From 365b94ae67d2915d412b593d47449a6bffed9d37 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 3 May 2012 14:47:55 +0200
Subject: writeback: Move clearing of I_SYNC into inode_sync_complete()

Move clearing of I_SYNC into inode_sync_complete().  It is more logical to have
clearing of I_SYNC bit and waking of waiters in one place. Also later we will
have two places needing to clear I_SYNC and wake up waiters so this allows them
to use the common helper. Moving of I_SYNC clearing to a later stage of
writeback_single_inode() is safe since we hold i_lock all the time.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
 fs/fs-writeback.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

(limited to 'fs')

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 539f36cf3e4a..dd41437b7a1f 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -231,11 +231,8 @@ static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
 
 static void inode_sync_complete(struct inode *inode)
 {
-	/*
-	 * Prevent speculative execution through
-	 * spin_unlock(&wb->list_lock);
-	 */
-
+	inode->i_state &= ~I_SYNC;
+	/* Waiters must see I_SYNC cleared before being woken up */
 	smp_mb();
 	wake_up_bit(&inode->i_state, __I_SYNC);
 }
@@ -436,7 +433,6 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 
 	spin_lock(&wb->list_lock);
 	spin_lock(&inode->i_lock);
-	inode->i_state &= ~I_SYNC;
 	if (!(inode->i_state & I_FREEING)) {
 		/*
 		 * Sync livelock prevention. Each inode is tagged and synced in
-- 
cgit v1.2.1


From cc1676d917f32504dbadc858fa790bc524c9f0da Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 3 May 2012 14:47:56 +0200
Subject: writeback: Move requeueing when I_SYNC set to writeback_sb_inodes()

When writeback_single_inode() is called on inode which has I_SYNC already
set while doing WB_SYNC_NONE, inode is moved to b_more_io list. However
this makes sense only if the caller is flusher thread. For other callers of
writeback_single_inode() it doesn't really make sense and may be even wrong
- flusher thread may be doing WB_SYNC_ALL writeback in parallel.

So we move requeueing from writeback_single_inode() to writeback_sb_inodes().

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
 fs/fs-writeback.c | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

(limited to 'fs')

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index dd41437b7a1f..65cd14769226 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -373,21 +373,8 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 		WARN_ON(inode->i_state & I_WILL_FREE);
 
 	if (inode->i_state & I_SYNC) {
-		/*
-		 * If this inode is locked for writeback and we are not doing
-		 * writeback-for-data-integrity, move it to b_more_io so that
-		 * writeback can proceed with the other inodes on s_io.
-		 *
-		 * We'll have another go at writing back this inode when we
-		 * completed a full scan of b_io.
-		 */
-		if (wbc->sync_mode != WB_SYNC_ALL) {
-			requeue_io(inode, wb);
-			trace_writeback_single_inode_requeue(inode, wbc,
-							     nr_to_write);
+		if (wbc->sync_mode != WB_SYNC_ALL)
 			return 0;
-		}
-
 		/*
 		 * It's a data-integrity sync.  We must wait.
 		 */
@@ -576,6 +563,21 @@ static long writeback_sb_inodes(struct super_block *sb,
 			redirty_tail(inode, wb);
 			continue;
 		}
+		if ((inode->i_state & I_SYNC) && wbc.sync_mode != WB_SYNC_ALL) {
+			/*
+			 * If this inode is locked for writeback and we are not
+			 * doing writeback-for-data-integrity, move it to
+			 * b_more_io so that writeback can proceed with the
+			 * other inodes on s_io.
+			 *
+			 * We'll have another go at writing back this inode
+			 * when we completed a full scan of b_io.
+			 */
+			spin_unlock(&inode->i_lock);
+			requeue_io(inode, wb);
+			trace_writeback_sb_inodes_requeue(inode);
+			continue;
+		}
 		__iget(inode);
 		write_chunk = writeback_chunk_size(wb->bdi, work);
 		wbc.nr_to_write = write_chunk;
-- 
cgit v1.2.1


From 6290be1c1dc6589eeda213aa40946b27fa4faac8 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 3 May 2012 14:47:57 +0200
Subject: writeback: Move I_DIRTY_PAGES handling

Instead of clearing I_DIRTY_PAGES and resetting it when we didn't succeed in
writing them all, just clear the bit only when we succeeded writing all the
pages. We also move the clearing of the bit close to other i_state handling to
separate it from writeback list handling. This is desirable because list
handling will differ for flusher thread and other writeback_single_inode()
callers in future. No filesystem plays any tricks with I_DIRTY_PAGES (like
checking it in ->writepages or ->write_inode implementation) so this movement
is safe.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
 fs/fs-writeback.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

(limited to 'fs')

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 65cd14769226..3804a10f2be7 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -385,7 +385,6 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 
 	/* 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(&wb->list_lock);
 
@@ -408,6 +407,9 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 	 * write_inode()
 	 */
 	spin_lock(&inode->i_lock);
+	/* Clear I_DIRTY_PAGES if we've written out all dirty pages */
+	if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
+		inode->i_state &= ~I_DIRTY_PAGES;
 	dirty = inode->i_state & I_DIRTY;
 	inode->i_state &= ~(I_DIRTY_SYNC | I_DIRTY_DATASYNC);
 	spin_unlock(&inode->i_lock);
@@ -435,7 +437,6 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 			 * We didn't write back all the pages.  nfs_writepages()
 			 * sometimes bales out without doing anything.
 			 */
-			inode->i_state |= I_DIRTY_PAGES;
 			if (wbc->nr_to_write <= 0) {
 				/*
 				 * slice used up: queue for next turn
-- 
cgit v1.2.1


From ccb26b5a65867839d95156e02ea4861f64a8cbf3 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 3 May 2012 14:47:58 +0200
Subject: writeback: Separate inode requeueing after writeback

Move inode requeueing after inode has been written out into a separate
function.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
 fs/fs-writeback.c | 102 +++++++++++++++++++++++++++++-------------------------
 1 file changed, 55 insertions(+), 47 deletions(-)

(limited to 'fs')

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 3804a10f2be7..5d3de002cb8e 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -344,6 +344,60 @@ static void inode_wait_for_writeback(struct inode *inode,
 	}
 }
 
+/*
+ * Find proper writeback list for the inode depending on its current state and
+ * possibly also change of its state while we were doing writeback.  Here we
+ * handle things such as livelock prevention or fairness of writeback among
+ * inodes. This function can be called only by flusher thread - noone else
+ * processes all inodes in writeback lists and requeueing inodes behind flusher
+ * thread's back can have unexpected consequences.
+ */
+static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
+			  struct writeback_control *wbc)
+{
+	if (inode->i_state & I_FREEING)
+		return;
+
+	/*
+	 * Sync livelock prevention. Each inode is tagged and synced in one
+	 * shot. If still dirty, it will be redirty_tail()'ed below.  Update
+	 * the dirty time to prevent enqueue and sync it again.
+	 */
+	if ((inode->i_state & I_DIRTY) &&
+	    (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
+		inode->dirtied_when = jiffies;
+
+	if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
+		/*
+		 * We didn't write back all the pages.  nfs_writepages()
+		 * sometimes bales out without doing anything.
+		 */
+		if (wbc->nr_to_write <= 0) {
+			/* Slice used up. Queue for next turn. */
+			requeue_io(inode, wb);
+		} else {
+			/*
+			 * Writeback blocked by something other than
+			 * congestion. Delay the inode for some time to
+			 * avoid spinning on the CPU (100% iowait)
+			 * retrying writeback of the dirty page/inode
+			 * that cannot be performed immediately.
+			 */
+			redirty_tail(inode, wb);
+		}
+	} else if (inode->i_state & I_DIRTY) {
+		/*
+		 * Filesystems can dirty the inode during writeback operations,
+		 * such as delayed allocation during submission or metadata
+		 * updates after data IO completion.
+		 */
+		redirty_tail(inode, wb);
+	} else {
+		/* The inode is clean. Remove from writeback lists. */
+		list_del_init(&inode->i_wb_list);
+	}
+}
+
 /*
  * Write out an inode's dirty pages.  Called under wb->list_lock and
  * inode->i_lock.  Either the caller has an active reference on the inode or
@@ -422,53 +476,7 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 
 	spin_lock(&wb->list_lock);
 	spin_lock(&inode->i_lock);
-	if (!(inode->i_state & I_FREEING)) {
-		/*
-		 * Sync livelock prevention. Each inode is tagged and synced in
-		 * one shot. If still dirty, it will be redirty_tail()'ed below.
-		 * Update the dirty time to prevent enqueue and sync it again.
-		 */
-		if ((inode->i_state & I_DIRTY) &&
-		    (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
-			inode->dirtied_when = jiffies;
-
-		if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
-			/*
-			 * We didn't write back all the pages.  nfs_writepages()
-			 * sometimes bales out without doing anything.
-			 */
-			if (wbc->nr_to_write <= 0) {
-				/*
-				 * slice used up: queue for next turn
-				 */
-				requeue_io(inode, wb);
-			} else {
-				/*
-				 * Writeback blocked by something other than
-				 * congestion. Delay the inode for some time to
-				 * avoid spinning on the CPU (100% iowait)
-				 * retrying writeback of the dirty page/inode
-				 * that cannot be performed immediately.
-				 */
-				redirty_tail(inode, wb);
-			}
-		} else if (inode->i_state & I_DIRTY) {
-			/*
-			 * Filesystems can dirty the inode during writeback
-			 * operations, such as delayed allocation during
-			 * submission or metadata updates after data IO
-			 * completion.
-			 */
-			redirty_tail(inode, wb);
-		} else {
-			/*
-			 * The inode is clean.  At this point we either have
-			 * a reference to the inode or it's on it's way out.
-			 * No need to add it back to the LRU.
-			 */
-			list_del_init(&inode->i_wb_list);
-		}
-	}
+	requeue_inode(inode, wb, wbc);
 	inode_sync_complete(inode);
 	trace_writeback_single_inode(inode, wbc, nr_to_write);
 	return ret;
-- 
cgit v1.2.1


From f0d07b7ffde758a27a48509ceda9a9ef413e0ea0 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 3 May 2012 14:47:59 +0200
Subject: writeback: Remove wb->list_lock from writeback_single_inode()

writeback_single_inode() doesn't need wb->list_lock for anything on entry now.
So remove the requirement. This makes locking of writeback_single_inode()
temporarily awkward (entering with i_lock, returning with i_lock and
wb->list_lock) but it will be sanitized in the next patch.

Also inode_wait_for_writeback() doesn't need wb->list_lock for anything. It was
just taking it to make usage convenient for callers but with
writeback_single_inode() changing it's not very convenient anymore. So remove
the lock from that function.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
 fs/fs-writeback.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

(limited to 'fs')

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5d3de002cb8e..3b87dc80fd30 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -328,8 +328,7 @@ static int write_inode(struct inode *inode, struct writeback_control *wbc)
 /*
  * Wait for writeback on an inode to complete.
  */
-static void inode_wait_for_writeback(struct inode *inode,
-				     struct bdi_writeback *wb)
+static void inode_wait_for_writeback(struct inode *inode)
 {
 	DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
 	wait_queue_head_t *wqh;
@@ -337,9 +336,7 @@ static void inode_wait_for_writeback(struct inode *inode,
 	wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
 	while (inode->i_state & I_SYNC) {
 		spin_unlock(&inode->i_lock);
-		spin_unlock(&wb->list_lock);
 		__wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
-		spin_lock(&wb->list_lock);
 		spin_lock(&inode->i_lock);
 	}
 }
@@ -418,7 +415,6 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 	unsigned dirty;
 	int ret;
 
-	assert_spin_locked(&wb->list_lock);
 	assert_spin_locked(&inode->i_lock);
 
 	if (!atomic_read(&inode->i_count))
@@ -432,7 +428,7 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 		/*
 		 * It's a data-integrity sync.  We must wait.
 		 */
-		inode_wait_for_writeback(inode, wb);
+		inode_wait_for_writeback(inode);
 	}
 
 	BUG_ON(inode->i_state & I_SYNC);
@@ -440,7 +436,6 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 	/* Set I_SYNC, reset I_DIRTY_PAGES */
 	inode->i_state |= I_SYNC;
 	spin_unlock(&inode->i_lock);
-	spin_unlock(&wb->list_lock);
 
 	ret = do_writepages(mapping, wbc);
 
@@ -587,6 +582,8 @@ static long writeback_sb_inodes(struct super_block *sb,
 			trace_writeback_sb_inodes_requeue(inode);
 			continue;
 		}
+		spin_unlock(&wb->list_lock);
+
 		__iget(inode);
 		write_chunk = writeback_chunk_size(wb->bdi, work);
 		wbc.nr_to_write = write_chunk;
@@ -803,8 +800,10 @@ static long wb_writeback(struct bdi_writeback *wb,
 			trace_writeback_wait(wb->bdi, work);
 			inode = wb_inode(wb->b_more_io.prev);
 			spin_lock(&inode->i_lock);
-			inode_wait_for_writeback(inode, wb);
+			spin_unlock(&wb->list_lock);
+			inode_wait_for_writeback(inode);
 			spin_unlock(&inode->i_lock);
+			spin_lock(&wb->list_lock);
 		}
 	}
 	spin_unlock(&wb->list_lock);
@@ -1350,7 +1349,6 @@ int write_inode_now(struct inode *inode, int sync)
 		wbc.nr_to_write = 0;
 
 	might_sleep();
-	spin_lock(&wb->list_lock);
 	spin_lock(&inode->i_lock);
 	ret = writeback_single_inode(inode, wb, &wbc);
 	spin_unlock(&inode->i_lock);
@@ -1375,7 +1373,6 @@ int sync_inode(struct inode *inode, struct writeback_control *wbc)
 	struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
 	int ret;
 
-	spin_lock(&wb->list_lock);
 	spin_lock(&inode->i_lock);
 	ret = writeback_single_inode(inode, wb, wbc);
 	spin_unlock(&inode->i_lock);
-- 
cgit v1.2.1


From 4f8ad655dbc82cf05d2edc11e66b78a42d38bf93 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 3 May 2012 14:48:00 +0200
Subject: writeback: Refactor writeback_single_inode()

The code in writeback_single_inode() is relatively complex. The list requeing
logic makes sense only for flusher thread but not really for sync_inode() or
write_inode_now() callers. Also when we want to get rid of inode references
held by flusher thread, we will need a special I_SYNC handling there.

So separate part of writeback_single_inode() which does the real writeback work
into __writeback_single_inode() and make writeback_single_inode() do only stuff
necessary for callers writing only one inode, moving the special list handling
into writeback_sb_inodes(). As a sideeffect this fixes a possible race where we
could skip some inode during sync(2) because other writer refiled it from b_io
to b_dirty list. Also I_SYNC handling is moved into the callers of
__writeback_single_inode() to make locking easier.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
 fs/fs-writeback.c | 142 +++++++++++++++++++++++++++++++++---------------------
 1 file changed, 86 insertions(+), 56 deletions(-)

(limited to 'fs')

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 3b87dc80fd30..5f2c68289610 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -364,6 +364,15 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
 	    (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages))
 		inode->dirtied_when = jiffies;
 
+	if (wbc->pages_skipped) {
+		/*
+		 * writeback is not making progress due to locked
+		 * buffers. Skip this inode for now.
+		 */
+		redirty_tail(inode, wb);
+		return;
+	}
+
 	if (mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
 		/*
 		 * We didn't write back all the pages.  nfs_writepages()
@@ -396,46 +405,20 @@ static void requeue_inode(struct inode *inode, struct bdi_writeback *wb,
 }
 
 /*
- * Write out an inode's dirty pages.  Called under wb->list_lock and
- * inode->i_lock.  Either the caller has an active reference on the inode or
- * the inode has I_WILL_FREE set.
- *
- * If `wait' is set, wait on the writeout.
- *
- * The whole writeout design is quite complex and fragile.  We want to avoid
- * starvation of particular inodes when others are being redirtied, prevent
- * livelocks, etc.
+ * Write out an inode and its dirty pages. Do not update the writeback list
+ * linkage. That is left to the caller. The caller is also responsible for
+ * setting I_SYNC flag and calling inode_sync_complete() to clear it.
  */
 static int
-writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
-		       struct writeback_control *wbc)
+__writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
+			 struct writeback_control *wbc)
 {
 	struct address_space *mapping = inode->i_mapping;
 	long nr_to_write = wbc->nr_to_write;
 	unsigned dirty;
 	int ret;
 
-	assert_spin_locked(&inode->i_lock);
-
-	if (!atomic_read(&inode->i_count))
-		WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
-	else
-		WARN_ON(inode->i_state & I_WILL_FREE);
-
-	if (inode->i_state & I_SYNC) {
-		if (wbc->sync_mode != WB_SYNC_ALL)
-			return 0;
-		/*
-		 * It's a data-integrity sync.  We must wait.
-		 */
-		inode_wait_for_writeback(inode);
-	}
-
-	BUG_ON(inode->i_state & I_SYNC);
-
-	/* Set I_SYNC, reset I_DIRTY_PAGES */
-	inode->i_state |= I_SYNC;
-	spin_unlock(&inode->i_lock);
+	WARN_ON(!(inode->i_state & I_SYNC));
 
 	ret = do_writepages(mapping, wbc);
 
@@ -468,12 +451,65 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 		if (ret == 0)
 			ret = err;
 	}
+	trace_writeback_single_inode(inode, wbc, nr_to_write);
+	return ret;
+}
+
+/*
+ * Write out an inode's dirty pages. Either the caller has an active reference
+ * on the inode or the inode has I_WILL_FREE set.
+ *
+ * This function is designed to be called for writing back one inode which
+ * we go e.g. from filesystem. Flusher thread uses __writeback_single_inode()
+ * and does more profound writeback list handling in writeback_sb_inodes().
+ */
+static int
+writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
+		       struct writeback_control *wbc)
+{
+	int ret = 0;
+
+	spin_lock(&inode->i_lock);
+	if (!atomic_read(&inode->i_count))
+		WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
+	else
+		WARN_ON(inode->i_state & I_WILL_FREE);
+
+	if (inode->i_state & I_SYNC) {
+		if (wbc->sync_mode != WB_SYNC_ALL)
+			goto out;
+		/*
+		 * It's a data-integrity sync.  We must wait.
+		 */
+		inode_wait_for_writeback(inode);
+	}
+	WARN_ON(inode->i_state & I_SYNC);
+	/*
+	 * Skip inode if it is clean. We don't want to mess with writeback
+	 * lists in this function since flusher thread may be doing for example
+	 * sync in parallel and if we move the inode, it could get skipped. So
+	 * here we make sure inode is on some writeback list and leave it there
+	 * unless we have completely cleaned the inode.
+	 */
+	if (!(inode->i_state & I_DIRTY))
+		goto out;
+	inode->i_state |= I_SYNC;
+	spin_unlock(&inode->i_lock);
+
+	ret = __writeback_single_inode(inode, wb, wbc);
 
 	spin_lock(&wb->list_lock);
 	spin_lock(&inode->i_lock);
-	requeue_inode(inode, wb, wbc);
+	/*
+	 * If inode is clean, remove it from writeback lists. Otherwise don't
+	 * touch it. See comment above for explanation.
+	 */
+	if (!(inode->i_state & I_DIRTY))
+		list_del_init(&inode->i_wb_list);
+	spin_unlock(&wb->list_lock);
 	inode_sync_complete(inode);
-	trace_writeback_single_inode(inode, wbc, nr_to_write);
+out:
+	spin_unlock(&inode->i_lock);
 	return ret;
 }
 
@@ -585,23 +621,29 @@ static long writeback_sb_inodes(struct super_block *sb,
 		spin_unlock(&wb->list_lock);
 
 		__iget(inode);
+		/*
+		 * We already requeued the inode if it had I_SYNC set and we
+		 * are doing WB_SYNC_NONE writeback. So this catches only the
+		 * WB_SYNC_ALL case.
+		 */
+		if (inode->i_state & I_SYNC)
+			inode_wait_for_writeback(inode);
+		inode->i_state |= I_SYNC;
+		spin_unlock(&inode->i_lock);
 		write_chunk = writeback_chunk_size(wb->bdi, work);
 		wbc.nr_to_write = write_chunk;
 		wbc.pages_skipped = 0;
 
-		writeback_single_inode(inode, wb, &wbc);
+		__writeback_single_inode(inode, wb, &wbc);
 
 		work->nr_pages -= write_chunk - wbc.nr_to_write;
 		wrote += write_chunk - wbc.nr_to_write;
+		spin_lock(&wb->list_lock);
+		spin_lock(&inode->i_lock);
 		if (!(inode->i_state & I_DIRTY))
 			wrote++;
-		if (wbc.pages_skipped) {
-			/*
-			 * writeback is not making progress due to locked
-			 * buffers.  Skip this inode for now.
-			 */
-			redirty_tail(inode, wb);
-		}
+		requeue_inode(inode, wb, &wbc);
+		inode_sync_complete(inode);
 		spin_unlock(&inode->i_lock);
 		spin_unlock(&wb->list_lock);
 		iput(inode);
@@ -1337,7 +1379,6 @@ EXPORT_SYMBOL(sync_inodes_sb);
 int write_inode_now(struct inode *inode, int sync)
 {
 	struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
-	int ret;
 	struct writeback_control wbc = {
 		.nr_to_write = LONG_MAX,
 		.sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
@@ -1349,11 +1390,7 @@ int write_inode_now(struct inode *inode, int sync)
 		wbc.nr_to_write = 0;
 
 	might_sleep();
-	spin_lock(&inode->i_lock);
-	ret = writeback_single_inode(inode, wb, &wbc);
-	spin_unlock(&inode->i_lock);
-	spin_unlock(&wb->list_lock);
-	return ret;
+	return writeback_single_inode(inode, wb, &wbc);
 }
 EXPORT_SYMBOL(write_inode_now);
 
@@ -1370,14 +1407,7 @@ EXPORT_SYMBOL(write_inode_now);
  */
 int sync_inode(struct inode *inode, struct writeback_control *wbc)
 {
-	struct bdi_writeback *wb = &inode_to_bdi(inode)->wb;
-	int ret;
-
-	spin_lock(&inode->i_lock);
-	ret = writeback_single_inode(inode, wb, wbc);
-	spin_unlock(&inode->i_lock);
-	spin_unlock(&wb->list_lock);
-	return ret;
+	return writeback_single_inode(inode, &inode_to_bdi(inode)->wb, wbc);
 }
 EXPORT_SYMBOL(sync_inode);
 
-- 
cgit v1.2.1


From 7994e6f7254354e03028a11f98a27bd67dace9f1 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 3 May 2012 14:48:01 +0200
Subject: vfs: Move waiting for inode writeback from end_writeback() to
 evict_inode()

Currently, I_SYNC can never be set when evict_inode() (and thus
end_writeback()) is called because flusher thread holds inode reference while
inode is under writeback. As a result inode_sync_wait() in those places
currently does nothing. However that is going to change and unveils problems
with calling inode_sync_wait() from end_writeback(). Several filesystems call
end_writeback() after they have deleted the inode (btrfs, gfs2, ...) and other
filesystems (ext3, ext4, reiserfs, ...) can deadlock when waiting for I_SYNC
because they call end_writeback() from within a transaction.

To avoid these issues, we move inode_sync_wait() into evict_inode() before
calling ->evict_inode(). That way we preserve the current property that
->evict_inode() and writeback never run in parallel and all filesystems are
safe.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
 fs/inode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'fs')

diff --git a/fs/inode.c b/fs/inode.c
index 9f4f5fecc096..501fc5daf6f4 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -500,7 +500,6 @@ void end_writeback(struct inode *inode)
 	BUG_ON(!list_empty(&inode->i_data.private_list));
 	BUG_ON(!(inode->i_state & I_FREEING));
 	BUG_ON(inode->i_state & I_CLEAR);
-	inode_sync_wait(inode);
 	/* don't need i_lock here, no concurrent mods to i_state */
 	inode->i_state = I_FREEING | I_CLEAR;
 }
@@ -531,6 +530,8 @@ static void evict(struct inode *inode)
 
 	inode_sb_list_del(inode);
 
+	inode_sync_wait(inode);
+
 	if (op->evict_inode) {
 		op->evict_inode(inode);
 	} else {
-- 
cgit v1.2.1


From dbd5768f87ff6fb0a4fe09c4d7b6c4a24de99430 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 3 May 2012 14:48:02 +0200
Subject: vfs: Rename end_writeback() to clear_inode()

After we moved inode_sync_wait() from end_writeback() it doesn't make sense
to call the function end_writeback() anymore. Rename it to clear_inode()
which well says what the function really does - set I_CLEAR flag.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
 fs/9p/vfs_inode.c        | 2 +-
 fs/affs/inode.c          | 2 +-
 fs/afs/inode.c           | 2 +-
 fs/autofs4/inode.c       | 2 +-
 fs/bfs/inode.c           | 2 +-
 fs/binfmt_misc.c         | 2 +-
 fs/block_dev.c           | 2 +-
 fs/btrfs/inode.c         | 2 +-
 fs/cifs/cifsfs.c         | 2 +-
 fs/coda/inode.c          | 2 +-
 fs/ecryptfs/super.c      | 2 +-
 fs/exofs/inode.c         | 4 ++--
 fs/ext2/inode.c          | 2 +-
 fs/ext3/inode.c          | 6 +++---
 fs/ext4/super.c          | 2 +-
 fs/fat/inode.c           | 2 +-
 fs/freevxfs/vxfs_inode.c | 2 +-
 fs/fuse/inode.c          | 2 +-
 fs/gfs2/super.c          | 2 +-
 fs/hfs/inode.c           | 2 +-
 fs/hfsplus/super.c       | 2 +-
 fs/hostfs/hostfs_kern.c  | 2 +-
 fs/hpfs/inode.c          | 2 +-
 fs/hppfs/hppfs.c         | 2 +-
 fs/hugetlbfs/inode.c     | 2 +-
 fs/inode.c               | 6 +++---
 fs/jffs2/fs.c            | 2 +-
 fs/jfs/inode.c           | 2 +-
 fs/logfs/readwrite.c     | 2 +-
 fs/minix/inode.c         | 2 +-
 fs/ncpfs/inode.c         | 2 +-
 fs/nfs/inode.c           | 4 ++--
 fs/nilfs2/inode.c        | 4 ++--
 fs/ntfs/inode.c          | 2 +-
 fs/ocfs2/dlmfs/dlmfs.c   | 2 +-
 fs/ocfs2/inode.c         | 2 +-
 fs/omfs/inode.c          | 2 +-
 fs/proc/inode.c          | 2 +-
 fs/pstore/inode.c        | 2 +-
 fs/reiserfs/inode.c      | 4 ++--
 fs/sysfs/inode.c         | 2 +-
 fs/sysv/inode.c          | 2 +-
 fs/ubifs/super.c         | 2 +-
 fs/udf/inode.c           | 2 +-
 fs/ufs/inode.c           | 2 +-
 fs/xfs/xfs_super.c       | 2 +-
 46 files changed, 54 insertions(+), 54 deletions(-)

(limited to 'fs')

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 014c8dd62962..57ccb7537dae 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -448,7 +448,7 @@ void v9fs_evict_inode(struct inode *inode)
 	struct v9fs_inode *v9inode = V9FS_I(inode);
 
 	truncate_inode_pages(inode->i_mapping, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	filemap_fdatawrite(inode->i_mapping);
 
 #ifdef CONFIG_9P_FSCACHE
diff --git a/fs/affs/inode.c b/fs/affs/inode.c
index 88a4b0b50058..8bc4a59f4e7e 100644
--- a/fs/affs/inode.c
+++ b/fs/affs/inode.c
@@ -264,7 +264,7 @@ affs_evict_inode(struct inode *inode)
 	}
 
 	invalidate_inode_buffers(inode);
-	end_writeback(inode);
+	clear_inode(inode);
 	affs_free_prealloc(inode);
 	cache_page = (unsigned long)AFFS_I(inode)->i_lc;
 	if (cache_page) {
diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index d890ae3b2ce6..95cffd38239f 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -423,7 +423,7 @@ void afs_evict_inode(struct inode *inode)
 	ASSERTCMP(inode->i_ino, ==, vnode->fid.vnode);
 
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 
 	afs_give_up_callback(vnode);
 
diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
index d8dc002e9cc3..df31ddb58228 100644
--- a/fs/autofs4/inode.c
+++ b/fs/autofs4/inode.c
@@ -101,7 +101,7 @@ static int autofs4_show_options(struct seq_file *m, struct dentry *root)
 
 static void autofs4_evict_inode(struct inode *inode)
 {
-	end_writeback(inode);
+	clear_inode(inode);
 	kfree(inode->i_private);
 }
 
diff --git a/fs/bfs/inode.c b/fs/bfs/inode.c
index e23dc7c8b884..9870417c26e7 100644
--- a/fs/bfs/inode.c
+++ b/fs/bfs/inode.c
@@ -174,7 +174,7 @@ static void bfs_evict_inode(struct inode *inode)
 
 	truncate_inode_pages(&inode->i_data, 0);
 	invalidate_inode_buffers(inode);
-	end_writeback(inode);
+	clear_inode(inode);
 
 	if (inode->i_nlink)
 		return;
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 613aa0618235..790b3cddca67 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -505,7 +505,7 @@ static struct inode *bm_get_inode(struct super_block *sb, int mode)
 
 static void bm_evict_inode(struct inode *inode)
 {
-	end_writeback(inode);
+	clear_inode(inode);
 	kfree(inode->i_private);
 }
 
diff --git a/fs/block_dev.c b/fs/block_dev.c
index e08f6a20a5bb..d8a7959a9654 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -487,7 +487,7 @@ static void bdev_evict_inode(struct inode *inode)
 	struct list_head *p;
 	truncate_inode_pages(&inode->i_data, 0);
 	invalidate_inode_buffers(inode); /* is it needed here? */
-	end_writeback(inode);
+	clear_inode(inode);
 	spin_lock(&bdev_lock);
 	while ( (p = bdev->bd_inodes.next) != &bdev->bd_inodes ) {
 		__bd_forget(list_entry(p, struct inode, i_devices));
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 115bc05e42b0..5c058c4d3283 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3756,7 +3756,7 @@ void btrfs_evict_inode(struct inode *inode)
 	btrfs_end_transaction(trans, root);
 	btrfs_btree_balance_dirty(root, nr);
 no_delete:
-	end_writeback(inode);
+	clear_inode(inode);
 	return;
 }
 
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index d34212822444..acb138f0eba0 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -272,7 +272,7 @@ static void
 cifs_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	cifs_fscache_release_inode_cookie(inode);
 }
 
diff --git a/fs/coda/inode.c b/fs/coda/inode.c
index 2870597b5c9d..f1813120d753 100644
--- a/fs/coda/inode.c
+++ b/fs/coda/inode.c
@@ -244,7 +244,7 @@ static void coda_put_super(struct super_block *sb)
 static void coda_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	coda_cache_clear_inode(inode);
 }
 
diff --git a/fs/ecryptfs/super.c b/fs/ecryptfs/super.c
index 2dd946b636d2..e879cf8ff0b1 100644
--- a/fs/ecryptfs/super.c
+++ b/fs/ecryptfs/super.c
@@ -133,7 +133,7 @@ static int ecryptfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 static void ecryptfs_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	iput(ecryptfs_inode_to_lower(inode));
 }
 
diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c
index ea5e1f97806a..5badb0c039de 100644
--- a/fs/exofs/inode.c
+++ b/fs/exofs/inode.c
@@ -1473,7 +1473,7 @@ void exofs_evict_inode(struct inode *inode)
 		goto no_delete;
 
 	inode->i_size = 0;
-	end_writeback(inode);
+	clear_inode(inode);
 
 	/* if we are deleting an obj that hasn't been created yet, wait.
 	 * This also makes sure that create_done cannot be called with an
@@ -1503,5 +1503,5 @@ void exofs_evict_inode(struct inode *inode)
 	return;
 
 no_delete:
-	end_writeback(inode);
+	clear_inode(inode);
 }
diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 740cad8dcd8d..37b8bf606f45 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -90,7 +90,7 @@ void ext2_evict_inode(struct inode * inode)
 	}
 
 	invalidate_inode_buffers(inode);
-	end_writeback(inode);
+	clear_inode(inode);
 
 	ext2_discard_reservation(inode);
 	rsv = EXT2_I(inode)->i_block_alloc_info;
diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 10d7812f6021..ca5eb6189ee9 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -272,18 +272,18 @@ void ext3_evict_inode (struct inode *inode)
 	if (ext3_mark_inode_dirty(handle, inode)) {
 		/* If that failed, just dquot_drop() and be done with that */
 		dquot_drop(inode);
-		end_writeback(inode);
+		clear_inode(inode);
 	} else {
 		ext3_xattr_delete_inode(handle, inode);
 		dquot_free_inode(inode);
 		dquot_drop(inode);
-		end_writeback(inode);
+		clear_inode(inode);
 		ext3_free_inode(handle, inode);
 	}
 	ext3_journal_stop(handle);
 	return;
 no_delete:
-	end_writeback(inode);
+	clear_inode(inode);
 	dquot_drop(inode);
 }
 
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ceebaf853beb..2484f560483a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1007,7 +1007,7 @@ static void destroy_inodecache(void)
 void ext4_clear_inode(struct inode *inode)
 {
 	invalidate_inode_buffers(inode);
-	end_writeback(inode);
+	clear_inode(inode);
 	dquot_drop(inode);
 	ext4_discard_preallocations(inode);
 	if (EXT4_I(inode)->jinode) {
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 21687e31acc0..b3d290c1b513 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -454,7 +454,7 @@ static void fat_evict_inode(struct inode *inode)
 		fat_truncate_blocks(inode, 0);
 	}
 	invalidate_inode_buffers(inode);
-	end_writeback(inode);
+	clear_inode(inode);
 	fat_cache_inval_inode(inode);
 	fat_detach(inode);
 }
diff --git a/fs/freevxfs/vxfs_inode.c b/fs/freevxfs/vxfs_inode.c
index cf9ef918a2a9..ef67c95f12d4 100644
--- a/fs/freevxfs/vxfs_inode.c
+++ b/fs/freevxfs/vxfs_inode.c
@@ -355,6 +355,6 @@ void
 vxfs_evict_inode(struct inode *ip)
 {
 	truncate_inode_pages(&ip->i_data, 0);
-	end_writeback(ip);
+	clear_inode(ip);
 	call_rcu(&ip->i_rcu, vxfs_i_callback);
 }
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 4aec5995867e..87e61152b34e 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -122,7 +122,7 @@ static void fuse_destroy_inode(struct inode *inode)
 static void fuse_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	if (inode->i_sb->s_flags & MS_ACTIVE) {
 		struct fuse_conn *fc = get_fuse_conn(inode);
 		struct fuse_inode *fi = get_fuse_inode(inode);
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 6172fa77ad59..713e621c240b 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -1554,7 +1554,7 @@ out_unlock:
 out:
 	/* Case 3 starts here */
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	gfs2_dir_hash_inval(ip);
 	ip->i_gl->gl_object = NULL;
 	flush_delayed_work_sync(&ip->i_gl->gl_work);
diff --git a/fs/hfs/inode.c b/fs/hfs/inode.c
index 737dbeb64320..761ec06354b4 100644
--- a/fs/hfs/inode.c
+++ b/fs/hfs/inode.c
@@ -532,7 +532,7 @@ out:
 void hfs_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	if (HFS_IS_RSRC(inode) && HFS_I(inode)->rsrc_inode) {
 		HFS_I(HFS_I(inode)->rsrc_inode)->rsrc_inode = NULL;
 		iput(HFS_I(inode)->rsrc_inode);
diff --git a/fs/hfsplus/super.c b/fs/hfsplus/super.c
index ceb1c281eefb..a9bca4b8768b 100644
--- a/fs/hfsplus/super.c
+++ b/fs/hfsplus/super.c
@@ -154,7 +154,7 @@ static void hfsplus_evict_inode(struct inode *inode)
 {
 	dprint(DBG_INODE, "hfsplus_evict_inode: %lu\n", inode->i_ino);
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	if (HFSPLUS_IS_RSRC(inode)) {
 		HFSPLUS_I(HFSPLUS_I(inode)->rsrc_inode)->rsrc_inode = NULL;
 		iput(HFSPLUS_I(inode)->rsrc_inode);
diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
index 07c516bfea76..2afa5bbccf9b 100644
--- a/fs/hostfs/hostfs_kern.c
+++ b/fs/hostfs/hostfs_kern.c
@@ -240,7 +240,7 @@ static struct inode *hostfs_alloc_inode(struct super_block *sb)
 static void hostfs_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	if (HOSTFS_I(inode)->fd != -1) {
 		close_file(&HOSTFS_I(inode)->fd);
 		HOSTFS_I(inode)->fd = -1;
diff --git a/fs/hpfs/inode.c b/fs/hpfs/inode.c
index 3b2cec29972b..b43066cbdc6a 100644
--- a/fs/hpfs/inode.c
+++ b/fs/hpfs/inode.c
@@ -299,7 +299,7 @@ void hpfs_write_if_changed(struct inode *inode)
 void hpfs_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	if (!inode->i_nlink) {
 		hpfs_lock(inode->i_sb);
 		hpfs_remove_fnode(inode->i_sb, inode->i_ino);
diff --git a/fs/hppfs/hppfs.c b/fs/hppfs/hppfs.c
index a80e45a690ac..d4f93b52cec5 100644
--- a/fs/hppfs/hppfs.c
+++ b/fs/hppfs/hppfs.c
@@ -614,7 +614,7 @@ static struct inode *hppfs_alloc_inode(struct super_block *sb)
 
 void hppfs_evict_inode(struct inode *ino)
 {
-	end_writeback(ino);
+	clear_inode(ino);
 	dput(HPPFS_I(ino)->proc_dentry);
 	mntput(ino->i_sb->s_fs_info);
 }
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 28cf06e4ec84..568193d5153c 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -393,7 +393,7 @@ static void truncate_hugepages(struct inode *inode, loff_t lstart)
 static void hugetlbfs_evict_inode(struct inode *inode)
 {
 	truncate_hugepages(inode, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 }
 
 static inline void
diff --git a/fs/inode.c b/fs/inode.c
index 501fc5daf6f4..02c0fa5e16a4 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -486,7 +486,7 @@ void __remove_inode_hash(struct inode *inode)
 }
 EXPORT_SYMBOL(__remove_inode_hash);
 
-void end_writeback(struct inode *inode)
+void clear_inode(struct inode *inode)
 {
 	might_sleep();
 	/*
@@ -503,7 +503,7 @@ void end_writeback(struct inode *inode)
 	/* don't need i_lock here, no concurrent mods to i_state */
 	inode->i_state = I_FREEING | I_CLEAR;
 }
-EXPORT_SYMBOL(end_writeback);
+EXPORT_SYMBOL(clear_inode);
 
 /*
  * Free the inode passed in, removing it from the lists it is still connected
@@ -537,7 +537,7 @@ static void evict(struct inode *inode)
 	} else {
 		if (inode->i_data.nrpages)
 			truncate_inode_pages(&inode->i_data, 0);
-		end_writeback(inode);
+		clear_inode(inode);
 	}
 	if (S_ISBLK(inode->i_mode) && inode->i_bdev)
 		bd_forget(inode);
diff --git a/fs/jffs2/fs.c b/fs/jffs2/fs.c
index bb6f993ebca9..3d3092eda811 100644
--- a/fs/jffs2/fs.c
+++ b/fs/jffs2/fs.c
@@ -240,7 +240,7 @@ void jffs2_evict_inode (struct inode *inode)
 	jffs2_dbg(1, "%s(): ino #%lu mode %o\n",
 		  __func__, inode->i_ino, inode->i_mode);
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	jffs2_do_clear_inode(c, f);
 }
 
diff --git a/fs/jfs/inode.c b/fs/jfs/inode.c
index 77b69b27f825..4692bf3ca8cb 100644
--- a/fs/jfs/inode.c
+++ b/fs/jfs/inode.c
@@ -169,7 +169,7 @@ void jfs_evict_inode(struct inode *inode)
 	} else {
 		truncate_inode_pages(&inode->i_data, 0);
 	}
-	end_writeback(inode);
+	clear_inode(inode);
 	dquot_drop(inode);
 }
 
diff --git a/fs/logfs/readwrite.c b/fs/logfs/readwrite.c
index e3ab5e5a904c..f1cb512c5019 100644
--- a/fs/logfs/readwrite.c
+++ b/fs/logfs/readwrite.c
@@ -2175,7 +2175,7 @@ void logfs_evict_inode(struct inode *inode)
 		}
 	}
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 
 	/* Cheaper version of write_inode.  All changes are concealed in
 	 * aliases, which are moved back.  No write to the medium happens.
diff --git a/fs/minix/inode.c b/fs/minix/inode.c
index fcb05d2c6b5f..2a503ad020d5 100644
--- a/fs/minix/inode.c
+++ b/fs/minix/inode.c
@@ -32,7 +32,7 @@ static void minix_evict_inode(struct inode *inode)
 		minix_truncate(inode);
 	}
 	invalidate_inode_buffers(inode);
-	end_writeback(inode);
+	clear_inode(inode);
 	if (!inode->i_nlink)
 		minix_free_inode(inode);
 }
diff --git a/fs/ncpfs/inode.c b/fs/ncpfs/inode.c
index 87484fb8d177..333df07ae3bd 100644
--- a/fs/ncpfs/inode.c
+++ b/fs/ncpfs/inode.c
@@ -292,7 +292,7 @@ static void
 ncp_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 
 	if (S_ISDIR(inode->i_mode)) {
 		DDPRINTK("ncp_evict_inode: put directory %ld\n", inode->i_ino);
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index e8bbfa5b3500..c6073139b402 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -121,7 +121,7 @@ static void nfs_clear_inode(struct inode *inode)
 void nfs_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	nfs_clear_inode(inode);
 }
 
@@ -1500,7 +1500,7 @@ static int nfs_update_inode(struct inode *inode, struct nfs_fattr *fattr)
 void nfs4_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	pnfs_return_layout(inode);
 	pnfs_destroy_layout(NFS_I(inode));
 	/* If we are holding a delegation, return it! */
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 8f7b95ac1f7e..7cc64465ec26 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -734,7 +734,7 @@ void nilfs_evict_inode(struct inode *inode)
 	if (inode->i_nlink || !ii->i_root || unlikely(is_bad_inode(inode))) {
 		if (inode->i_data.nrpages)
 			truncate_inode_pages(&inode->i_data, 0);
-		end_writeback(inode);
+		clear_inode(inode);
 		nilfs_clear_inode(inode);
 		return;
 	}
@@ -746,7 +746,7 @@ void nilfs_evict_inode(struct inode *inode)
 	/* TODO: some of the following operations may fail.  */
 	nilfs_truncate_bmap(ii, 0);
 	nilfs_mark_inode_dirty(inode);
-	end_writeback(inode);
+	clear_inode(inode);
 
 	ret = nilfs_ifile_delete_inode(ii->i_root->ifile, inode->i_ino);
 	if (!ret)
diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c
index 2eaa66652944..c6dbd3db6ca8 100644
--- a/fs/ntfs/inode.c
+++ b/fs/ntfs/inode.c
@@ -2258,7 +2258,7 @@ void ntfs_evict_big_inode(struct inode *vi)
 	ntfs_inode *ni = NTFS_I(vi);
 
 	truncate_inode_pages(&vi->i_data, 0);
-	end_writeback(vi);
+	clear_inode(vi);
 
 #ifdef NTFS_RW
 	if (NInoDirty(ni)) {
diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
index 3b5825ef3193..e31d6ae013ab 100644
--- a/fs/ocfs2/dlmfs/dlmfs.c
+++ b/fs/ocfs2/dlmfs/dlmfs.c
@@ -367,7 +367,7 @@ static void dlmfs_evict_inode(struct inode *inode)
 	int status;
 	struct dlmfs_inode_private *ip;
 
-	end_writeback(inode);
+	clear_inode(inode);
 
 	mlog(0, "inode %lu\n", inode->i_ino);
 
diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index 17454a904d7b..735514ca400f 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -1069,7 +1069,7 @@ static void ocfs2_clear_inode(struct inode *inode)
 	int status;
 	struct ocfs2_inode_info *oi = OCFS2_I(inode);
 
-	end_writeback(inode);
+	clear_inode(inode);
 	trace_ocfs2_clear_inode((unsigned long long)oi->ip_blkno,
 				inode->i_nlink);
 
diff --git a/fs/omfs/inode.c b/fs/omfs/inode.c
index dbc842222589..e6213b3725d1 100644
--- a/fs/omfs/inode.c
+++ b/fs/omfs/inode.c
@@ -184,7 +184,7 @@ int omfs_sync_inode(struct inode *inode)
 static void omfs_evict_inode(struct inode *inode)
 {
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 
 	if (inode->i_nlink)
 		return;
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 205c92280838..29ab406b3704 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -33,7 +33,7 @@ static void proc_evict_inode(struct inode *inode)
 	const struct proc_ns_operations *ns_ops;
 
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 
 	/* Stop tracking associated processes */
 	put_pid(PROC_I(inode)->pid);
diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 19507889bb7f..aeb19e68e086 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -85,7 +85,7 @@ static void pstore_evict_inode(struct inode *inode)
 	struct pstore_private	*p = inode->i_private;
 	unsigned long		flags;
 
-	end_writeback(inode);
+	clear_inode(inode);
 	if (p) {
 		spin_lock_irqsave(&allpstore_lock, flags);
 		list_del(&p->list);
diff --git a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c
index 494c315c7417..59d06871a850 100644
--- a/fs/reiserfs/inode.c
+++ b/fs/reiserfs/inode.c
@@ -76,14 +76,14 @@ void reiserfs_evict_inode(struct inode *inode)
 		;
 	}
       out:
-	end_writeback(inode);	/* note this must go after the journal_end to prevent deadlock */
+	clear_inode(inode);	/* note this must go after the journal_end to prevent deadlock */
 	dquot_drop(inode);
 	inode->i_blocks = 0;
 	reiserfs_write_unlock_once(inode->i_sb, depth);
 	return;
 
 no_delete:
-	end_writeback(inode);
+	clear_inode(inode);
 	dquot_drop(inode);
 }
 
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index feb2d69396cf..b8ce6a98933f 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -310,7 +310,7 @@ void sysfs_evict_inode(struct inode *inode)
 	struct sysfs_dirent *sd  = inode->i_private;
 
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	sysfs_put(sd);
 }
 
diff --git a/fs/sysv/inode.c b/fs/sysv/inode.c
index 3da5ce25faf0..08d0b2568cd3 100644
--- a/fs/sysv/inode.c
+++ b/fs/sysv/inode.c
@@ -316,7 +316,7 @@ static void sysv_evict_inode(struct inode *inode)
 		sysv_truncate(inode);
 	}
 	invalidate_inode_buffers(inode);
-	end_writeback(inode);
+	clear_inode(inode);
 	if (!inode->i_nlink)
 		sysv_free_inode(inode);
 }
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 76e4e0566ad6..7bf60ae58ed4 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -378,7 +378,7 @@ out:
 		smp_wmb();
 	}
 done:
-	end_writeback(inode);
+	clear_inode(inode);
 }
 
 static void ubifs_dirty_inode(struct inode *inode, int flags)
diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 7d7528008359..873e1bab9c4c 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -80,7 +80,7 @@ void udf_evict_inode(struct inode *inode)
 	} else
 		truncate_inode_pages(&inode->i_data, 0);
 	invalidate_inode_buffers(inode);
-	end_writeback(inode);
+	clear_inode(inode);
 	if (iinfo->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB &&
 	    inode->i_size != iinfo->i_lenExtents) {
 		udf_warn(inode->i_sb, "Inode %lu (mode %o) has inode size %llu different from extent length %llu. Filesystem need not be standards compliant.\n",
diff --git a/fs/ufs/inode.c b/fs/ufs/inode.c
index 7cdd3953d67e..dd7c89d8a1c1 100644
--- a/fs/ufs/inode.c
+++ b/fs/ufs/inode.c
@@ -895,7 +895,7 @@ void ufs_evict_inode(struct inode * inode)
 	}
 
 	invalidate_inode_buffers(inode);
-	end_writeback(inode);
+	clear_inode(inode);
 
 	if (want_delete) {
 		lock_ufs(inode->i_sb);
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index dab9a5f6dfd6..5b806f23ad0a 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -926,7 +926,7 @@ xfs_fs_evict_inode(
 	trace_xfs_evict_inode(ip);
 
 	truncate_inode_pages(&inode->i_data, 0);
-	end_writeback(inode);
+	clear_inode(inode);
 	XFS_STATS_INC(vn_rele);
 	XFS_STATS_INC(vn_remove);
 	XFS_STATS_DEC(vn_active);
-- 
cgit v1.2.1


From 169ebd90131b2ffca74bb2dbe7eeacd39fb83714 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 3 May 2012 14:48:03 +0200
Subject: writeback: Avoid iput() from flusher thread

Doing iput() from flusher thread (writeback_sb_inodes()) can create problems
because iput() can do a lot of work - for example truncate the inode if it's
the last iput on unlinked file. Some filesystems depend on flusher thread
progressing (e.g. because they need to flush delay allocated blocks to reduce
allocation uncertainty) and so flusher thread doing truncate creates
interesting dependencies and possibilities for deadlocks.

We get rid of iput() in flusher thread by using the fact that I_SYNC inode
flag effectively pins the inode in memory. So if we take care to either hold
i_lock or have I_SYNC set, we can get away without taking inode reference
in writeback_sb_inodes().

As a side effect of these changes, we also fix possible use-after-free in
wb_writeback() because inode_wait_for_writeback() call could try to reacquire
i_lock on the inode that was already free.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
 fs/fs-writeback.c | 66 ++++++++++++++++++++++++++++++++++++++++++++-----------
 fs/inode.c        |  8 ++++++-
 2 files changed, 60 insertions(+), 14 deletions(-)

(limited to 'fs')

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5f2c68289610..8d2fb8c88cf3 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -326,9 +326,12 @@ static int write_inode(struct inode *inode, struct writeback_control *wbc)
 }
 
 /*
- * Wait for writeback on an inode to complete.
+ * Wait for writeback on an inode to complete. Called with i_lock held.
+ * Caller must make sure inode cannot go away when we drop i_lock.
  */
-static void inode_wait_for_writeback(struct inode *inode)
+static void __inode_wait_for_writeback(struct inode *inode)
+	__releases(inode->i_lock)
+	__acquires(inode->i_lock)
 {
 	DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
 	wait_queue_head_t *wqh;
@@ -341,6 +344,36 @@ static void inode_wait_for_writeback(struct inode *inode)
 	}
 }
 
+/*
+ * Wait for writeback on an inode to complete. Caller must have inode pinned.
+ */
+void inode_wait_for_writeback(struct inode *inode)
+{
+	spin_lock(&inode->i_lock);
+	__inode_wait_for_writeback(inode);
+	spin_unlock(&inode->i_lock);
+}
+
+/*
+ * Sleep until I_SYNC is cleared. This function must be called with i_lock
+ * held and drops it. It is aimed for callers not holding any inode reference
+ * so once i_lock is dropped, inode can go away.
+ */
+static void inode_sleep_on_writeback(struct inode *inode)
+	__releases(inode->i_lock)
+{
+	DEFINE_WAIT(wait);
+	wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
+	int sleep;
+
+	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
+	sleep = inode->i_state & I_SYNC;
+	spin_unlock(&inode->i_lock);
+	if (sleep)
+		schedule();
+	finish_wait(wqh, &wait);
+}
+
 /*
  * Find proper writeback list for the inode depending on its current state and
  * possibly also change of its state while we were doing writeback.  Here we
@@ -479,9 +512,11 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
 		if (wbc->sync_mode != WB_SYNC_ALL)
 			goto out;
 		/*
-		 * It's a data-integrity sync.  We must wait.
+		 * It's a data-integrity sync. We must wait. Since callers hold
+		 * inode reference or inode has I_WILL_FREE set, it cannot go
+		 * away under us.
 		 */
-		inode_wait_for_writeback(inode);
+		__inode_wait_for_writeback(inode);
 	}
 	WARN_ON(inode->i_state & I_SYNC);
 	/*
@@ -620,20 +655,28 @@ static long writeback_sb_inodes(struct super_block *sb,
 		}
 		spin_unlock(&wb->list_lock);
 
-		__iget(inode);
 		/*
 		 * We already requeued the inode if it had I_SYNC set and we
 		 * are doing WB_SYNC_NONE writeback. So this catches only the
 		 * WB_SYNC_ALL case.
 		 */
-		if (inode->i_state & I_SYNC)
-			inode_wait_for_writeback(inode);
+		if (inode->i_state & I_SYNC) {
+			/* Wait for I_SYNC. This function drops i_lock... */
+			inode_sleep_on_writeback(inode);
+			/* Inode may be gone, start again */
+			continue;
+		}
 		inode->i_state |= I_SYNC;
 		spin_unlock(&inode->i_lock);
+
 		write_chunk = writeback_chunk_size(wb->bdi, work);
 		wbc.nr_to_write = write_chunk;
 		wbc.pages_skipped = 0;
 
+		/*
+		 * We use I_SYNC to pin the inode in memory. While it is set
+		 * evict_inode() will wait so the inode cannot be freed.
+		 */
 		__writeback_single_inode(inode, wb, &wbc);
 
 		work->nr_pages -= write_chunk - wbc.nr_to_write;
@@ -645,10 +688,7 @@ static long writeback_sb_inodes(struct super_block *sb,
 		requeue_inode(inode, wb, &wbc);
 		inode_sync_complete(inode);
 		spin_unlock(&inode->i_lock);
-		spin_unlock(&wb->list_lock);
-		iput(inode);
-		cond_resched();
-		spin_lock(&wb->list_lock);
+		cond_resched_lock(&wb->list_lock);
 		/*
 		 * bail out to wb_writeback() often enough to check
 		 * background threshold and other termination conditions.
@@ -843,8 +883,8 @@ static long wb_writeback(struct bdi_writeback *wb,
 			inode = wb_inode(wb->b_more_io.prev);
 			spin_lock(&inode->i_lock);
 			spin_unlock(&wb->list_lock);
-			inode_wait_for_writeback(inode);
-			spin_unlock(&inode->i_lock);
+			/* This function drops i_lock... */
+			inode_sleep_on_writeback(inode);
 			spin_lock(&wb->list_lock);
 		}
 	}
diff --git a/fs/inode.c b/fs/inode.c
index 02c0fa5e16a4..f4e145016611 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -530,7 +530,13 @@ static void evict(struct inode *inode)
 
 	inode_sb_list_del(inode);
 
-	inode_sync_wait(inode);
+	/*
+	 * Wait for flusher thread to be done with the inode so that filesystem
+	 * does not start destroying it while writeback is still running. Since
+	 * the inode has I_FREEING set, flusher thread won't start new work on
+	 * the inode.  We just have to wait for running writeback to finish.
+	 */
+	inode_wait_for_writeback(inode);
 
 	if (op->evict_inode) {
 		op->evict_inode(inode);
-- 
cgit v1.2.1