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Commit bab1d944 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Al Viro
Browse files

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: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 5229645b

fs/inode.c

+14 −18
Original line number Diff line number Diff line
@@ -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;

}