Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d8983910a4045fa21022cfccf76ed13eb40fd7f5
Commit:     d8983910a4045fa21022cfccf76ed13eb40fd7f5
Parent:     431a4820bfcdf7ff530e745230bafb06c9bf2d6d
Author:     Fengguang Wu <[EMAIL PROTECTED]>
AuthorDate: Thu Jul 19 01:48:06 2007 -0700
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Thu Jul 19 10:04:44 2007 -0700

    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 <[EMAIL PROTECTED]>
    Cc: Jens Axboe <[EMAIL PROTECTED]>
    Cc: Rusty Russell <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 fs/splice.c |   12 +++++-------
 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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