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authorChristoph Lameter <clameter@sgi.com>2006-05-01 12:16:08 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-05-01 18:17:45 -0700
commit4c28f81193b6778f7b49090930d88e6d12bcb928 (patch)
tree5e0d83368e7282060b8de5e73f13eb6003e99391 /mm
parenta4b741e380cb56045ccea36f2dbc10e42af21f24 (diff)
downloadlinux-stericsson-4c28f81193b6778f7b49090930d88e6d12bcb928.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>
Diffstat (limited to 'mm')
-rw-r--r--mm/migrate.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index d444229f2599..1c25040693d2 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -439,6 +439,17 @@ 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