Call posix_fadvise twice to avoid race condition

The kernel tries once to lock the page to be freed. If this fails, it won't be freed. (This happens quite often, actually!)

Call posix_fadvise twice to avoid race condition
ffcf68bb · Julius Plenz · 6f63abc2 · ffcf68bb
Commit ffcf68bb authored Feb 04, 2012 by Julius Plenz
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Showing with 5 additions and 2 deletions

nocache.c nocache.c +5 -2

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--- a/nocache.c
+++ b/nocache.c
@@ -141,9 +141,12 @@ static void free_unclaimed_pages(int fd)
    if(i == _MAX_FDS)
        return; /* not found */

-    for(j = 0; j < fds[i].nr_pages; j++)
-        if(!(fds[i].info[j] & 1))
+    for(j = 0; j < fds[i].nr_pages; j++) {
+        if(!(fds[i].info[j] & 1)) {
            fadv_dontneed(fd, j*PAGESIZE, PAGESIZE);
+            fadv_dontneed(fd, j*PAGESIZE, PAGESIZE);
+        }
+    }

    /* forget written contents that go beyond previous file size */
    fadv_dontneed(fd, fds[i].size, 0);