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-rw-r--r--mm/shmem.c37
1 files changed, 25 insertions, 12 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index 530c5033d02..ee9024483f6 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -833,6 +833,10 @@ static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, s
idx = 0;
ptr = info->i_direct;
spin_lock(&info->lock);
+ if (!info->swapped) {
+ list_del_init(&info->swaplist);
+ goto lost2;
+ }
limit = info->next_index;
size = limit;
if (size > SHMEM_NR_DIRECT)
@@ -894,8 +898,15 @@ found:
inode = igrab(&info->vfs_inode);
spin_unlock(&info->lock);
- /* move head to start search for next from here */
- list_move_tail(&shmem_swaplist, &info->swaplist);
+ /*
+ * Move _head_ to start search for next from here.
+ * But be careful: shmem_delete_inode checks list_empty without taking
+ * mutex, and there's an instant in list_move_tail when info->swaplist
+ * would appear empty, if it were the only one on shmem_swaplist. We
+ * could avoid doing it if inode NULL; or use this minor optimization.
+ */
+ if (shmem_swaplist.next != &info->swaplist)
+ list_move_tail(&shmem_swaplist, &info->swaplist);
mutex_unlock(&shmem_swaplist_mutex);
error = 1;
@@ -955,10 +966,7 @@ int shmem_unuse(swp_entry_t entry, struct page *page)
mutex_lock(&shmem_swaplist_mutex);
list_for_each_safe(p, next, &shmem_swaplist) {
info = list_entry(p, struct shmem_inode_info, swaplist);
- if (info->swapped)
- found = shmem_unuse_inode(info, entry, page);
- else
- list_del_init(&info->swaplist);
+ found = shmem_unuse_inode(info, entry, page);
cond_resched();
if (found)
goto out;
@@ -1021,18 +1029,23 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
remove_from_page_cache(page);
shmem_swp_set(info, entry, swap.val);
shmem_swp_unmap(entry);
+ if (list_empty(&info->swaplist))
+ inode = igrab(inode);
+ else
+ inode = NULL;
spin_unlock(&info->lock);
- if (list_empty(&info->swaplist)) {
- mutex_lock(&shmem_swaplist_mutex);
- /* move instead of add in case we're racing */
- list_move_tail(&info->swaplist, &shmem_swaplist);
- mutex_unlock(&shmem_swaplist_mutex);
- }
swap_duplicate(swap);
BUG_ON(page_mapped(page));
page_cache_release(page); /* pagecache ref */
set_page_dirty(page);
unlock_page(page);
+ if (inode) {
+ mutex_lock(&shmem_swaplist_mutex);
+ /* move instead of add in case we're racing */
+ list_move_tail(&info->swaplist, &shmem_swaplist);
+ mutex_unlock(&shmem_swaplist_mutex);
+ iput(inode);
+ }
return 0;
}