From: Jan Kara Date: Mon, 13 Jun 2011 22:58:27 +0000 (+0200) Subject: vfs: Fix data corruption after failed write in __block_write_begin() X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=f9f07b6c1372b1436aa6b45333445b443ffd8c95;p=openwrt%2Fstaging%2Fblogic.git vfs: Fix data corruption after failed write in __block_write_begin() I've got a report of a file corruption from fsxlinux on ext3. The important operations to the page were: mapwrite to a hole partial write to the page read - found the page zeroed from the end of the normal write The culprit seems to be that if get_block() fails in __block_write_begin() (e.g. transient ENOSPC in ext3), the function does ClearPageUptodate(page). Thus when we retry the write, the logic in __block_write_begin() thinks zeroing of the page is needed and overwrites old data. In fact, I don't see why we should ever need to zero the uptodate bit here - either the page was uptodate when we entered __block_write_begin() and it should stay so when we leave it, or it was not uptodate and noone had right to set it uptodate during __block_write_begin() so it remains !uptodate when we leave as well. So just remove clearing of the bit. Signed-off-by: Jan Kara Signed-off-by: Al Viro --- diff --git a/fs/buffer.c b/fs/buffer.c index 49c9aada0374..1a80b048ade8 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1902,10 +1902,8 @@ int __block_write_begin(struct page *page, loff_t pos, unsigned len, if (!buffer_uptodate(*wait_bh)) err = -EIO; } - if (unlikely(err)) { + if (unlikely(err)) page_zero_new_buffers(page, from, to); - ClearPageUptodate(page); - } return err; } EXPORT_SYMBOL(__block_write_begin);