[patch 07/35] fs: icache lock i_state

[npiggin@kernel.dk]

[-- Attachment #1: fs-inode_lock-scale-3.patch --]
[-- Type: text/plain, Size: 17388 bytes --]

Protect i_state updates with i_lock

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

---
 fs/drop_caches.c       |    9 +++--
 fs/fs-writeback.c      |   35 +++++++++++++++++---
 fs/inode.c             |   83 ++++++++++++++++++++++++++++++++++++++++++-------
 fs/notify/inode_mark.c |   23 +++++++++----
 fs/quota/dquot.c       |   28 ++++++++++++++--
 5 files changed, 148 insertions(+), 30 deletions(-)

Index: linux-2.6/fs/drop_caches.c
===================================================================
--- linux-2.6.orig/fs/drop_caches.c	2010-10-19 14:18:58.000000000 +1100
+++ linux-2.6/fs/drop_caches.c	2010-10-19 14:19:32.000000000 +1100
@@ -19,11 +19,14 @@
 	spin_lock(&inode_lock);
 	spin_lock(&sb_inode_list_lock);
 	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
-		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
-			continue;
-		if (inode->i_mapping->nrpages == 0)
+		spin_lock(&inode->i_lock);
+		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)
+				|| inode->i_mapping->nrpages == 0) {
+			spin_unlock(&inode->i_lock);
 			continue;
+		}
 		__iget(inode);
+		spin_unlock(&inode->i_lock);
 		spin_unlock(&sb_inode_list_lock);
 		spin_unlock(&inode_lock);
 		invalidate_mapping_pages(inode->i_mapping, 0, -1);
Index: linux-2.6/fs/fs-writeback.c
===================================================================
--- linux-2.6.orig/fs/fs-writeback.c	2010-10-19 14:18:58.000000000 +1100
+++ linux-2.6/fs/fs-writeback.c	2010-10-19 14:19:36.000000000 +1100
@@ -288,10 +288,12 @@
 	wait_queue_head_t *wqh;
 
 	wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
-	 while (inode->i_state & I_SYNC) {
+	while (inode->i_state & I_SYNC) {
+		spin_unlock(&inode->i_lock);
 		spin_unlock(&inode_lock);
 		__wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
 		spin_lock(&inode_lock);
+		spin_lock(&inode->i_lock);
 	}
 }
 
@@ -345,6 +347,7 @@
 	/* Set I_SYNC, reset I_DIRTY_PAGES */
 	inode->i_state |= I_SYNC;
 	inode->i_state &= ~I_DIRTY_PAGES;
+	spin_unlock(&inode->i_lock);
 	spin_unlock(&inode_lock);
 
 	ret = do_writepages(mapping, wbc);
@@ -366,8 +369,10 @@
 	 * write_inode()
 	 */
 	spin_lock(&inode_lock);
+	spin_lock(&inode->i_lock);
 	dirty = inode->i_state & I_DIRTY;
 	inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
+	spin_unlock(&inode->i_lock);
 	spin_unlock(&inode_lock);
 	/* Don't write the inode if only I_DIRTY_PAGES was set */
 	if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
@@ -377,6 +382,7 @@
 	}
 
 	spin_lock(&inode_lock);
+	spin_lock(&inode->i_lock);
 	inode->i_state &= ~I_SYNC;
 	if (!(inode->i_state & I_FREEING)) {
 		if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
@@ -487,7 +493,9 @@
 			return 0;
 		}
 
+		spin_lock(&inode->i_lock);
 		if (inode->i_state & (I_NEW | I_WILL_FREE)) {
+			spin_unlock(&inode->i_lock);
 			requeue_io(inode);
 			continue;
 		}
@@ -495,8 +503,10 @@
 		 * Was this inode dirtied after sync_sb_inodes was called?
 		 * This keeps sync from extra jobs and livelock.
 		 */
-		if (inode_dirtied_after(inode, wbc->wb_start))
+		if (inode_dirtied_after(inode, wbc->wb_start)) {
+			spin_unlock(&inode->i_lock);
 			return 1;
+		}
 
 		BUG_ON(inode->i_state & I_FREEING);
 		__iget(inode);
@@ -509,6 +519,7 @@
 			 */
 			redirty_tail(inode);
 		}
+		spin_unlock(&inode->i_lock);
 		spin_unlock(&inode_lock);
 		iput(inode);
 		cond_resched();
@@ -944,6 +955,7 @@
 		block_dump___mark_inode_dirty(inode);
 
 	spin_lock(&inode_lock);
+	spin_lock(&inode->i_lock);
 	if ((inode->i_state & flags) != flags) {
 		const int was_dirty = inode->i_state & I_DIRTY;
 
@@ -994,6 +1006,7 @@
 		}
 	}
 out:
+	spin_unlock(&inode->i_lock);
 	spin_unlock(&inode_lock);
 
 	if (wakeup_bdi)
@@ -1041,12 +1054,20 @@
 	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
 		struct address_space *mapping;
 
-		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
+		spin_lock(&inode->i_lock);
+		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
+			spin_unlock(&inode->i_lock);
 			continue;
+		}
+
 		mapping = inode->i_mapping;
-		if (mapping->nrpages == 0)
+		if (mapping->nrpages == 0) {
+			spin_unlock(&inode->i_lock);
 			continue;
-		__iget(inode);
+		}
+
+ 		__iget(inode);
+		spin_unlock(&inode->i_lock);
 		spin_unlock(&sb_inode_list_lock);
 		spin_unlock(&inode_lock);
 		/*
@@ -1173,7 +1194,9 @@
 
 	might_sleep();
 	spin_lock(&inode_lock);
+	spin_lock(&inode->i_lock);
 	ret = writeback_single_inode(inode, &wbc);
+	spin_unlock(&inode->i_lock);
 	spin_unlock(&inode_lock);
 	if (sync)
 		inode_sync_wait(inode);
@@ -1197,7 +1220,9 @@
 	int ret;
 
 	spin_lock(&inode_lock);
+	spin_lock(&inode->i_lock);
 	ret = writeback_single_inode(inode, wbc);
+	spin_unlock(&inode->i_lock);
 	spin_unlock(&inode_lock);
 	return ret;
 }
Index: linux-2.6/fs/inode.c
===================================================================
--- linux-2.6.orig/fs/inode.c	2010-10-19 14:18:58.000000000 +1100
+++ linux-2.6/fs/inode.c	2010-10-19 14:19:37.000000000 +1100
@@ -31,10 +31,13 @@
  *   s_inodes, i_sb_list
  * inode_hash_lock protects:
  *   inode hash table, i_hash
+ * inode->i_lock protects:
+ *   i_state
  *
  * Ordering:
  * inode_lock
  *   sb_inode_list_lock
+ *     inode->i_lock
  * inode_lock
  *   inode_hash_lock
  */
@@ -97,7 +100,7 @@
  */
 DEFINE_SPINLOCK(inode_lock);
 DEFINE_SPINLOCK(sb_inode_list_lock);
-DEFINE_SPINLOCK(inode_hash_lock);
+static DEFINE_SPINLOCK(inode_hash_lock);
 
 /*
  * iprune_sem provides exclusion between the kswapd or try_to_free_pages
@@ -296,6 +299,8 @@
  */
 void __iget(struct inode *inode)
 {
+	assert_spin_locked(&inode->i_lock);
+
 	if (atomic_inc_return(&inode->i_count) != 1)
 		return;
 
@@ -396,16 +401,21 @@
 		if (tmp == head)
 			break;
 		inode = list_entry(tmp, struct inode, i_sb_list);
-		if (inode->i_state & I_NEW)
+		spin_lock(&inode->i_lock);
+		if (inode->i_state & I_NEW) {
+			spin_unlock(&inode->i_lock);
 			continue;
+		}
 		invalidate_inode_buffers(inode);
 		if (!atomic_read(&inode->i_count)) {
 			list_move(&inode->i_list, dispose);
 			WARN_ON(inode->i_state & I_NEW);
 			inode->i_state |= I_FREEING;
+			spin_unlock(&inode->i_lock);
 			count++;
 			continue;
 		}
+		spin_unlock(&inode->i_lock);
 		busy = 1;
 	}
 	/* only unused inodes may be cached with i_count zero */
@@ -484,12 +494,15 @@
 
 		inode = list_entry(inode_unused.prev, struct inode, i_list);
 
+		spin_lock(&inode->i_lock);
 		if (inode->i_state || atomic_read(&inode->i_count)) {
 			list_move(&inode->i_list, &inode_unused);
+			spin_unlock(&inode->i_lock);
 			continue;
 		}
 		if (inode_has_buffers(inode) || inode->i_data.nrpages) {
 			__iget(inode);
+			spin_unlock(&inode->i_lock);
 			spin_unlock(&inode_lock);
 			if (remove_inode_buffers(inode))
 				reap += invalidate_mapping_pages(&inode->i_data,
@@ -500,12 +513,16 @@
 			if (inode != list_entry(inode_unused.next,
 						struct inode, i_list))
 				continue;	/* wrong inode or list_empty */
-			if (!can_unuse(inode))
+			spin_lock(&inode->i_lock);
+			if (!can_unuse(inode)) {
+				spin_unlock(&inode->i_lock);
 				continue;
+			}
 		}
 		list_move(&inode->i_list, &freeable);
 		WARN_ON(inode->i_state & I_NEW);
 		inode->i_state |= I_FREEING;
+		spin_unlock(&inode->i_lock);
 		nr_pruned++;
 	}
 	inodes_stat.nr_unused -= nr_pruned;
@@ -577,8 +594,14 @@
 	hlist_for_each_entry(inode, node, head, i_hash) {
 		if (inode->i_sb != sb)
 			continue;
-		if (!test(inode, data))
+		if (!spin_trylock(&inode->i_lock)) {
+			spin_unlock(&inode_hash_lock);
+			goto repeat;
+		}
+		if (!test(inode, data)) {
+			spin_unlock(&inode->i_lock);
 			continue;
+		}
 		if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
 			spin_unlock(&inode_hash_lock);
 			__wait_on_freeing_inode(inode);
@@ -607,6 +630,10 @@
 			continue;
 		if (inode->i_sb != sb)
 			continue;
+		if (!spin_trylock(&inode->i_lock)) {
+			spin_unlock(&inode_hash_lock);
+			goto repeat;
+		}
 		if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
 			spin_unlock(&inode_hash_lock);
 			__wait_on_freeing_inode(inode);
@@ -633,10 +660,10 @@
 			struct inode *inode)
 {
 	inodes_stat.nr_inodes++;
-	list_add(&inode->i_list, &inode_in_use);
 	spin_lock(&sb_inode_list_lock);
 	list_add(&inode->i_sb_list, &sb->s_inodes);
 	spin_unlock(&sb_inode_list_lock);
+	list_add(&inode->i_list, &inode_in_use);
 	if (head) {
 		spin_lock(&inode_hash_lock);
 		hlist_add_head(&inode->i_hash, head);
@@ -693,9 +720,9 @@
 	inode = alloc_inode(sb);
 	if (inode) {
 		spin_lock(&inode_lock);
-		__inode_add_to_lists(sb, NULL, inode);
 		inode->i_ino = ++last_ino;
 		inode->i_state = 0;
+		__inode_add_to_lists(sb, NULL, inode);
 		spin_unlock(&inode_lock);
 	}
 	return inode;
@@ -762,8 +789,8 @@
 			if (set(inode, data))
 				goto set_failed;
 
-			__inode_add_to_lists(sb, head, inode);
 			inode->i_state = I_NEW;
+			__inode_add_to_lists(sb, head, inode);
 			spin_unlock(&inode_lock);
 
 			/* Return the locked inode with I_NEW set, the
@@ -778,6 +805,7 @@
 		 * allocated.
 		 */
 		__iget(old);
+		spin_unlock(&old->i_lock);
 		spin_unlock(&inode_lock);
 		destroy_inode(inode);
 		inode = old;
@@ -786,6 +814,7 @@
 	return inode;
 
 set_failed:
+	spin_unlock(&inode->i_lock);
 	spin_unlock(&inode_lock);
 	destroy_inode(inode);
 	return NULL;
@@ -809,8 +838,8 @@
 		old = find_inode_fast(sb, head, ino);
 		if (!old) {
 			inode->i_ino = ino;
-			__inode_add_to_lists(sb, head, inode);
 			inode->i_state = I_NEW;
+			__inode_add_to_lists(sb, head, inode);
 			spin_unlock(&inode_lock);
 
 			/* Return the locked inode with I_NEW set, the
@@ -825,6 +854,7 @@
 		 * allocated.
 		 */
 		__iget(old);
+		spin_unlock(&old->i_lock);
 		spin_unlock(&inode_lock);
 		destroy_inode(inode);
 		inode = old;
@@ -866,6 +896,7 @@
 		res = counter++;
 		head = inode_hashtable + hash(sb, res);
 		inode = find_inode_fast(sb, head, res);
+		spin_unlock(&inode->i_lock);
 	} while (inode != NULL);
 	spin_unlock(&inode_lock);
 
@@ -875,7 +906,10 @@
 
 struct inode *igrab(struct inode *inode)
 {
+	struct inode *ret = inode;
+
 	spin_lock(&inode_lock);
+	spin_lock(&inode->i_lock);
 	if (!(inode->i_state & (I_FREEING|I_WILL_FREE)))
 		__iget(inode);
 	else
@@ -884,9 +918,11 @@
 		 * called yet, and somebody is calling igrab
 		 * while the inode is getting freed.
 		 */
-		inode = NULL;
+		ret = NULL;
+	spin_unlock(&inode->i_lock);
 	spin_unlock(&inode_lock);
-	return inode;
+
+	return ret;
 }
 EXPORT_SYMBOL(igrab);
 
@@ -919,6 +955,7 @@
 	inode = find_inode(sb, head, test, data);
 	if (inode) {
 		__iget(inode);
+		spin_unlock(&inode->i_lock);
 		spin_unlock(&inode_lock);
 		if (likely(wait))
 			wait_on_inode(inode);
@@ -952,6 +989,7 @@
 	inode = find_inode_fast(sb, head, ino);
 	if (inode) {
 		__iget(inode);
+		spin_unlock(&inode->i_lock);
 		spin_unlock(&inode_lock);
 		wait_on_inode(inode);
 		return inode;
@@ -1121,6 +1159,7 @@
 		struct inode *old = NULL;
 
 		spin_lock(&inode_lock);
+repeat:
 		spin_lock(&inode_hash_lock);
 		hlist_for_each_entry(old, node, head, i_hash) {
 			if (old->i_ino != ino)
@@ -1129,6 +1168,10 @@
 				continue;
 			if (old->i_state & (I_FREEING|I_WILL_FREE))
 				continue;
+			if (!spin_trylock(&old->i_lock)) {
+				spin_unlock(&inode_hash_lock);
+				goto repeat;
+			}
 			break;
 		}
 		if (likely(!node)) {
@@ -1139,6 +1182,7 @@
 		}
 		spin_unlock(&inode_hash_lock);
 		__iget(old);
+		spin_unlock(&old->i_lock);
 		spin_unlock(&inode_lock);
 		wait_on_inode(old);
 		if (unlikely(!hlist_unhashed(&old->i_hash))) {
@@ -1163,6 +1207,7 @@
 		struct inode *old = NULL;
 
 		spin_lock(&inode_lock);
+repeat:
 		spin_lock(&inode_hash_lock);
 		hlist_for_each_entry(old, node, head, i_hash) {
 			if (old->i_sb != sb)
@@ -1171,6 +1216,10 @@
 				continue;
 			if (old->i_state & (I_FREEING|I_WILL_FREE))
 				continue;
+			if (!spin_trylock(&old->i_lock)) {
+				spin_unlock(&inode_hash_lock);
+				goto repeat;
+			}
 			break;
 		}
 		if (likely(!node)) {
@@ -1181,6 +1230,7 @@
 		}
 		spin_unlock(&inode_hash_lock);
 		__iget(old);
+		spin_unlock(&old->i_lock);
 		spin_unlock(&inode_lock);
 		wait_on_inode(old);
 		if (unlikely(!hlist_unhashed(&old->i_hash))) {
@@ -1260,6 +1310,8 @@
 	const struct super_operations *op = inode->i_sb->s_op;
 	int drop;
 
+	spin_lock(&sb_inode_list_lock);
+	spin_lock(&inode->i_lock);
 	if (op && op->drop_inode)
 		drop = op->drop_inode(inode);
 	else
@@ -1270,14 +1322,20 @@
 			list_move(&inode->i_list, &inode_unused);
 		inodes_stat.nr_unused++;
 		if (sb->s_flags & MS_ACTIVE) {
+			spin_unlock(&inode->i_lock);
+			spin_unlock(&sb_inode_list_lock);
 			spin_unlock(&inode_lock);
 			return;
 		}
 		WARN_ON(inode->i_state & I_NEW);
 		inode->i_state |= I_WILL_FREE;
+		spin_unlock(&inode->i_lock);
+		spin_unlock(&sb_inode_list_lock);
 		spin_unlock(&inode_lock);
 		write_inode_now(inode, 1);
 		spin_lock(&inode_lock);
+		spin_lock(&sb_inode_list_lock);
+		spin_lock(&inode->i_lock);
 		WARN_ON(inode->i_state & I_NEW);
 		inode->i_state &= ~I_WILL_FREE;
 		inodes_stat.nr_unused--;
@@ -1286,12 +1344,12 @@
 		spin_unlock(&inode_hash_lock);
 	}
 	list_del_init(&inode->i_list);
-	spin_lock(&sb_inode_list_lock);
 	list_del_init(&inode->i_sb_list);
 	spin_unlock(&sb_inode_list_lock);
 	WARN_ON(inode->i_state & I_NEW);
 	inode->i_state |= I_FREEING;
 	inodes_stat.nr_inodes--;
+	spin_unlock(&inode->i_lock);
 	spin_unlock(&inode_lock);
 	evict(inode);
 	spin_lock(&inode_lock);
@@ -1500,6 +1558,8 @@
  * wake_up_inode() after removing from the hash list will DTRT.
  *
  * This is called with inode_lock held.
+ *
+ * Called with i_lock held and returns with it dropped.
  */
 static void __wait_on_freeing_inode(struct inode *inode)
 {
@@ -1507,6 +1567,7 @@
 	DEFINE_WAIT_BIT(wait, &inode->i_state, __I_NEW);
 	wq = bit_waitqueue(&inode->i_state, __I_NEW);
 	prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
+	spin_unlock(&inode->i_lock);
 	spin_unlock(&inode_lock);
 	schedule();
 	finish_wait(wq, &wait.wait);
Index: linux-2.6/fs/quota/dquot.c
===================================================================
--- linux-2.6.orig/fs/quota/dquot.c	2010-10-19 14:18:58.000000000 +1100
+++ linux-2.6/fs/quota/dquot.c	2010-10-19 14:19:32.000000000 +1100
@@ -246,6 +246,7 @@
 EXPORT_SYMBOL(dqstats);
 
 static qsize_t inode_get_rsv_space(struct inode *inode);
+static qsize_t __inode_get_rsv_space(struct inode *inode);
 static void __dquot_initialize(struct inode *inode, int type);
 
 static inline unsigned int
@@ -899,18 +900,26 @@
 	spin_lock(&inode_lock);
 	spin_lock(&sb_inode_list_lock);
 	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
-		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
+		spin_lock(&inode->i_lock);
+		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
+			spin_unlock(&inode->i_lock);
 			continue;
+		}
 #ifdef CONFIG_QUOTA_DEBUG
-		if (unlikely(inode_get_rsv_space(inode) > 0))
+		if (unlikely(__inode_get_rsv_space(inode) > 0))
 			reserved = 1;
 #endif
-		if (!atomic_read(&inode->i_writecount))
+		if (!atomic_read(&inode->i_writecount)) {
+			spin_unlock(&inode->i_lock);
 			continue;
-		if (!dqinit_needed(inode, type))
+		}
+		if (!dqinit_needed(inode, type)) {
+			spin_unlock(&inode->i_lock);
 			continue;
+		}
 
 		__iget(inode);
+		spin_unlock(&inode->i_lock);
 		spin_unlock(&sb_inode_list_lock);
 		spin_unlock(&inode_lock);
 
@@ -1494,6 +1503,17 @@
 }
 EXPORT_SYMBOL(inode_sub_rsv_space);
 
+/* no i_lock variant of inode_get_rsv_space */
+static qsize_t __inode_get_rsv_space(struct inode *inode)
+{
+	qsize_t ret;
+
+	if (!inode->i_sb->dq_op->get_reserved_space)
+		return 0;
+	ret = *inode_reserved_space(inode);
+	return ret;
+}
+
 static qsize_t inode_get_rsv_space(struct inode *inode)
 {
 	qsize_t ret;
Index: linux-2.6/fs/notify/inode_mark.c
===================================================================
--- linux-2.6.orig/fs/notify/inode_mark.c	2010-10-19 14:18:58.000000000 +1100
+++ linux-2.6/fs/notify/inode_mark.c	2010-10-19 14:19:37.000000000 +1100
@@ -243,13 +243,16 @@
 	list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
 		struct inode *need_iput_tmp;
 
+		spin_lock(&inode->i_lock);
 		/*
 		 * We cannot __iget() an inode in state I_FREEING,
 		 * I_WILL_FREE, or I_NEW which is fine because by that point
 		 * the inode cannot have any associated watches.
 		 */
-		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW))
+		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
+			spin_unlock(&inode->i_lock);
 			continue;
+		}
 
 		/*
 		 * If i_count is zero, the inode cannot have any watches and
@@ -257,8 +260,10 @@
 		 * evict all inodes with zero i_count from icache which is
 		 * unnecessarily violent and may in fact be illegal to do.
 		 */
-		if (!atomic_read(&inode->i_count))
+		if (!atomic_read(&inode->i_count)) {
+			spin_unlock(&inode->i_lock);
 			continue;
+		}
 
 		need_iput_tmp = need_iput;
 		need_iput = NULL;
@@ -268,13 +273,17 @@
 			__iget(inode);
 		else
 			need_iput_tmp = NULL;
+		spin_unlock(&inode->i_lock);
 
 		/* In case the dropping of a reference would nuke next_i. */
-		if ((&next_i->i_sb_list != list) &&
-		    atomic_read(&next_i->i_count) &&
-		    !(next_i->i_state & (I_FREEING | I_WILL_FREE))) {
-			__iget(next_i);
-			need_iput = next_i;
+		if (&next_i->i_sb_list != list) {
+			spin_lock(&next_i->i_lock);
+			if (atomic_read(&next_i->i_count) &&
+			    !(next_i->i_state & (I_FREEING | I_WILL_FREE))) {
+				__iget(next_i);
+				need_iput = next_i;
+			}
+			spin_unlock(&next_i->i_lock);
 		}
 
 		/*