[RFC PATCH v1 10/18] xfs: Enable async write file modification handling.

[Stefan Roesch <shr@fb.com>]

This modifies xfs write checks to return -EAGAIN if the request either
requires to remove privileges or needs to update the file modification
time. This is required for async buffered writes, so the request gets
handled in the io worker.

Signed-off-by: Stefan Roesch <shr@fb.com>
---
 fs/xfs/xfs_file.c | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 5bddb1e9e0b3..6f9da1059e8b 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -299,6 +299,43 @@ xfs_file_read_iter(
 	return ret;
 }
 
+static int xfs_file_modified(struct file *file, int flags)
+{
+	int ret;
+	struct dentry *dentry = file_dentry(file);
+	struct inode *inode = file_inode(file);
+	struct timespec64 now = current_time(inode);
+
+	/*
+	 * Clear the security bits if the process is not being run by root.
+	 * This keeps people from modifying setuid and setgid binaries.
+	 */
+	ret = need_file_remove_privs(inode, dentry);
+	if (ret < 0) {
+		return ret;
+	} else if (ret > 0) {
+		if (flags & IOCB_NOWAIT)
+			return -EAGAIN;
+
+		ret = do_file_remove_privs(file, inode, dentry, ret);
+		if (ret)
+			return ret;
+	}
+
+	ret = need_file_update_time(inode, file, &now);
+	if (ret <= 0)
+		return ret;
+	if (flags & IOCB_NOWAIT) {
+		if (IS_PENDING_TIME(inode))
+			return 0;
+
+		inode->i_flags |= S_PENDING_TIME;
+		return -EAGAIN;
+	}
+
+	return do_file_update_time(inode, file, &now, ret);
+}
+
 /*
  * Common pre-write limit and setup checks.
  *
@@ -410,7 +447,7 @@ xfs_file_write_checks(
 		spin_unlock(&ip->i_flags_lock);
 
 out:
-	return file_modified(file);
+	return xfs_file_modified(file, iocb->ki_flags);
 }
 
 static int
-- 
2.30.2