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authorFengguang Wu <wfg@mail.ustc.edu.cn>2007-07-19 01:48:06 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-19 10:04:44 -0700
commitd8983910a4045fa21022cfccf76ed13eb40fd7f5 (patch)
tree81902a5157ace03a94aa4b62599a20bc87f7a1c0 /fs/splice.c
parent431a4820bfcdf7ff530e745230bafb06c9bf2d6d (diff)
downloadop-kernel-dev-d8983910a4045fa21022cfccf76ed13eb40fd7f5.zip
op-kernel-dev-d8983910a4045fa21022cfccf76ed13eb40fd7f5.tar.gz
readahead: pass real splice size
Pass real splice size to page_cache_readahead_ondemand(). The splice code works in chunks of 16 pages internally. The readahead code should be told of the overall splice size, instead of the internal chunk size. Otherwize bad things may happen. Imagine some 17-page random splice reads. The code before this patch will result in two readahead calls: readahead(16); readahead(1); That leads to one 16-page I/O and one 32-page I/O: one extra I/O and 31 readahead miss pages. Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/splice.c')
-rw-r--r--fs/splice.c12
1 files changed, 5 insertions, 7 deletions
diff --git a/fs/splice.c b/fs/splice.c
index 421b3b8..6ddd032 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -265,7 +265,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
unsigned int flags)
{
struct address_space *mapping = in->f_mapping;
- unsigned int loff, nr_pages;
+ unsigned int loff, nr_pages, req_pages;
struct page *pages[PIPE_BUFFERS];
struct partial_page partial[PIPE_BUFFERS];
struct page *page;
@@ -281,10 +281,8 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
index = *ppos >> PAGE_CACHE_SHIFT;
loff = *ppos & ~PAGE_CACHE_MASK;
- nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
-
- if (nr_pages > PIPE_BUFFERS)
- nr_pages = PIPE_BUFFERS;
+ req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+ nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS);
/*
* Lookup the (hopefully) full range of pages we need.
@@ -298,7 +296,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
*/
if (spd.nr_pages < nr_pages)
page_cache_readahead_ondemand(mapping, &in->f_ra, in,
- NULL, index, nr_pages - spd.nr_pages);
+ NULL, index, req_pages - spd.nr_pages);
error = 0;
while (spd.nr_pages < nr_pages) {
@@ -355,7 +353,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
if (PageReadahead(page))
page_cache_readahead_ondemand(mapping, &in->f_ra, in,
- page, index, nr_pages - page_nr);
+ page, index, req_pages - page_nr);
/*
* If the page isn't uptodate, we may need to start io on it
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