[PATCH] Prevent dirtying a page when ext4 F.S is frozen
From: Surbhi Palande <hidden>
Date: 2011-05-03 13:08:48
Also in:
linux-fsdevel
Subsystem:
ext4 file system, filesystems (vfs and infrastructure), the rest · Maintainers:
"Theodore Ts'o", Alexander Viro, Christian Brauner, Linus Torvalds
Prevent dirtying a page when ext4 F.S is frozen. Also take the write semaphore sb->s_umount to prevent a F.S freeze from racing with the page dirtying process. Without this we can end up dirtying a page while a F.S freeze happened because of preemption. Signed-off-by: Surbhi Palande <redacted> --- fs/ext4/inode.c | 35 ++++++++++++++++++++++++++++++++++- 1 files changed, 34 insertions(+), 1 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f2fa5e8..db3f99d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c@@ -3827,8 +3827,41 @@ static ssize_t ext4_direct_IO(int rw, struct kiocb *iocb, */ static int ext4_journalled_set_page_dirty(struct page *page) { + int ret=0; + struct inode * inode = NULL; + struct super_block * sb = NULL; + + if(likely((page->mapping) && (page->mapping->host))){ + inode = page->mapping->host; + if(likely(inode->i_sb)){ + sb = inode->i_sb; + /* we do not want a freeze to start now if F.S is not + * already frozen*/ + down_write(&sb->s_umount); + if(sb->s_frozen != SB_UNFROZEN) { + /* F.S is frozen. + * we dont want to sleep with s_umount held. + * Or else we might race with thaw_super */ + up_write(&sb->s_umount); + vfs_check_frozen(sb, SB_FREEZE_WRITE); + /* F.S is no more frozen. We do not want the + * FS freeze to begin after this point + */ + down_write(&sb->s_umount); + } + } + } SetPageChecked(page); - return __set_page_dirty_nobuffers(page); + ret = __set_page_dirty_nobuffers(page); + if(likely((page->mapping) && (page->mapping->host))){ + if(likely(inode->i_sb)){ + up_write(&sb->s_umount); + /* If we freeze after this point, the dirtied page can + * be flushed out! + */ + } + } + return ret; } static const struct address_space_operations ext4_ordered_aops = {
--
1.7.1