tmpfs: open a window in shmem_unuse_inode
There are a couple of reasons (patches follow) why it would be good to open a
window for sleep in shmem_unuse_inode, between its search for a matching swap
entry, and its handling of the entry found.
shmem_unuse_inode must then use igrab to hold the inode against deletion in
that window, and its corresponding iput might result in deletion: so it had
better unlock_page before the iput, and might as well release the page too.
Nor is there any need to hold on to shmem_swaplist_mutex once we know we'll
leave the loop. So this unwinding moves from try_to_unuse and shmem_unuse
into shmem_unuse_inode, in the case when it finds a match.
Let try_to_unuse break on error in the shmem_unuse case, as it does in the
unuse_mm case: though at this point in the series, no error to break on.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 14bc4f2..eade24d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -814,7 +814,7 @@
atomic_inc(&new_start_mm->mm_users);
atomic_inc(&prev_mm->mm_users);
spin_lock(&mmlist_lock);
- while (*swap_map > 1 && !retval &&
+ while (*swap_map > 1 && !retval && !shmem &&
(p = p->next) != &start_mm->mmlist) {
mm = list_entry(p, struct mm_struct, mmlist);
if (!atomic_inc_not_zero(&mm->mm_users))
@@ -846,6 +846,13 @@
mmput(start_mm);
start_mm = new_start_mm;
}
+ if (shmem) {
+ /* page has already been unlocked and released */
+ if (shmem > 0)
+ continue;
+ retval = shmem;
+ break;
+ }
if (retval) {
unlock_page(page);
page_cache_release(page);
@@ -884,12 +891,6 @@
* read from disk into another page. Splitting into two
* pages would be incorrect if swap supported "shared
* private" pages, but they are handled by tmpfs files.
- *
- * Note shmem_unuse already deleted a swappage from
- * the swap cache, unless the move to filepage failed:
- * in which case it left swappage in cache, lowered its
- * swap count to pass quickly through the loops above,
- * and now we must reincrement count to try again later.
*/
if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
struct writeback_control wbc = {
@@ -900,12 +901,8 @@
lock_page(page);
wait_on_page_writeback(page);
}
- if (PageSwapCache(page)) {
- if (shmem)
- swap_duplicate(entry);
- else
- delete_from_swap_cache(page);
- }
+ if (PageSwapCache(page))
+ delete_from_swap_cache(page);
/*
* So we could skip searching mms once swap count went