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authorChristoph Lameter <clameter@sgi.com>2006-05-01 12:16:08 -0700
committerChris Wright <chrisw@sous-sol.org>2006-05-20 15:00:33 -0700
commit1d4532d4d7351b552220d9ef0a1901a33f00ee5f (patch)
treefd7cf31a93ceb6c727eb1e808551501677d17645 /mm
parent75178298c6c807a7274ab48ef9c4d6be7d0114d8 (diff)
downloadlinux-linaro-stable-1d4532d4d7351b552220d9ef0a1901a33f00ee5f.tar.gz
[PATCH] page migration: Fix fallback behavior for dirty pages
Currently we check PageDirty() in order to make the decision to swap out the page. However, the dirty information may be only be contained in the ptes pointing to the page. We need to first unmap the ptes before checking for PageDirty(). If unmap is successful then the page count of the page will also be decreased so that pageout() works properly. This is a fix necessary for 2.6.17. Without this fix we may migrate dirty pages for filesystems without migration functions. Filesystems may keep pointers to dirty pages. Migration of dirty pages can result in the filesystem keeping pointers to freed pages. Unmapping is currently not be separated out from removing all the references to a page and moving the mapping. Therefore try_to_unmap will be called again in migrate_page() if the writeout is successful. However, it wont do anything since the ptes are already removed. The coming updates to the page migration code will restructure the code so that this is no longer necessary. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/vmscan.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4fe7e3aa02e2..1d64dc145295 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -949,6 +949,17 @@ redo:
goto unlock_both;
}
+ /* Make sure the dirty bit is up to date */
+ if (try_to_unmap(page, 1) == SWAP_FAIL) {
+ rc = -EPERM;
+ goto unlock_both;
+ }
+
+ if (page_mapcount(page)) {
+ rc = -EAGAIN;
+ goto unlock_both;
+ }
+
/*
* Default handling if a filesystem does not provide
* a migration function. We can only migrate clean