4 files changed, 93 insertions, 2 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 0f9006714230..02ebb1f1d3b0 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2194,6 +2194,52 @@ int generic_commit_write(struct file *file, struct page *page,
         return 0;
 }
 
+/*
+ * block_page_mkwrite() is not allowed to change the file size as it gets
+ * called from a page fault handler when a page is first dirtied. Hence we must
+ * be careful to check for EOF conditions here. We set the page up correctly
+ * for a written page which means we get ENOSPC checking when writing into
+ * holes and correct delalloc and unwritten extent mapping on filesystems that
+ * support these features.
+ *
+ * We are not allowed to take the i_mutex here so we have to play games to
+ * protect against truncate races as the page could now be beyond EOF.  Because
+ * vmtruncate() writes the inode size before removing pages, once we have the
+ * page lock we can determine safely if the page is beyond EOF. If it is not
+ * beyond EOF, then the page is guaranteed safe against truncation until we
+ * unlock the page.
+ */
+int
+block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
+                   get_block_t get_block)
+{
+        struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
+        unsigned long end;
+        loff_t size;
+        int ret = -EINVAL;
+
+        lock_page(page);
+        size = i_size_read(inode);
+        if ((page->mapping != inode->i_mapping) ||
+            ((page->index << PAGE_CACHE_SHIFT) > size)) {
+                /* page got truncated out from underneath us */
+                goto out_unlock;
+        }
+
+        /* page is wholly or partially inside EOF */
+        if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
+                end = size & ~PAGE_CACHE_MASK;
+        else
+                end = PAGE_CACHE_SIZE;
+
+        ret = block_prepare_write(page, 0, end, get_block);
+        if (!ret)
+                ret = block_commit_write(page, 0, end);
+
+out_unlock:
+        unlock_page(page);
+        return ret;
+}
 
 /*
  * nobh_prepare_write()'s prereads are special: the buffer_heads are freed
@@ -2977,6 +3023,7 @@ EXPORT_SYMBOL(__brelse);
 EXPORT_SYMBOL(__wait_on_buffer);
 EXPORT_SYMBOL(block_commit_write);
 EXPORT_SYMBOL(block_prepare_write);
+EXPORT_SYMBOL(block_page_mkwrite);
 EXPORT_SYMBOL(block_read_full_page);
 EXPORT_SYMBOL(block_sync_page);
 EXPORT_SYMBOL(block_truncate_page);
diff --git a/fs/xfs/linux-2.6/xfs_file.c b/fs/xfs/linux-2.6/xfs_file.c
index 2d4be2f247b2..0d4001eafd16 100644
--- a/fs/xfs/linux-2.6/xfs_file.c
+++ b/fs/xfs/linux-2.6/xfs_file.c
@@ -413,6 +413,20 @@ xfs_file_open_exec(
 }
 #endif /* HAVE_FOP_OPEN_EXEC */
 
+/*
+ * mmap()d file has taken write protection fault and is being made
+ * writable. We can set the page state up correctly for a writable
+ * page, which means we can do correct delalloc accounting (ENOSPC
+ * checking!) and unwritten extent mapping.
+ */
+STATIC int
+xfs_vm_page_mkwrite(
+        struct vm_area_struct   *vma,
+        struct page             *page)
+{
+        return block_page_mkwrite(vma, page, xfs_get_blocks);
+}
+
 const struct file_operations xfs_file_operations = {
         .llseek         = generic_file_llseek,
         .read           = do_sync_read,
@@ -465,11 +479,13 @@ const struct file_operations xfs_dir_file_operations = {
 
 static struct vm_operations_struct xfs_file_vm_ops = {
         .fault          = filemap_fault,
+        .page_mkwrite   = xfs_vm_page_mkwrite,
 };
 
 #ifdef CONFIG_XFS_DMAPI
 static struct vm_operations_struct xfs_dmapi_file_vm_ops = {
         .fault          = xfs_vm_fault,
+        .page_mkwrite   = xfs_vm_page_mkwrite,
 #ifdef HAVE_VMOP_MPROTECT
         .mprotect       = xfs_vm_mprotect,
 #endif
diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
index 79b522779aa4..1a5ad8cd97b0 100644
--- a/fs/xfs/xfs_vnodeops.c
+++ b/fs/xfs/xfs_vnodeops.c
@@ -589,7 +589,30 @@ xfs_setattr(
                         code = xfs_igrow_start(ip, vap->va_size, credp);
                 }
                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
-                vn_iowait(vp); /* wait for the completion of any pending DIOs */
+
+                /*
+                 * We are going to log the inode size change in this
+                 * transaction so any previous writes that are beyond the on
+                 * disk EOF and the new EOF that have not been written out need
+                 * to be written here. If we do not write the data out, we
+                 * expose ourselves to the null files problem.
+                 *
+                 * Only flush from the on disk size to the smaller of the in
+                 * memory file size or the new size as that's the range we
+                 * really care about here and prevents waiting for other data
+                 * not within the range we care about here.
+                 */
+                if (!code &&
+                    (ip->i_size != ip->i_d.di_size) &&
+                    (vap->va_size > ip->i_d.di_size)) {
+                        code = bhv_vop_flush_pages(XFS_ITOV(ip),
+                                        ip->i_d.di_size, vap->va_size,
+                                        XFS_B_ASYNC, FI_NONE);
+                }
+
+                /* wait for all I/O to complete */
+                vn_iowait(vp);
+
                 if (!code)
                         code = xfs_itruncate_data(ip, vap->va_size);
                 if (code) {
@@ -4434,9 +4457,12 @@ xfs_free_file_space(
         while (!error && !done) {
 
                 /*
-                 * allocate and setup the transaction
+                 * allocate and setup the transaction. Allow this
+                 * transaction to dip into the reserve blocks to ensure
+                 * the freeing of the space succeeds at ENOSPC.
                  */
                 tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);
+                tp->t_flags |= XFS_TRANS_RESERVE;
                 error = xfs_trans_reserve(tp,
                                           resblks,
                                           XFS_WRITE_LOG_RES(mp),
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 5c6e12853a9b..35cadad84b14 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -209,6 +209,8 @@ int cont_prepare_write(struct page*, unsigned, unsigned, get_block_t*,
 int generic_cont_expand(struct inode *inode, loff_t size);
 int generic_cont_expand_simple(struct inode *inode, loff_t size);
 int block_commit_write(struct page *page, unsigned from, unsigned to);
+int block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
+                                get_block_t get_block);
 void block_sync_page(struct page *);
 sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
 int generic_commit_write(struct file *, struct page *, unsigned, unsigned);