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authorChristoph Hellwig <hch@lst.de>2011-03-15 21:51:24 +0100
committerAl Viro <viro@zeniv.linux.org.uk>2011-03-16 09:56:03 -0400
commitbab1d9444d9a147f1dc3478dd06c16f490227f3e (patch)
treee5dd5220c976f604163c0b96945af3ee0be1fe24
parent5229645bdc35f1cc43eb8b25b6993c8fa58b4b43 (diff)
downloadlinux-bab1d9444d9a147f1dc3478dd06c16f490227f3e.tar.bz2
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 <hch@lst.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/inode.c32
1 files 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;
}