linux-kernel - Re: [PATCH v3 1/6] locks: consolidate common code in the flock_to_posix

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Message-ID: <20131211225724.GB3483@fieldses.org>
Date:	Wed, 11 Dec 2013 17:57:24 -0500
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Jeff Layton <jlayton@...hat.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	nfs-ganesha-devel@...ts.sourceforge.net,
	samba-technical@...ts.samba.org
Subject: Re: [PATCH v3 1/6] locks: consolidate common code in the
 flock_to_posix_lock routines

On Wed, Dec 11, 2013 at 05:56:16PM -0500, J. Bruce Fields wrote:
> On Wed, Dec 11, 2013 at 02:07:41PM -0500, Jeff Layton wrote:
> > On Wed, 11 Dec 2013 10:19:31 -0500
> > "J. Bruce Fields" <bfields@...ldses.org> wrote:
> ...
> > > +	if (l->l_len > 0)
> > > +		fl->fl_end = fl->fl_start + l->l_len - 1;
> > > +	else if (l->l_len < 0) {
> > > +		fl->fl_end = start - 1;
> > 
> > Erm... I think this is not quite right...
> > 
> > "start" is uninitialized here. I think this should be:
> > 
> >     fl->fl_end = fl->fl_start - 1
> > 
> > With that too, we can get rid of the local "start" variable. I think
> > this may explain why I'm tripping over the BUG() in locks_remove_file.
> 
> Yep.
> 
> One other bug: I think l_start < 0 is actually fine in the
> SEEK_CUR/SEEK_END cases.
> 
> With that fixed and another comment (though I don't know how much it
> helps), it looks like the below.

Alternatively, maybe we could simplify?  (On top of the previous):

commit d4bf5cb021a3ac1ec07530ebda904e262cc89d11
Author: J. Bruce Fields <bfields@...hat.com>
Date:   Wed Dec 11 17:42:32 2013 -0500

    locks: simplify overflow checking
    
    Or maybe we don't actually care about indicating overflow in the 32-bit
    case: sure we could fail if e.g. f_pos+start or f_pos+start+len would
    exceed 32-bits, but do we really need to?
    
    Signed-off-by: J. Bruce Fields <bfields@...hat.com>

diff --git a/fs/locks.c b/fs/locks.c
index 39f2ca9..efbf577 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -344,8 +344,8 @@ static int assign_type(struct file_lock *fl, long type)
 	return 0;
 }
 
-static int flock_to_posix_lock_common(struct file *filp, struct file_lock *fl,
-					struct flock64 *l, loff_t offset_max)
+static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
+				 struct flock64 *l)
 {
 	switch (l->l_whence) {
 	case SEEK_SET:
@@ -360,12 +360,12 @@ static int flock_to_posix_lock_common(struct file *filp, struct file_lock *fl,
 	default:
 		return -EINVAL;
 	}
-	if (l->l_start > offset_max - fl->fl_start)
+	if (l->l_start > OFFSET_MAX - fl->fl_start)
 		return -EOVERFLOW;
 	fl->fl_start += l->l_start;
 	if (fl->fl_start < 0)
 		return -EINVAL;
-	if (l->l_len > offset_max - fl->fl_start)
+	if (l->l_len > OFFSET_MAX - fl->fl_start)
 		return -EOVERFLOW;
 	if (fl->fl_start + l->l_len < 0)
 		return -EINVAL;
@@ -403,22 +403,9 @@ static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
 		.l_len = l->l_len,
 	};
 
-	/*
-	 * The use of OFFT_OFFSET_MAX here ensures we return -EOVERFLOW
-	 * if the start or end of the lock could not be represented as
-	 * an off_t, following SUSv3.
-	 */
-	return flock_to_posix_lock_common(filp, fl, &ll, OFFT_OFFSET_MAX);
+	return flock64_to_posix_lock(filp, fl, &ll);
 }
 
-#if BITS_PER_LONG == 32
-static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
-				 struct flock64 *l)
-{
-	return flock_to_posix_lock_common(filp, fl, l, OFFSET_MAX);
-}
-#endif
-
 /* default lease lock manager operations */
 static void lease_break_callback(struct file_lock *fl)
 {
--
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