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authorPaul Jackson <pj@sgi.com>2006-05-20 15:00:10 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-05-21 12:59:18 -0700
commit36be57ffe39e03aab9fbe857f70c7a6a15bd9e08 (patch)
tree8062e9a9e49fd942fab35e17a2b5afe571a74f63 /kernel
parent[PATCH] Cpuset: might sleep checking zones allowed fix (diff)
downloadlinux-dev-36be57ffe39e03aab9fbe857f70c7a6a15bd9e08.tar.xz
linux-dev-36be57ffe39e03aab9fbe857f70c7a6a15bd9e08.zip
[PATCH] cpuset: update cpuset_zones_allowed comment
Update the kernel/cpuset.c:cpuset_zone_allowed() comment. The rule for when mm/page_alloc.c should call cpuset_zone_allowed() was intended to be: Don't call cpuset_zone_allowed() if you can't sleep, unless you pass in the __GFP_HARDWALL flag set in gfp_flag, which disables the code that might scan up ancestor cpusets and sleep. The explanation of this rule in the comment above cpuset_zone_allowed() was stale, as a result of a restructuring of some __alloc_pages() code in November 2005. Rewrite that comment ... Signed-off-by: Paul Jackson <pj@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cpuset.c24
1 files changed, 15 insertions, 9 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 72248d1b9e3f..57fd88237afc 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2231,19 +2231,25 @@ static const struct cpuset *nearest_exclusive_ancestor(const struct cpuset *cs)
* So only GFP_KERNEL allocations, if all nodes in the cpuset are
* short of memory, might require taking the callback_mutex mutex.
*
- * The first loop over the zonelist in mm/page_alloc.c:__alloc_pages()
- * calls here with __GFP_HARDWALL always set in gfp_mask, enforcing
- * hardwall cpusets - no allocation on a node outside the cpuset is
- * allowed (unless in interrupt, of course).
- *
- * The second loop doesn't even call here for GFP_ATOMIC requests
- * (if the __alloc_pages() local variable 'wait' is set). That check
- * and the checks below have the combined affect in the second loop of
- * the __alloc_pages() routine that:
+ * The first call here from mm/page_alloc:get_page_from_freelist()
+ * has __GFP_HARDWALL set in gfp_mask, enforcing hardwall cpusets, so
+ * no allocation on a node outside the cpuset is allowed (unless in
+ * interrupt, of course).
+ *
+ * The second pass through get_page_from_freelist() doesn't even call
+ * here for GFP_ATOMIC calls. For those calls, the __alloc_pages()
+ * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
+ * in alloc_flags. That logic and the checks below have the combined
+ * affect that:
* in_interrupt - any node ok (current task context irrelevant)
* GFP_ATOMIC - any node ok
* GFP_KERNEL - any node in enclosing mem_exclusive cpuset ok
* GFP_USER - only nodes in current tasks mems allowed ok.
+ *
+ * Rule:
+ * Don't call cpuset_zone_allowed() if you can't sleep, unless you
+ * pass in the __GFP_HARDWALL flag set in gfp_flag, which disables
+ * the code that might scan up ancestor cpusets and sleep.
**/
int __cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)