vfs: don't allow writes to swap files

Don't let userspace write to an active swap file because the kernel
effectively has a long term lease on the storage and things could get
seriously corrupted if we let this happen.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 56b8e358af5c..a2e3d446ba8e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3547,4 +3547,15 @@ static inline void simple_fill_fsxattr(struct fsxattr *fa, __u32 xflags)
         fa->fsx_xflags = xflags;
 }
 
+/*
+ * Flush file data before changing attributes.  Caller must hold any locks
+ * required to prevent further writes to this file until we're done setting
+ * flags.
+ */
+static inline int inode_drain_writes(struct inode *inode)
+{
+        inode_dio_wait(inode);
+        return filemap_write_and_wait(inode->i_mapping);
+}
+
 #endif /* _LINUX_FS_H */