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tmpfs: open a window in shmem_unuse_inode

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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>
This commit is contained in:
Hugh Dickins
2008-02-04 22:28:53 -08:00
committed by Linus Torvalds
parent cb5f7b9a47
commit 2e0e26c76a
2 changed files with 45 additions and 35 deletions
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23
mm/swapfile.c
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@ -814,7 +814,7 @@ static int try_to_unuse(unsigned int type)
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 @@ static int try_to_unuse(unsigned int type)
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 @@ static int try_to_unuse(unsigned int type)
* 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 @@ static int try_to_unuse(unsigned int type)
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