fs: factor inode disposal

We have a couple of places that dispose of inodes. factor the
disposal into evict() to isolate this code and make it simpler to
peel away the inode_lock from the code.

While doing this, change the logic flow in iput_final() to separate
the different cases that need to be handled to make the transitions
the inode goes through more obvious.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 41 insertions, 63 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 14b12c4ee026..f752a959254b 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -423,17 +423,6 @@ void __insert_inode_hash(struct inode *inode, unsigned long hashval)
 EXPORT_SYMBOL(__insert_inode_hash);
 
 /**
- *      __remove_inode_hash - remove an inode from the hash
- *      @inode: inode to unhash
- *
- *      Remove an inode from the superblock.
- */
-static void __remove_inode_hash(struct inode *inode)
-{
-        hlist_del_init(&inode->i_hash);
-}
-
-/**
  *      remove_inode_hash - remove an inode from the hash
  *      @inode: inode to unhash
  *
@@ -462,10 +451,31 @@ void end_writeback(struct inode *inode)
 }
 EXPORT_SYMBOL(end_writeback);
 
+/*
+ * Free the inode passed in, removing it from the lists it is still connected
+ * to. We remove any pages still attached to the inode and wait for any IO that
+ * is still in progress before finally destroying the inode.
+ *
+ * An inode must already be marked I_FREEING so that we avoid the inode being
+ * moved back onto lists if we race with other code that manipulates the lists
+ * (e.g. writeback_single_inode). The caller is responsible for setting this.
+ *
+ * An inode must already be removed from the LRU list before being evicted from
+ * the cache. This should occur atomically with setting the I_FREEING state
+ * flag, so no inodes here should ever be on the LRU when being evicted.
+ */
 static void evict(struct inode *inode)
 {
         const struct super_operations *op = inode->i_sb->s_op;
 
+        BUG_ON(!(inode->i_state & I_FREEING));
+        BUG_ON(!list_empty(&inode->i_lru));
+
+        spin_lock(&inode_lock);
+        list_del_init(&inode->i_wb_list);
+        __inode_sb_list_del(inode);
+        spin_unlock(&inode_lock);
+
         if (op->evict_inode) {
                 op->evict_inode(inode);
         } else {
@@ -477,6 +487,15 @@ static void evict(struct inode *inode)
                 bd_forget(inode);
         if (S_ISCHR(inode->i_mode) && inode->i_cdev)
                 cd_forget(inode);
+
+        remove_inode_hash(inode);
+
+        spin_lock(&inode->i_lock);
+        wake_up_bit(&inode->i_state, __I_NEW);
+        BUG_ON(inode->i_state != (I_FREEING | I_CLEAR));
+        spin_unlock(&inode->i_lock);
+
+        destroy_inode(inode);
 }
 
 /*
@@ -495,16 +514,6 @@ static void dispose_list(struct list_head *head)
                 list_del_init(&inode->i_lru);
 
                 evict(inode);
-
-                spin_lock(&inode_lock);
-                __remove_inode_hash(inode);
-                __inode_sb_list_del(inode);
-                spin_unlock(&inode_lock);
-
-                spin_lock(&inode->i_lock);
-                wake_up_bit(&inode->i_state, __I_NEW);
-                spin_unlock(&inode->i_lock);
-                destroy_inode(inode);
         }
 }
 
@@ -537,13 +546,7 @@ void evict_inodes(struct super_block *sb)
                 if (!(inode->i_state & (I_DIRTY | I_SYNC)))
                         inodes_stat.nr_unused--;
                 spin_unlock(&inode->i_lock);
-
-                /*
-                 * Move the inode off the IO lists and LRU once I_FREEING is
-                 * set so that it won't get moved back on there if it is dirty.
-                 */
                 list_move(&inode->i_lru, &dispose);
-                list_del_init(&inode->i_wb_list);
         }
         spin_unlock(&inode_lock);
 
@@ -596,13 +599,7 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty)
                 if (!(inode->i_state & (I_DIRTY | I_SYNC)))
                         inodes_stat.nr_unused--;
                 spin_unlock(&inode->i_lock);
-
-                /*
-                 * Move the inode off the IO lists and LRU once I_FREEING is
-                 * set so that it won't get moved back on there if it is dirty.
-                 */
                 list_move(&inode->i_lru, &dispose);
-                list_del_init(&inode->i_wb_list);
         }
         spin_unlock(&inode_lock);
 
@@ -699,12 +696,7 @@ static void prune_icache(int nr_to_scan)
                 inode->i_state |= I_FREEING;
                 spin_unlock(&inode->i_lock);
 
-                /*
-                 * Move the inode off the IO lists and LRU once I_FREEING is
-                 * set so that it won't get moved back on there if it is dirty.
-                 */
                 list_move(&inode->i_lru, &freeable);
-                list_del_init(&inode->i_wb_list);
                 inodes_stat.nr_unused--;
         }
         if (current_is_kswapd())
@@ -1434,16 +1426,16 @@ static void iput_final(struct inode *inode)
         else
                 drop = generic_drop_inode(inode);
 
+        if (!drop && (sb->s_flags & MS_ACTIVE)) {
+                inode->i_state |= I_REFERENCED;
+                if (!(inode->i_state & (I_DIRTY|I_SYNC)))
+                        inode_lru_list_add(inode);
+                spin_unlock(&inode->i_lock);
+                spin_unlock(&inode_lock);
+                return;
+        }
+
         if (!drop) {
-                if (sb->s_flags & MS_ACTIVE) {
-                        inode->i_state |= I_REFERENCED;
-                        if (!(inode->i_state & (I_DIRTY|I_SYNC))) {
-                                inode_lru_list_add(inode);
-                        }
-                        spin_unlock(&inode->i_lock);
-                        spin_unlock(&inode_lock);
-                        return;
-                }
                 inode->i_state |= I_WILL_FREE;
                 spin_unlock(&inode->i_lock);
                 spin_unlock(&inode_lock);
@@ -1452,28 +1444,14 @@ static void iput_final(struct inode *inode)
                 spin_lock(&inode->i_lock);
                 WARN_ON(inode->i_state & I_NEW);
                 inode->i_state &= ~I_WILL_FREE;
-                __remove_inode_hash(inode);
         }
 
         inode->i_state |= I_FREEING;
-        spin_unlock(&inode->i_lock);
-
-        /*
-         * Move the inode off the IO lists and LRU once I_FREEING is
-         * set so that it won't get moved back on there if it is dirty.
-         */
         inode_lru_list_del(inode);
-        list_del_init(&inode->i_wb_list);
-
-        __inode_sb_list_del(inode);
+        spin_unlock(&inode->i_lock);
         spin_unlock(&inode_lock);
+
         evict(inode);
-        remove_inode_hash(inode);
-        spin_lock(&inode->i_lock);
-        wake_up_bit(&inode->i_state, __I_NEW);
-        BUG_ON(inode->i_state != (I_FREEING | I_CLEAR));
-        spin_unlock(&inode->i_lock);
-        destroy_inode(inode);
 }
 
 /**