| Message ID | 20171213201743.27324-1-colin.king@canonical.com |
|---|---|
| State | Rejected |
| Delegated to: | Boris Brezillon |
| Headers | show |
| Series | [mtd-next] mtd: nand: remove redundant check of len | expand |
On Wed, 13 Dec 2017 20:17:43 +0000 Colin King <colin.king@canonical.com> wrote: > From: Colin Ian King <colin.king@canonical.com> > > The check of len being zero is redundant as it has already been > sanity checked for this value at the start of the function. Hence > it is impossible for this test to be true and so the redundant > code can be removed. Nope, it's not the same test, the initial test is if (len && !buf) not if (len) So this test is not redundant. > > Detected by CoverityScan, CID#1462748 ("Logically dead code") > > Signed-off-by: Colin Ian King <colin.king@canonical.com> > --- > drivers/mtd/nand/nand_base.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c > index afd5e18db81c..9daaa23db943 100644 > --- a/drivers/mtd/nand/nand_base.c > +++ b/drivers/mtd/nand/nand_base.c > @@ -1507,10 +1507,6 @@ static int nand_read_param_page_op(struct nand_chip *chip, u8 page, void *buf, > }; > struct nand_operation op = NAND_OPERATION(instrs); > > - /* Drop the DATA_IN instruction if len is set to 0. */ > - if (!len) > - op.ninstrs--; > - > return nand_exec_op(chip, &op); > } >
On 13/12/17 20:24, Boris Brezillon wrote: > On Wed, 13 Dec 2017 20:17:43 +0000 > Colin King <colin.king@canonical.com> wrote: > >> From: Colin Ian King <colin.king@canonical.com> >> >> The check of len being zero is redundant as it has already been >> sanity checked for this value at the start of the function. Hence >> it is impossible for this test to be true and so the redundant >> code can be removed. > > Nope, it's not the same test, the initial test is > > if (len && !buf) Ah, the current tip from linux-next has: 1912 if (!len || !buf) 1913 return -EINVAL; ..so I guess that's why it got picked up by static analysis. > > not > > if (len) > > So this test is not redundant. > >> >> Detected by CoverityScan, CID#1462748 ("Logically dead code") >> >> Signed-off-by: Colin Ian King <colin.king@canonical.com> >> --- >> drivers/mtd/nand/nand_base.c | 4 ---- >> 1 file changed, 4 deletions(-) >> >> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c >> index afd5e18db81c..9daaa23db943 100644 >> --- a/drivers/mtd/nand/nand_base.c >> +++ b/drivers/mtd/nand/nand_base.c >> @@ -1507,10 +1507,6 @@ static int nand_read_param_page_op(struct nand_chip *chip, u8 page, void *buf, >> }; >> struct nand_operation op = NAND_OPERATION(instrs); >> >> - /* Drop the DATA_IN instruction if len is set to 0. */ >> - if (!len) >> - op.ninstrs--; >> - >> return nand_exec_op(chip, &op); >> } >> >
On Wed, 13 Dec 2017 20:30:04 +0000 Colin Ian King <colin.king@canonical.com> wrote: > On 13/12/17 20:24, Boris Brezillon wrote: > > On Wed, 13 Dec 2017 20:17:43 +0000 > > Colin King <colin.king@canonical.com> wrote: > > > >> From: Colin Ian King <colin.king@canonical.com> > >> > >> The check of len being zero is redundant as it has already been > >> sanity checked for this value at the start of the function. Hence > >> it is impossible for this test to be true and so the redundant > >> code can be removed. > > > > Nope, it's not the same test, the initial test is > > > > if (len && !buf) > > Ah, the current tip from linux-next has: > > 1912 if (!len || !buf) > 1913 return -EINVAL; > > ..so I guess that's why it got picked up by static analysis. Hm, that's weird, that's not what I see [1] in linux-next. [1]https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/mtd/nand/nand_base.c#n1488 > > > > > not > > > > if (len) > > > > So this test is not redundant. > > > >> > >> Detected by CoverityScan, CID#1462748 ("Logically dead code") > >> > >> Signed-off-by: Colin Ian King <colin.king@canonical.com> > >> --- > >> drivers/mtd/nand/nand_base.c | 4 ---- > >> 1 file changed, 4 deletions(-) > >> > >> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c > >> index afd5e18db81c..9daaa23db943 100644 > >> --- a/drivers/mtd/nand/nand_base.c > >> +++ b/drivers/mtd/nand/nand_base.c > >> @@ -1507,10 +1507,6 @@ static int nand_read_param_page_op(struct nand_chip *chip, u8 page, void *buf, > >> }; > >> struct nand_operation op = NAND_OPERATION(instrs); > >> > >> - /* Drop the DATA_IN instruction if len is set to 0. */ > >> - if (!len) > >> - op.ninstrs--; > >> - > >> return nand_exec_op(chip, &op); > >> } > >> > > >
On 13/12/17 20:38, Boris Brezillon wrote: > On Wed, 13 Dec 2017 20:30:04 +0000 > Colin Ian King <colin.king@canonical.com> wrote: > >> On 13/12/17 20:24, Boris Brezillon wrote: >>> On Wed, 13 Dec 2017 20:17:43 +0000 >>> Colin King <colin.king@canonical.com> wrote: >>> >>>> From: Colin Ian King <colin.king@canonical.com> >>>> >>>> The check of len being zero is redundant as it has already been >>>> sanity checked for this value at the start of the function. Hence >>>> it is impossible for this test to be true and so the redundant >>>> code can be removed. >>> >>> Nope, it's not the same test, the initial test is >>> >>> if (len && !buf) >> >> Ah, the current tip from linux-next has: >> >> 1912 if (!len || !buf) >> 1913 return -EINVAL; >> >> ..so I guess that's why it got picked up by static analysis. > > Hm, that's weird, that's not what I see [1] in linux-next. I see my mistake, I fixed the *wrong* function, I'll send a v2. Doh. > > [1]https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/mtd/nand/nand_base.c#n1488 > >> >>> >>> not >>> >>> if (len) >>> >>> So this test is not redundant. >>> >>>> >>>> Detected by CoverityScan, CID#1462748 ("Logically dead code") >>>> >>>> Signed-off-by: Colin Ian King <colin.king@canonical.com> >>>> --- >>>> drivers/mtd/nand/nand_base.c | 4 ---- >>>> 1 file changed, 4 deletions(-) >>>> >>>> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c >>>> index afd5e18db81c..9daaa23db943 100644 >>>> --- a/drivers/mtd/nand/nand_base.c >>>> +++ b/drivers/mtd/nand/nand_base.c >>>> @@ -1507,10 +1507,6 @@ static int nand_read_param_page_op(struct nand_chip *chip, u8 page, void *buf, >>>> }; >>>> struct nand_operation op = NAND_OPERATION(instrs); >>>> >>>> - /* Drop the DATA_IN instruction if len is set to 0. */ >>>> - if (!len) >>>> - op.ninstrs--; >>>> - >>>> return nand_exec_op(chip, &op); >>>> } >>>> >>> >> > > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
On Wed, 13 Dec 2017 21:38:44 +0100 Boris Brezillon <boris.brezillon@free-electrons.com> wrote: > On Wed, 13 Dec 2017 20:30:04 +0000 > Colin Ian King <colin.king@canonical.com> wrote: > > > On 13/12/17 20:24, Boris Brezillon wrote: > > > On Wed, 13 Dec 2017 20:17:43 +0000 > > > Colin King <colin.king@canonical.com> wrote: > > > > > >> From: Colin Ian King <colin.king@canonical.com> > > >> > > >> The check of len being zero is redundant as it has already been > > >> sanity checked for this value at the start of the function. Hence > > >> it is impossible for this test to be true and so the redundant > > >> code can be removed. > > > > > > Nope, it's not the same test, the initial test is > > > > > > if (len && !buf) > > > > Ah, the current tip from linux-next has: > > > > 1912 if (!len || !buf) > > 1913 return -EINVAL; > > > > ..so I guess that's why it got picked up by static analysis. > > Hm, that's weird, that's not what I see [1] in linux-next. This being said, the test in nand_readid_op() is wrong [1], so maybe this was the thing you were trying to fix. No need to send a new patch, I'll squash the fix in the commit introducing the function. Thanks, Boris [1]http://code.bulix.org/kxivhd-240572
On Wed, 13 Dec 2017 20:44:45 +0000 Colin Ian King <colin.king@canonical.com> wrote: > On 13/12/17 20:38, Boris Brezillon wrote: > > On Wed, 13 Dec 2017 20:30:04 +0000 > > Colin Ian King <colin.king@canonical.com> wrote: > > > >> On 13/12/17 20:24, Boris Brezillon wrote: > >>> On Wed, 13 Dec 2017 20:17:43 +0000 > >>> Colin King <colin.king@canonical.com> wrote: > >>> > >>>> From: Colin Ian King <colin.king@canonical.com> > >>>> > >>>> The check of len being zero is redundant as it has already been > >>>> sanity checked for this value at the start of the function. Hence > >>>> it is impossible for this test to be true and so the redundant > >>>> code can be removed. > >>> > >>> Nope, it's not the same test, the initial test is > >>> > >>> if (len && !buf) > >> > >> Ah, the current tip from linux-next has: > >> > >> 1912 if (!len || !buf) > >> 1913 return -EINVAL; > >> > >> ..so I guess that's why it got picked up by static analysis. > > > > Hm, that's weird, that's not what I see [1] in linux-next. > > I see my mistake, I fixed the *wrong* function, I'll send a v2. Doh. Yep, just noticed that too. No need to send a patch though.
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c index afd5e18db81c..9daaa23db943 100644 --- a/drivers/mtd/nand/nand_base.c +++ b/drivers/mtd/nand/nand_base.c @@ -1507,10 +1507,6 @@ static int nand_read_param_page_op(struct nand_chip *chip, u8 page, void *buf, }; struct nand_operation op = NAND_OPERATION(instrs); - /* Drop the DATA_IN instruction if len is set to 0. */ - if (!len) - op.ninstrs--; - return nand_exec_op(chip, &op); }