linux-kernel - [PATCH v3 2/2] drivers: staging: lustre: Track sign separately

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Date:	Sun, 21 Dec 2014 11:04:05 -0600
From:	Chris Rorvick <chris@...vick.com>
To:	Oleg Drokin <oleg.drokin@...el.com>,
	Andreas Dilger <andreas.dilger@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Chris Rorvick <chris@...vick.com>,
	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>,
	Julia Lawall <Julia.Lawall@...6.fr>,
	Greg Donald <gdonald@...il.com>,
	"John L. Hammond" <john.hammond@...el.com>,
	Andriy Skulysh <Andriy_Skulysh@...atex.com>,
	Fabian Frederick <fabf@...net.be>,
	James Simmons <uja.ornl@...il.com>, HPDD-discuss@...ts.01.org,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 2/2] drivers: staging: lustre: Track sign separately

The `mult' parameter is negated if the user data begins with a '-' so
that the final value has the appropriate sign.  But `mult' is only used
if the user data does not include a "units" suffix.  In this case,
`mult' is overridden with the numeric scale conveyed by the units suffix,
but retains the sign of the original value.

Having `mult' serving double-duty works but is confusing.  Use a new
local variable to store the sign of the user data instead.  This also
fixes a pitfall of passing 0 to `mult', expecting it to be ignored when
a units suffix is specified, but having the effect of taking the
absolute value of the user-provided data.

Signed-off-by: Chris Rorvick <chris@...vick.com>
Reviewed-by: Andreas Dilger <andreas.dilger@...el.com>
---
 drivers/staging/lustre/lustre/obdclass/lprocfs_status.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c
index a7b270e..22e13f0 100644
--- a/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c
+++ b/drivers/staging/lustre/lustre/obdclass/lprocfs_status.c
@@ -1862,6 +1862,7 @@ int lprocfs_write_frac_u64_helper(const char *buffer, unsigned long count,
 	char kernbuf[22], *end, *pbuf;
 	__u64 whole, frac = 0, units;
 	unsigned frac_d = 1;
+	int sign = 1;
 
 	if (count > (sizeof(kernbuf) - 1))
 		return -EINVAL;
@@ -1872,7 +1873,7 @@ int lprocfs_write_frac_u64_helper(const char *buffer, unsigned long count,
 	kernbuf[count] = '\0';
 	pbuf = kernbuf;
 	if (*pbuf == '-') {
-		mult = -mult;
+		sign = -1;
 		pbuf++;
 	}
 
@@ -1909,11 +1910,11 @@ int lprocfs_write_frac_u64_helper(const char *buffer, unsigned long count,
 	}
 	/* Specified units override the multiplier */
 	if (units > 1)
-		mult = mult < 0 ? -units : units;
+		mult = units;
 
 	frac *= mult;
 	do_div(frac, frac_d);
-	*val = whole * mult + frac;
+	*val = sign * (whole * mult + frac);
 	return 0;
 }
 EXPORT_SYMBOL(lprocfs_write_frac_u64_helper);
-- 
2.1.0

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