Re: [PATCH v7 10/11] xfs: make the calculation generic in xfs_sb_validate_fsb_count()

[Pankaj Raghav (Samsung)]

On Thu, Jun 13, 2024 at 10:45:45AM +0200, Christoph Hellwig wrote:
> > +	uint64_t		max_index;
> > +	uint64_t		max_bytes;
> > +
> >  	ASSERT(PAGE_SHIFT >= sbp->sb_blocklog);
> >  	ASSERT(sbp->sb_blocklog >= BBSHIFT);
> >  
> > +	if (check_shl_overflow(nblocks, sbp->sb_blocklog, &max_bytes))
> > +		return -EFBIG;
> > +
> >  	/* Limited by ULONG_MAX of page cache index */
> > -	if (nblocks >> (PAGE_SHIFT - sbp->sb_blocklog) > ULONG_MAX)
> > +	max_index = max_bytes >> PAGE_SHIFT;
> > +
> > +	if (max_index > ULONG_MAX)
> 
> Do we really need the max_index variable for a single user here?
> Or do you plan to add more uses of it later (can't really think of one
> though)?

Yeah, we could just inline it:

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index a99454208807..c6933440f806 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -132,7 +132,6 @@ xfs_sb_validate_fsb_count(
        xfs_sb_t        *sbp,
        uint64_t        nblocks)
 {
-       uint64_t                max_index;
        uint64_t                max_bytes;
 
        ASSERT(sbp->sb_blocklog >= BBSHIFT);
@@ -141,9 +140,7 @@ xfs_sb_validate_fsb_count(
                return -EFBIG;
 
        /* Limited by ULONG_MAX of page cache index */
-       max_index = max_bytes >> PAGE_SHIFT;
-
-       if (max_index > ULONG_MAX)
+       if (max_bytes >> PAGE_SHIFT > ULONG_MAX)
                return -EFBIG;
        return 0;
 }

>