Re: O_DIRECT wierd behavior..

From: GOTO Masanori (gotom@debian.org)
Date: Sun Dec 16 2001 - 03:17:33 EST


At Sat, 15 Dec 2001 21:59:06 -0800,
Andrew Morton wrote:
> Then the kernel screws up the error handling, and ends up
> setting the file size to -EINVAL (ie: rather large).
>
> 1: We're testing `written >= 0', but it is unsigned (!). In two
> places.
>
> This one, IMO is a gcc shortcoming. The compiler is capable of warning
> about expressions which always evaluate to true or false in `if' statements,
> but turning this on also enables lots of things you don't want it to warn about.
> gcc needs to provide finer control of its warning capabilities. I patched
> gcc-2.7.2.3 to do this ages back and it was very useful.
>
> 2: If generic_osync_inode() returns an error, we fail to report it. In
> two places.
>
> Here's a quick fix. It needs a review.
>
> --- linux-2.4.17-rc1/mm/filemap.c Thu Dec 13 14:07:55 2001
> +++ linux-akpm/mm/filemap.c Sat Dec 15 21:52:06 2001
> @@ -3038,8 +3038,11 @@ unlock:
> /* For now, when the user asks for O_SYNC, we'll actually
> * provide O_DSYNC. */
> if (status >= 0) {
> - if ((file->f_flags & O_SYNC) || IS_SYNC(inode))
> + if ((file->f_flags & O_SYNC) || IS_SYNC(inode)) {
> status = generic_osync_inode(inode, OSYNC_METADATA|OSYNC_DATA);
> + if (status < 0)
> + written = 0; /* Return the right thing */
> + }
> }

Right. If generic_osync_inode returns error, it must be needed.
This patch seems ok than my patch...

-- gotom
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