From 7ef0d7377cb287e08f3ae94cebc919448e1f5dff Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Thu, 12 Mar 2009 14:31:38 -0700 Subject: fs: new inode i_state corruption fix There was a report of a data corruption http://lkml.org/lkml/2008/11/14/121. There is a script included to reproduce the problem. During testing, I encountered a number of strange things with ext3, so I tried ext2 to attempt to reduce complexity of the problem. I found that fsstress would quickly hang in wait_on_inode, waiting for I_LOCK to be cleared, even though instrumentation showed that unlock_new_inode had already been called for that inode. This points to memory scribble, or synchronisation problme. i_state of I_NEW inodes is not protected by inode_lock because other processes are not supposed to touch them until I_LOCK (and I_NEW) is cleared. Adding WARN_ON(inode->i_state & I_NEW) to sites where we modify i_state revealed that generic_sync_sb_inodes is picking up new inodes from the inode lists and passing them to __writeback_single_inode without waiting for I_NEW. Subsequently modifying i_state causes corruption. In my case it would look like this: CPU0 CPU1 unlock_new_inode() __sync_single_inode() reg <- inode->i_state reg -> reg & ~(I_LOCK|I_NEW) reg <- inode->i_state reg -> inode->i_state reg -> reg | I_SYNC reg -> inode->i_state Non-atomic RMW on CPU1 overwrites CPU0 store and sets I_LOCK|I_NEW again. Fix for this is rather than wait for I_NEW inodes, just skip over them: inodes concurrently being created are not subject to data integrity operations, and should not significantly contribute to dirty memory either. After this change, I'm unable to reproduce any of the added warnings or hangs after ~1hour of running. Previously, the new warnings would start immediately and hang would happen in under 5 minutes. I'm also testing on ext3 now, and so far no problems there either. I don't know whether this fixes the problem reported above, but it fixes a real problem for me. Cc: "Jorge Boncompte [DTI2]" Reported-by: Adrian Hunter Cc: Jan Kara Cc: Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/inode.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'fs/inode.c') diff --git a/fs/inode.c b/fs/inode.c index 913ab2d9a5d1..826fb0b9d1c3 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -359,6 +359,7 @@ static int invalidate_list(struct list_head *head, struct list_head *dispose) invalidate_inode_buffers(inode); if (!atomic_read(&inode->i_count)) { list_move(&inode->i_list, dispose); + WARN_ON(inode->i_state & I_NEW); inode->i_state |= I_FREEING; count++; continue; @@ -460,6 +461,7 @@ static void prune_icache(int nr_to_scan) continue; } list_move(&inode->i_list, &freeable); + WARN_ON(inode->i_state & I_NEW); inode->i_state |= I_FREEING; nr_pruned++; } @@ -656,6 +658,7 @@ void unlock_new_inode(struct inode *inode) * just created it (so there can be no old holders * that haven't tested I_LOCK). */ + WARN_ON((inode->i_state & (I_LOCK|I_NEW)) != (I_LOCK|I_NEW)); inode->i_state &= ~(I_LOCK|I_NEW); wake_up_inode(inode); } @@ -1145,6 +1148,7 @@ void generic_delete_inode(struct inode *inode) list_del_init(&inode->i_list); list_del_init(&inode->i_sb_list); + WARN_ON(inode->i_state & I_NEW); inode->i_state |= I_FREEING; inodes_stat.nr_inodes--; spin_unlock(&inode_lock); @@ -1186,16 +1190,19 @@ static void generic_forget_inode(struct inode *inode) spin_unlock(&inode_lock); return; } + WARN_ON(inode->i_state & I_NEW); inode->i_state |= I_WILL_FREE; spin_unlock(&inode_lock); write_inode_now(inode, 1); spin_lock(&inode_lock); + WARN_ON(inode->i_state & I_NEW); inode->i_state &= ~I_WILL_FREE; inodes_stat.nr_unused--; hlist_del_init(&inode->i_hash); } list_del_init(&inode->i_list); list_del_init(&inode->i_sb_list); + WARN_ON(inode->i_state & I_NEW); inode->i_state |= I_FREEING; inodes_stat.nr_inodes--; spin_unlock(&inode_lock); -- cgit v1.2.3