NFS: Remove BKL requirement from attribute updates

The main problem is dealing with inode->i_size: we need to set the
inode->i_lock on all attribute updates, and so vmtruncate won't cut it.
Make an NFS-private version of vmtruncate that has the necessary locking
semantics.

The result should be that the following inode attribute updates are
protected by inode->i_lock
	nfsi->cache_validity
	nfsi->read_cache_jiffies
	nfsi->attrtimeo
	nfsi->attrtimeo_timestamp
	nfsi->change_attr
	nfsi->last_updated
	nfsi->cache_change_attribute
	nfsi->access_cache
	nfsi->access_cache_entry_lru
	nfsi->access_cache_inode_lru
	nfsi->acl_access
	nfsi->acl_default
	nfsi->nfs_page_tree
	nfsi->ncommit
	nfsi->npages
	nfsi->open_files
	nfsi->silly_list
	nfsi->acl
	nfsi->open_states
	inode->i_size
	inode->i_atime
	inode->i_mtime
	inode->i_ctime
	inode->i_nlink
	inode->i_uid
	inode->i_gid

The following is protected by dir->i_mutex
	nfsi->cookieverf

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index feca8c648766..3229e217c773 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -133,16 +133,21 @@ static struct nfs_page *nfs_page_find_request(struct page *page)
 static void nfs_grow_file(struct page *page, unsigned int offset, unsigned int count)
 {
 	struct inode *inode = page->mapping->host;
-	loff_t end, i_size = i_size_read(inode);
-	pgoff_t end_index = (i_size - 1) >> PAGE_CACHE_SHIFT;
+	loff_t end, i_size;
+	pgoff_t end_index;
 
+	spin_lock(&inode->i_lock);
+	i_size = i_size_read(inode);
+	end_index = (i_size - 1) >> PAGE_CACHE_SHIFT;
 	if (i_size > 0 && page->index < end_index)
-		return;
+		goto out;
 	end = ((loff_t)page->index << PAGE_CACHE_SHIFT) + ((loff_t)offset+count);
 	if (i_size >= end)
-		return;
-	nfs_inc_stats(inode, NFSIOS_EXTENDWRITE);
+		goto out;
 	i_size_write(inode, end);
+	nfs_inc_stats(inode, NFSIOS_EXTENDWRITE);
+out:
+	spin_unlock(&inode->i_lock);
 }
 
 /* A writeback failed: mark the page as bad, and invalidate the page cache */