From 531ad7d58c6476c5856653448b4c7d26427502b4 Mon Sep 17 00:00:00 2001 From: Jaegeuk Kim Date: Tue, 30 Apr 2013 11:33:27 +0900 Subject: f2fs: avoid deadlock during evict after f2fs_gc o Deadlock case #1 Thread 1: - writeback_sb_inodes - do_writepages - f2fs_write_data_pages - write_cache_pages - f2fs_write_data_page - f2fs_balance_fs - wait mutex_lock(gc_mutex) Thread 2: - f2fs_balance_fs - mutex_lock(gc_mutex) - f2fs_gc - f2fs_iget - wait iget_locked(inode->i_lock) Thread 3: - do_unlinkat - iput - lock(inode->i_lock) - evict - inode_wait_for_writeback o Deadlock case #2 Thread 1: - __writeback_single_inode : set I_SYNC - do_writepages - f2fs_write_data_page - f2fs_balance_fs - f2fs_gc - iput - evict - inode_wait_for_writeback(I_SYNC) In order to avoid this, even though iput is called with the zero-reference count, we need to stop the eviction procedure if the inode is on writeback. So this patch links f2fs_drop_inode which checks the I_SYNC flag. Signed-off-by: Jaegeuk Kim --- fs/f2fs/super.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'fs/f2fs/super.c') diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c index 5835aaf2fe2..cd0e89a1ff8 100644 --- a/fs/f2fs/super.c +++ b/fs/f2fs/super.c @@ -98,6 +98,20 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb) return &fi->vfs_inode; } +static int f2fs_drop_inode(struct inode *inode) +{ + /* + * This is to avoid a deadlock condition like below. + * writeback_single_inode(inode) + * - f2fs_write_data_page + * - f2fs_gc -> iput -> evict + * - inode_wait_for_writeback(inode) + */ + if (!inode_unhashed(inode) && inode->i_state & I_SYNC) + return 0; + return generic_drop_inode(inode); +} + static void f2fs_i_callback(struct rcu_head *head) { struct inode *inode = container_of(head, struct inode, i_rcu); @@ -232,6 +246,7 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root) static struct super_operations f2fs_sops = { .alloc_inode = f2fs_alloc_inode, + .drop_inode = f2fs_drop_inode, .destroy_inode = f2fs_destroy_inode, .write_inode = f2fs_write_inode, .show_options = f2fs_show_options, -- cgit v1.2.3-70-g09d2