Btrfs: Fix the unplug_io_fn to grab a consistent copy of page->mapping

Signed-off-by: Chris Mason <chris.mason@oracle.com>

2 files changed, 22 insertions, 7 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 19c258d2c7e2..1281c393c7e6 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -936,14 +936,25 @@ void btrfs_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
         struct inode *inode;
         struct extent_map_tree *em_tree;
         struct extent_map *em;
+        struct address_space *mapping;
         u64 offset;
 
+        /* the generic O_DIRECT read code does this */
         if (!page) {
                 __unplug_io_fn(bdi, page);
                 return;
         }
 
-        inode = page->mapping->host;
+        /*
+         * page->mapping may change at any time.  Get a consistent copy
+         * and use that for everything below
+         */
+        smp_mb();
+        mapping = page->mapping;
+        if (!mapping)
+                return;
+
+        inode = mapping->host;
         offset = page_offset(page);
 
         em_tree = &BTRFS_I(inode)->extent_tree;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index abfe86df02d2..d58b4d5a1fef 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -80,6 +80,7 @@ int btrfs_check_free_space(struct btrfs_root *root, u64 num_required,
         u64 total = btrfs_super_total_bytes(&root->fs_info->super_copy);
         u64 used = btrfs_super_bytes_used(&root->fs_info->super_copy);
         u64 thresh;
+        unsigned long flags;
         int ret = 0;
 
         if (for_del)
@@ -89,10 +90,10 @@ int btrfs_check_free_space(struct btrfs_root *root, u64 num_required,
 
         do_div(thresh, 100);
 
-        spin_lock(&root->fs_info->delalloc_lock);
+        spin_lock_irqsave(&root->fs_info->delalloc_lock, flags);
         if (used + root->fs_info->delalloc_bytes + num_required > thresh)
                 ret = -ENOSPC;
-        spin_unlock(&root->fs_info->delalloc_lock);
+        spin_unlock_irqrestore(&root->fs_info->delalloc_lock, flags);
         return ret;
 }
 
@@ -275,12 +276,13 @@ static int run_delalloc_range(struct inode *inode, u64 start, u64 end)
 int btrfs_set_bit_hook(struct inode *inode, u64 start, u64 end,
                        unsigned long old, unsigned long bits)
 {
+        unsigned long flags;
         if (!(old & EXTENT_DELALLOC) && (bits & EXTENT_DELALLOC)) {
                 struct btrfs_root *root = BTRFS_I(inode)->root;
-                spin_lock(&root->fs_info->delalloc_lock);
+                spin_lock_irqsave(&root->fs_info->delalloc_lock, flags);
                 BTRFS_I(inode)->delalloc_bytes += end - start + 1;
                 root->fs_info->delalloc_bytes += end - start + 1;
-                spin_unlock(&root->fs_info->delalloc_lock);
+                spin_unlock_irqrestore(&root->fs_info->delalloc_lock, flags);
         }
         return 0;
 }
@@ -290,7 +292,9 @@ int btrfs_clear_bit_hook(struct inode *inode, u64 start, u64 end,
 {
         if ((old & EXTENT_DELALLOC) && (bits & EXTENT_DELALLOC)) {
                 struct btrfs_root *root = BTRFS_I(inode)->root;
-                spin_lock(&root->fs_info->delalloc_lock);
+                unsigned long flags;
+
+                spin_lock_irqsave(&root->fs_info->delalloc_lock, flags);
                 if (end - start + 1 > root->fs_info->delalloc_bytes) {
                         printk("warning: delalloc account %Lu %Lu\n",
                                end - start + 1, root->fs_info->delalloc_bytes);
@@ -300,7 +304,7 @@ int btrfs_clear_bit_hook(struct inode *inode, u64 start, u64 end,
                         root->fs_info->delalloc_bytes -= end - start + 1;
                         BTRFS_I(inode)->delalloc_bytes -= end - start + 1;
                 }
-                spin_unlock(&root->fs_info->delalloc_lock);
+                spin_unlock_irqrestore(&root->fs_info->delalloc_lock, flags);
         }
         return 0;
 }