writeback: skip new or to-be-freed inodes
1) I_FREEING tests should be coupled with I_CLEAR
The two I_FREEING tests are racy because clear_inode() can set i_state to
I_CLEAR between the clear of I_SYNC and the test of I_FREEING.
2) skip I_WILL_FREE inodes in generic_sync_sb_inodes() to avoid possible
races with generic_forget_inode()
generic_forget_inode() sets I_WILL_FREE call writeback on its own, so
generic_sync_sb_inodes() shall not try to step in and create possible races:
generic_forget_inode
inode->i_state |= I_WILL_FREE;
spin_unlock(&inode_lock);
generic_sync_sb_inodes()
spin_lock(&inode_lock);
__iget(inode);
__writeback_single_inode
// see non zero i_count
may WARN here ==> WARN_ON(inode->i_state & I_WILL_FREE);
spin_unlock(&inode_lock);
may call generic_forget_inode again ==> iput(inode);
The above race and warning didn't turn up because writeback_inodes() holds
the s_umount lock, so generic_forget_inode() finds MS_ACTIVE and returns
early. But we are not sure the UBIFS calls and future callers will
guarantee that. So skip I_WILL_FREE inodes for the sake of safety.
Cc: Eric Sandeen <sandeen@sandeen.net>
Acked-by: Jeff Layton <jlayton@redhat.com>
Cc: Masayoshi MIZUMA <m.mizuma@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Artem Bityutskiy <dedekind1@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Acked-by: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 40308e9..caf0491 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -321,7 +321,7 @@
spin_lock(&inode_lock);
inode->i_state &= ~I_SYNC;
- if (!(inode->i_state & I_FREEING)) {
+ if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
if (!(inode->i_state & I_DIRTY) &&
mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
/*
@@ -492,7 +492,7 @@
break;
}
- if (inode->i_state & I_NEW) {
+ if (inode->i_state & (I_NEW | I_WILL_FREE)) {
requeue_io(inode);
continue;
}
@@ -523,7 +523,7 @@
if (current_is_pdflush() && !writeback_acquire(bdi))
break;
- BUG_ON(inode->i_state & I_FREEING);
+ BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
__iget(inode);
pages_skipped = wbc->pages_skipped;
__writeback_single_inode(inode, wbc);