From 84a892456046921a40646114deed65e2df93a1bc Mon Sep 17 00:00:00 2001 From: Wu Fengguang Date: Tue, 16 Jun 2009 15:33:17 -0700 Subject: [PATCH] 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 Acked-by: Jeff Layton Cc: Masayoshi MIZUMA Signed-off-by: Wu Fengguang Cc: Artem Bityutskiy Cc: Christoph Hellwig Acked-by: Jan Kara Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/fs-writeback.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 40308e98c6a4..caf049146ca2 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -321,7 +321,7 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc) 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 @@ void generic_sync_sb_inodes(struct super_block *sb, break; } - if (inode->i_state & I_NEW) { + if (inode->i_state & (I_NEW | I_WILL_FREE)) { requeue_io(inode); continue; } @@ -523,7 +523,7 @@ void generic_sync_sb_inodes(struct super_block *sb, 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); -- 2.20.1