Messages in this thread | | | Subject | Re: [RFC][PATCH 2/2] readahead: avoid page-by-page reads on POSIX_FADV_RANDOM | From | Andi Kleen <> | Date | Wed, 30 Dec 2009 19:02:38 +0100 |
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Wu Fengguang <fengguang.wu@intel.com> writes: > * the ra fields can be accessed concurrently in a racy way. > --- linux.orig/mm/fadvise.c 2009-12-30 13:02:03.000000000 +0800 > +++ linux/mm/fadvise.c 2009-12-30 13:23:05.000000000 +0800 > @@ -77,12 +77,14 @@ SYSCALL_DEFINE(fadvise64_64)(int fd, lof > switch (advice) { > case POSIX_FADV_NORMAL: > file->f_ra.ra_pages = bdi->ra_pages; > + file->f_ra.flags &= ~RA_FLAG_RANDOM; > break; > case POSIX_FADV_RANDOM: > - file->f_ra.ra_pages = 0; > + file->f_ra.flags |= RA_FLAG_RANDOM;
What prevents this from racing with a parallel readahead state modification, losing the bits?
-Andi
-- ak@linux.intel.com -- Speaking for myself only.
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