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Diffstat (limited to 'mm/readahead.c')
-rw-r--r--mm/readahead.c46
1 files changed, 25 insertions, 21 deletions
diff --git a/mm/readahead.c b/mm/readahead.c
index a7f01fcce9e..ceed7e4790b 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -339,33 +339,25 @@ ondemand_readahead(struct address_space *mapping,
unsigned long req_size)
{
unsigned long max = max_sane_readahead(ra->ra_pages);
- pgoff_t prev_offset;
- int sequential;
+
+ /*
+ * start of file
+ */
+ if (!offset)
+ goto initial_readahead;
/*
* It's the expected callback offset, assume sequential access.
* Ramp up sizes, and push forward the readahead window.
*/
- if (offset && (offset == (ra->start + ra->size - ra->async_size) ||
- offset == (ra->start + ra->size))) {
+ if ((offset == (ra->start + ra->size - ra->async_size) ||
+ offset == (ra->start + ra->size))) {
ra->start += ra->size;
ra->size = get_next_ra_size(ra, max);
ra->async_size = ra->size;
goto readit;
}
- prev_offset = ra->prev_pos >> PAGE_CACHE_SHIFT;
- sequential = offset - prev_offset <= 1UL || req_size > max;
-
- /*
- * Standalone, small read.
- * Read as is, and do not pollute the readahead state.
- */
- if (!hit_readahead_marker && !sequential) {
- return __do_page_cache_readahead(mapping, filp,
- offset, req_size, 0);
- }
-
/*
* Hit a marked page without valid readahead state.
* E.g. interleaved reads.
@@ -391,12 +383,24 @@ ondemand_readahead(struct address_space *mapping,
}
/*
- * It may be one of
- * - first read on start of file
- * - sequential cache miss
- * - oversize random read
- * Start readahead for it.
+ * oversize read
*/
+ if (req_size > max)
+ goto initial_readahead;
+
+ /*
+ * sequential cache miss
+ */
+ if (offset - (ra->prev_pos >> PAGE_CACHE_SHIFT) <= 1UL)
+ goto initial_readahead;
+
+ /*
+ * standalone, small random read
+ * Read as is, and do not pollute the readahead state.
+ */
+ return __do_page_cache_readahead(mapping, filp, offset, req_size, 0);
+
+initial_readahead:
ra->start = offset;
ra->size = get_init_ra_size(req_size, max);
ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size;