linux-kernel - Re: 2.6.19-rc2-mm2 : empty files on vfat file system

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Message-ID: <87hcxxx0dv.fsf@duaron.myhome.or.jp>
Date:	Sat, 21 Oct 2006 22:29:48 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Damien Wyart <damien.wyart@...e.fr>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...e.de>, Andrew Morton <akpm@...l.org>
Subject: Re: 2.6.19-rc2-mm2 : empty files on vfat file system

OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> writes:

> Damien Wyart <damien.wyart@...e.fr> writes:
>
>> I have noticed something strange (and bad :) since using 2.6.19-rc2-mm2
>> (the problem is NOT present on 2.6.19-rc2-mm1 ; do not know for
>> mainline, I have not been able to test yet, but I think there have not
>> been recent changes in this area) : writing a file to a vfat
>> fs (fat 32) writes it, but with size 0 and no content. All this is
>> silent : no error message, nothing in the logs. After several attempts,
>> I checked the fs with fsck.vfat and it reported errors about some of the
>> files and told it was truncating them to size 0 (but their displayed
>> size was already 0, btw).
>
> diff -puN fs/fat/inode.c~fs-prepare_write-fixes fs/fat/inode.c
> --- a/fs/fat/inode.c~fs-prepare_write-fixes
> +++ a/fs/fat/inode.c
> @@ -150,7 +150,11 @@ static int fat_commit_write(struct file 
>  			    unsigned from, unsigned to)
>  {
>  	struct inode *inode = page->mapping->host;
> -	int err = generic_commit_write(file, page, from, to);
> +	int err;
> +	if (to - from > 0)
> +		return 0;
> +
> +	err = generic_commit_write(file, page, from, to);
>  	if (!err && !(MSDOS_I(inode)->i_attrs & ATTR_ARCH)) {
>  		inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
>  		MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
>
> This change does't update ->i_size. Could you just delete, and test it?
> Anyway, this seems wrong even if it's "if ((to - from) == 0)".  The zero
> range is valid for cont_prepare_write()...

s/cont_prepare_write/generic_cont_expand/.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
-
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