From 14da9200140f8d722ad1767dfabadebd8b34f2ad Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 12 Jun 2012 16:20:37 +0200 Subject: fs: Protect write paths by sb_start_write - sb_end_write There are several entry points which dirty pages in a filesystem. mmap (handled by block_page_mkwrite()), buffered write (handled by __generic_file_aio_write()), splice write (generic_file_splice_write), truncate, and fallocate (these can dirty last partial page - handled inside each filesystem separately). Protect these places with sb_start_write() and sb_end_write(). ->page_mkwrite() calls are particularly complex since they are called with mmap_sem held and thus we cannot use standard sb_start_write() due to lock ordering constraints. We solve the problem by using a special freeze protection sb_start_pagefault() which ranks below mmap_sem. BugLink: https://bugs.launchpad.net/bugs/897421 Tested-by: Kamal Mostafa Tested-by: Peter M. Petrakis Tested-by: Dann Frazier Tested-by: Massimo Morana Signed-off-by: Jan Kara Signed-off-by: Al Viro --- fs/splice.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'fs/splice.c') diff --git a/fs/splice.c b/fs/splice.c index 7bf08fa22ec9..41514dd89462 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -996,6 +996,8 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out, }; ssize_t ret; + sb_start_write(inode->i_sb); + pipe_lock(pipe); splice_from_pipe_begin(&sd); @@ -1034,6 +1036,7 @@ generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out, *ppos += ret; balance_dirty_pages_ratelimited_nr(mapping, nr_pages); } + sb_end_write(inode->i_sb); return ret; } -- cgit