From bab1d9444d9a147f1dc3478dd06c16f490227f3e Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 15 Mar 2011 21:51:24 +0100 Subject: prune back iprune_sem iprune_sem is continously giving us lockdep warnings because we do take it in read mode in the reclaim path, but we're also doing non-NOFS allocations under it taken in write mode. Taking a bit deeper look at it I think it's fixable quite trivially: - for invalidate_inodes we do not need iprune_sem at all. We have an active reference on the superblock, so the filesystem is not going away until it has finished. - for evict_inodes we do need it, to make sure prune_icache has done it's work before we tear down the superblock. But there is no reason to hold it over the actual reclaim operation - it's enough to cycle through it after the actual reclaim to make sure we wait for any pending prune_icache to complete. We just have to remove the WARN_ON for otherwise busy inodes as they can actually happen now. Signed-off-by: Christoph Hellwig Signed-off-by: Al Viro --- fs/inode.c | 32 ++++++++++++++------------------ 1 file changed, 14 insertions(+), 18 deletions(-) diff --git a/fs/inode.c b/fs/inode.c index 0647d80accf6..9910c039f026 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -84,16 +84,13 @@ static struct hlist_head *inode_hashtable __read_mostly; DEFINE_SPINLOCK(inode_lock); /* - * iprune_sem provides exclusion between the kswapd or try_to_free_pages - * icache shrinking path, and the umount path. Without this exclusion, - * by the time prune_icache calls iput for the inode whose pages it has - * been invalidating, or by the time it calls clear_inode & destroy_inode - * from its final dispose_list, the struct super_block they refer to - * (for inode->i_sb->s_op) may already have been freed and reused. + * iprune_sem provides exclusion between the icache shrinking and the + * umount path. * - * We make this an rwsem because the fastpath is icache shrinking. In - * some cases a filesystem may be doing a significant amount of work in - * its inode reclaim code, so this should improve parallelism. + * We don't actually need it to protect anything in the umount path, + * but only need to cycle through it to make sure any inode that + * prune_icache took off the LRU list has been fully torn down by the + * time we are past evict_inodes. */ static DECLARE_RWSEM(iprune_sem); @@ -516,17 +513,12 @@ void evict_inodes(struct super_block *sb) struct inode *inode, *next; LIST_HEAD(dispose); - down_write(&iprune_sem); - spin_lock(&inode_lock); list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) { if (atomic_read(&inode->i_count)) continue; - - if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) { - WARN_ON(1); + if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) continue; - } inode->i_state |= I_FREEING; @@ -542,6 +534,13 @@ void evict_inodes(struct super_block *sb) spin_unlock(&inode_lock); dispose_list(&dispose); + + /* + * Cycle through iprune_sem to make sure any inode that prune_icache + * moved off the list before we took the lock has been fully torn + * down. + */ + down_write(&iprune_sem); up_write(&iprune_sem); } @@ -561,8 +560,6 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty) struct inode *inode, *next; LIST_HEAD(dispose); - down_write(&iprune_sem); - spin_lock(&inode_lock); list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) { if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) @@ -590,7 +587,6 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty) spin_unlock(&inode_lock); dispose_list(&dispose); - up_write(&iprune_sem); return busy; } -- cgit v1.2.3