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-rw-r--r--include/linux/fs.h3
-rw-r--r--mm/fadvise.c10
-rw-r--r--mm/readahead.c6
3 files changed, 18 insertions, 1 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 45689621a851..be87edcaba06 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -87,6 +87,9 @@ struct inodes_stat_t {
*/
#define FMODE_NOCMTIME ((__force fmode_t)2048)
+/* Expect random access pattern */
+#define FMODE_RANDOM ((__force fmode_t)4096)
+
/*
* The below are the various read and write types that we support. Some of
* them include behavioral modifiers that send information down to the
diff --git a/mm/fadvise.c b/mm/fadvise.c
index e43359214f6f..8d723c9e8b75 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -77,12 +77,20 @@ SYSCALL_DEFINE(fadvise64_64)(int fd, loff_t offset, loff_t len, int advice)
switch (advice) {
case POSIX_FADV_NORMAL:
file->f_ra.ra_pages = bdi->ra_pages;
+ spin_lock(&file->f_lock);
+ file->f_mode &= ~FMODE_RANDOM;
+ spin_unlock(&file->f_lock);
break;
case POSIX_FADV_RANDOM:
- file->f_ra.ra_pages = 0;
+ spin_lock(&file->f_lock);
+ file->f_mode |= FMODE_RANDOM;
+ spin_unlock(&file->f_lock);
break;
case POSIX_FADV_SEQUENTIAL:
file->f_ra.ra_pages = bdi->ra_pages * 2;
+ spin_lock(&file->f_lock);
+ file->f_mode &= ~FMODE_RANDOM;
+ spin_unlock(&file->f_lock);
break;
case POSIX_FADV_WILLNEED:
if (!mapping->a_ops->readpage) {
diff --git a/mm/readahead.c b/mm/readahead.c
index 033bc135a41f..337b20e946f6 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -501,6 +501,12 @@ void page_cache_sync_readahead(struct address_space *mapping,
if (!ra->ra_pages)
return;
+ /* be dumb */
+ if (filp->f_mode & FMODE_RANDOM) {
+ force_page_cache_readahead(mapping, filp, offset, req_size);
+ return;
+ }
+
/* do read-ahead */
ondemand_readahead(mapping, ra, filp, false, offset, req_size);
}