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[PATCH] Updates for page migration

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This adds some additional comments in order to help others figure out how
exactly the code works.  And fix a variable name.

Also swap_page does need to ignore all reference bits when unmapping a
page.  Otherwise we may have to repeatedly unmap a frequently touched page.
So change the try_to_unmap parameter to 1.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Christoph Lameter 2006-02-10 01:51:15 -08:00 committed by Linus Torvalds
parent 8977d929e4
commit 418aade459
1 changed files with 20 additions and 5 deletions
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25
mm/vmscan.c
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@ -632,7 +632,7 @@ static int swap_page(struct page *page)
struct address_space *mapping = page_mapping(page);
if (page_mapped(page) && mapping)
if (try_to_unmap(page, 0) != SWAP_SUCCESS)
if (try_to_unmap(page, 1) != SWAP_SUCCESS)
goto unlock_retry;
if (PageDirty(page)) {
@ -839,7 +839,7 @@ EXPORT_SYMBOL(migrate_page);
* pages are swapped out.
*
* The function returns after 10 attempts or if no pages
* are movable anymore because t has become empty
* are movable anymore because to has become empty
* or no retryable pages exist anymore.
*
* Return: Number of pages not migrated when "to" ran empty.
@ -928,12 +928,21 @@ redo:
goto unlock_both;
if (mapping->a_ops->migratepage) {
/*
* Most pages have a mapping and most filesystems
* should provide a migration function. Anonymous
* pages are part of swap space which also has its
* own migration function. This is the most common
* path for page migration.
*/
rc = mapping->a_ops->migratepage(newpage, page);
goto unlock_both;
}
/*
* Trigger writeout if page is dirty
* Default handling if a filesystem does not provide
* a migration function. We can only migrate clean
* pages so try to write out any dirty pages first.
*/
if (PageDirty(page)) {
switch (pageout(page, mapping)) {
@ -949,9 +958,10 @@ redo:
; /* try to migrate the page below */
}
}
/*
* If we have no buffer or can release the buffer
* then do a simple migration.
* Buffers are managed in a filesystem specific way.
* We must have no buffers or drop them.
*/
if (!page_has_buffers(page) ||
try_to_release_page(page, GFP_KERNEL)) {
@ -966,6 +976,11 @@ redo:
* swap them out.
*/
if (pass > 4) {
/*
* Persistently unable to drop buffers..... As a
* measure of last resort we fall back to
* swap_page().
*/
unlock_page(newpage);
newpage = NULL;
rc = swap_page(page);