[RFC PATCH v2 09/16] 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/inode.c         | 19 ++++++++++++++++++-
 fs/xfs/xfs_file.c  |  2 +-
 include/linux/fs.h |  1 +
 3 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index fd18b2c1b7c4..40941feaec8d 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2126,6 +2126,13 @@ EXPORT_SYMBOL(file_update_time);
 
 /* Caller must hold the file's inode lock */
 int file_modified(struct file *file)
+{
+	return file_modified_async(file, 0);
+}
+EXPORT_SYMBOL(file_modified);
+
+/* Caller must hold the file's inode lock */
+int file_modified_async(struct file *file, int flags)
 {
 	int ret;
 	struct dentry *dentry = file_dentry(file);
@@ -2140,6 +2147,9 @@ int file_modified(struct file *file)
 	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;
@@ -2148,10 +2158,17 @@ int file_modified(struct file *file)
 	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);
 }
-EXPORT_SYMBOL(file_modified);
+EXPORT_SYMBOL(file_modified_async);
 
 int inode_needs_sync(struct inode *inode)
 {
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 5bddb1e9e0b3..793918c83755 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -410,7 +410,7 @@ xfs_file_write_checks(
 		spin_unlock(&ip->i_flags_lock);
 
 out:
-	return file_modified(file);
+	return file_modified_async(file, iocb->ki_flags);
 }
 
 static int
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3da641dfa6d9..5f3aaf61fb4b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2385,6 +2385,7 @@ static inline void file_accessed(struct file *file)
 }
 
 extern int file_modified(struct file *file);
+extern int file_modified_async(struct file *file, int flags);
 
 int sync_inode_metadata(struct inode *inode, int wait);
 
-- 
2.30.2