introduce I_SYNC

I_LOCK was used for several unrelated purposes, which caused deadlock
situations in certain filesystems as a side effect.  One of the purposes
now uses the new I_SYNC bit.

Also document the various bits and change their order from historical to
logical.

[bunk@stusta.de: make fs/inode.c:wake_up_inode() static]
Signed-off-by: Joern Engel <joern@wohnheim.fh-wedel.de>
Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: David Chinner <dgc@sgi.com>
Cc: Anton Altaparmakov <aia21@cam.ac.uk>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 24 insertions, 15 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 71c158ac60a3..686734ff973d 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -100,11 +100,11 @@ void __mark_inode_dirty(struct inode *inode, int flags)
                 inode->i_state |= flags;
 
                 /*
-                 * If the inode is locked, just update its dirty state. 
+                 * If the inode is being synced, just update its dirty state.
                  * The unlocker will place the inode on the appropriate
                  * superblock list, based upon its state.
                  */
-                if (inode->i_state & I_LOCK)
+                if (inode->i_state & I_SYNC)
                         goto out;
 
                 /*
@@ -172,6 +172,15 @@ static void requeue_io(struct inode *inode)
         list_move(&inode->i_list, &inode->i_sb->s_more_io);
 }
 
+static void inode_sync_complete(struct inode *inode)
+{
+        /*
+         * Prevent speculative execution through spin_unlock(&inode_lock);
+         */
+        smp_mb();
+        wake_up_bit(&inode->i_state, __I_SYNC);
+}
+
 /*
  * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
  */
@@ -225,11 +234,11 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
         int wait = wbc->sync_mode == WB_SYNC_ALL;
         int ret;
 
-        BUG_ON(inode->i_state & I_LOCK);
+        BUG_ON(inode->i_state & I_SYNC);
 
-        /* Set I_LOCK, reset I_DIRTY */
+        /* Set I_SYNC, reset I_DIRTY */
         dirty = inode->i_state & I_DIRTY;
-        inode->i_state |= I_LOCK;
+        inode->i_state |= I_SYNC;
         inode->i_state &= ~I_DIRTY;
 
         spin_unlock(&inode_lock);
@@ -250,7 +259,7 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
         }
 
         spin_lock(&inode_lock);
-        inode->i_state &= ~I_LOCK;
+        inode->i_state &= ~I_SYNC;
         if (!(inode->i_state & I_FREEING)) {
                 if (!(inode->i_state & I_DIRTY) &&
                     mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
@@ -305,7 +314,7 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
                         list_move(&inode->i_list, &inode_unused);
                 }
         }
-        wake_up_inode(inode);
+        inode_sync_complete(inode);
         return ret;
 }
 
@@ -324,7 +333,7 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
         else
                 WARN_ON(inode->i_state & I_WILL_FREE);
 
-        if ((wbc->sync_mode != WB_SYNC_ALL) && (inode->i_state & I_LOCK)) {
+        if ((wbc->sync_mode != WB_SYNC_ALL) && (inode->i_state & I_SYNC)) {
                 struct address_space *mapping = inode->i_mapping;
                 int ret;
 
@@ -350,16 +359,16 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
         /*
          * It's a data-integrity sync.  We must wait.
          */
-        if (inode->i_state & I_LOCK) {
-                DEFINE_WAIT_BIT(wq, &inode->i_state, __I_LOCK);
+        if (inode->i_state & I_SYNC) {
+                DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
 
-                wqh = bit_waitqueue(&inode->i_state, __I_LOCK);
+                wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
                 do {
                         spin_unlock(&inode_lock);
                         __wait_on_bit(wqh, &wq, inode_wait,
                                                         TASK_UNINTERRUPTIBLE);
                         spin_lock(&inode_lock);
-                } while (inode->i_state & I_LOCK);
+                } while (inode->i_state & I_SYNC);
         }
         return __sync_single_inode(inode, wbc);
 }
@@ -392,7 +401,7 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
  * The inodes to be written are parked on sb->s_io.  They are moved back onto
  * sb->s_dirty as they are selected for writing.  This way, none can be missed
  * on the writer throttling path, and we get decent balancing between many
- * throttled threads: we don't want them all piling up on __wait_on_inode.
+ * throttled threads: we don't want them all piling up on inode_sync_wait.
  */
 static void
 sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
@@ -661,7 +670,7 @@ int write_inode_now(struct inode *inode, int sync)
         ret = __writeback_single_inode(inode, &wbc);
         spin_unlock(&inode_lock);
         if (sync)
-                wait_on_inode(inode);
+                inode_sync_wait(inode);
         return ret;
 }
 EXPORT_SYMBOL(write_inode_now);
@@ -736,7 +745,7 @@ int generic_osync_inode(struct inode *inode, struct address_space *mapping, int
                         err = err2;
         }
         else
-                wait_on_inode(inode);
+                inode_sync_wait(inode);
 
         return err;
 }