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

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

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 19c258d..1281c39 100644 (file)
--- 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 abfe86d..d58b4d5 100644 (file)
--- 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;
 }