--- mm.orig/mm/filemap.c
+++ mm/mm/filemap.c
@@ -1556,13 +1556,15 @@ static void do_sync_mmap_readahead(struc
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.orig/include/linux/mm.h
+++ mm/include/linux/mm.h
@@ -1183,8 +1183,6 @@ void task_dirty_inc(struct task_struct *
#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);
@@ -1202,6 +1200,9 @@ void page_cache_async_readahead(struct a
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.orig/mm/readahead.c
+++ mm/mm/readahead.c
@@ -146,15 +146,12 @@ 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,
@@ -245,22 +242,6 @@ int force_page_cache_readahead(struct ad
}
/*
- * 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.
*/
@@ -285,7 +266,7 @@ subsys_initcall(readahead_init);
/*
* 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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