shmem_writepage() call igrab() on the inode for the page which is came from
reclaimer to add it later into shmem_swaplist for swap-unuse operation.
This igrab() can race with super-block deactivating process:
shrink_inactive_list() deactivate_super()
pageout() tmpfs_fs_type->kill_sb()
shmem_writepage() kill_litter_super()
generic_shutdown_super()
evict_inodes()
igrab()
atomic_read(&inode->i_count)
skip-inode
iput()
if (!list_empty(&sb->s_inodes))
printk("VFS: Busy inodes after...
To avoid this race after this patch shmem_writepage() also try grab sb->s_active.
If sb->s_active == 0 adding to the shmem_swaplist not required, because
super-block deactivation in progress and swap-entries will be released soon.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
---
mm/shmem.c | 9 ++++++++-
1 files changed, 8 insertions(+), 1 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 58da7c1..1f49c03 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1038,11 +1038,13 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
struct address_space *mapping;
unsigned long index;
struct inode *inode;
+ struct super_block *sb;
BUG_ON(!PageLocked(page));
mapping = page->mapping;
index = page->index;
inode = mapping->host;
+ sb = inode->i_sb;
info = SHMEM_I(inode);
if (info->flags & VM_LOCKED)
goto redirty;
@@ -1083,7 +1085,10 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
delete_from_page_cache(page);
shmem_swp_set(info, entry, swap.val);
shmem_swp_unmap(entry);
- if (list_empty(&info->swaplist))
+ if (!list_empty(&info->swaplist) ||
+ !atomic_inc_not_zero(&sb->s_active))
+ sb = NULL;
+ if (sb)
inode = igrab(inode);
else
inode = NULL;
@@ -1098,6 +1103,8 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
mutex_unlock(&shmem_swaplist_mutex);
iput(inode);
}
+ if (sb)
+ deactivate_super(sb);
return 0;
}
--
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