Re: [PATCH] udf: fix the problem that the disc content is not displayed

2021-01-14 Thread Jan Kara 
On Thu 14-01-21 21:26:15, lianzhi chang wrote:
> When the capacity of the disc is too large (assuming the 4.7G
> specification), the disc (UDF file system) will be burned
> multiple times in the windows (Multisession Usage). When the
> remaining capacity of the CD is less than 300M (estimated
> value, for reference only), open the CD in the Linux system,
> the content of the CD is displayed as blank (the kernel will
> say "No VRS found"). Windows can display the contents of the
> CD normally.
> Through analysis, in the "fs/udf/super.c": udf_check_vsd
> function, the actual value of VSD_MAX_SECTOR_OFFSET may
> be much larger than 0x80. According to the current code
> logic, it is found that the type of sbi->s_session is "__s32",
>  when the remaining capacity of the disc is less than 300M
> (take a set of test values: sector=3154903040,
> sbi->s_session=1540464, sb->s_blocksize_bits=11 ), the
> calculation result of "sbi->s_session << sb->s_blocksize_bits"
>  will overflow. Therefore, it is necessary to convert the
> type of s_session to "loff_t" (when udf_check_vsd starts,
> assign a value to _sector, which is also converted in this
> way), so that the result will not overflow, and then the
> content of the disc can be displayed normally.
> 
> Signed-off-by: lianzhi chang 

There was no need to resend the patch (I've fixed up the problem locally -
it was easy enough) but thanks anyway :).

Honza

> ---
>  fs/udf/super.c | 7 ---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/udf/super.c b/fs/udf/super.c
> index 5bef3a68395d..f2ff98f393fb 100644
> --- a/fs/udf/super.c
> +++ b/fs/udf/super.c
> @@ -705,6 +705,7 @@ static int udf_check_vsd(struct super_block *sb)
>   struct buffer_head *bh = NULL;
>   int nsr = 0;
>   struct udf_sb_info *sbi;
> + loff_t sector_offset;
>  
>   sbi = UDF_SB(sb);
>   if (sb->s_blocksize < sizeof(struct volStructDesc))
> @@ -712,7 +713,8 @@ static int udf_check_vsd(struct super_block *sb)
>   else
>   sectorsize = sb->s_blocksize;
>  
> - sector += (((loff_t)sbi->s_session) << sb->s_blocksize_bits);
> + sector_offset = (loff_t)sbi->s_session << sb->s_blocksize_bits;
> + sector += sector_offset;
>  
>   udf_debug("Starting at sector %u (%lu byte sectors)\n",
> (unsigned int)(sector >> sb->s_blocksize_bits),
> @@ -757,8 +759,7 @@ static int udf_check_vsd(struct super_block *sb)
>  
>   if (nsr > 0)
>   return 1;
> - else if (!bh && sector - (sbi->s_session << sb->s_blocksize_bits) ==
> - VSD_FIRST_SECTOR_OFFSET)
> + else if (!bh && sector - sector_offset == VSD_FIRST_SECTOR_OFFSET)
>   return -1;
>   else
>   return 0;
> -- 
> 2.20.1
> 
> 
> 
-- 
Jan Kara 
SUSE Labs, CR

[PATCH] udf: fix the problem that the disc content is not displayed

2021-01-14 Thread lianzhi chang 
When the capacity of the disc is too large (assuming the 4.7G
specification), the disc (UDF file system) will be burned
multiple times in the windows (Multisession Usage). When the
remaining capacity of the CD is less than 300M (estimated
value, for reference only), open the CD in the Linux system,
the content of the CD is displayed as blank (the kernel will
say "No VRS found"). Windows can display the contents of the
CD normally.
Through analysis, in the "fs/udf/super.c": udf_check_vsd
function, the actual value of VSD_MAX_SECTOR_OFFSET may
be much larger than 0x80. According to the current code
logic, it is found that the type of sbi->s_session is "__s32",
 when the remaining capacity of the disc is less than 300M
(take a set of test values: sector=3154903040,
sbi->s_session=1540464, sb->s_blocksize_bits=11 ), the
calculation result of "sbi->s_session << sb->s_blocksize_bits"
 will overflow. Therefore, it is necessary to convert the
type of s_session to "loff_t" (when udf_check_vsd starts,
assign a value to _sector, which is also converted in this
way), so that the result will not overflow, and then the
content of the disc can be displayed normally.

Signed-off-by: lianzhi chang 
---
 fs/udf/super.c | 7 ---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 5bef3a68395d..f2ff98f393fb 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -705,6 +705,7 @@ static int udf_check_vsd(struct super_block *sb)
struct buffer_head *bh = NULL;
int nsr = 0;
struct udf_sb_info *sbi;
+   loff_t sector_offset;
 
sbi = UDF_SB(sb);
if (sb->s_blocksize < sizeof(struct volStructDesc))
@@ -712,7 +713,8 @@ static int udf_check_vsd(struct super_block *sb)
else
sectorsize = sb->s_blocksize;
 
-   sector += (((loff_t)sbi->s_session) << sb->s_blocksize_bits);
+   sector_offset = (loff_t)sbi->s_session << sb->s_blocksize_bits;
+   sector += sector_offset;
 
udf_debug("Starting at sector %u (%lu byte sectors)\n",
  (unsigned int)(sector >> sb->s_blocksize_bits),
@@ -757,8 +759,7 @@ static int udf_check_vsd(struct super_block *sb)
 
if (nsr > 0)
return 1;
-   else if (!bh && sector - (sbi->s_session << sb->s_blocksize_bits) ==
-   VSD_FIRST_SECTOR_OFFSET)
+   else if (!bh && sector - sector_offset == VSD_FIRST_SECTOR_OFFSET)
return -1;
else
return 0;
-- 
2.20.1

Re: [PATCH] udf: fix the problem that the disc content is not displayed【Suspected phishing email, please pay attention to password security】

2021-01-14 Thread changlian...@uniontech.com 

>There's imbalanced parentheses here, I'll fix it up on commit. Otherwise
>the fix looks good to me. Thanks!

>--
>Jan Kara 
>SUSE Labs, CR

sorry,I will resubmit it again！thank you very much!

Re: [PATCH] udf: fix the problem that the disc content is not displayed

2021-01-14 Thread kernel test robot 
Hi lianzhi,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.11-rc3 next-20210114]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:
https://github.com/0day-ci/linux/commits/lianzhi-chang/udf-fix-the-problem-that-the-disc-content-is-not-displayed/20210114-161012
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 
65f0d2414b7079556fbbcc070b3d1c9f9587606d
config: mips-randconfig-r026-20210114 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 
6077d55381a6aa3e947ef7abdc36a7515c598c8a)
reproduce (this is a W=1 build):
wget 
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O 
~/bin/make.cross
chmod +x ~/bin/make.cross
# install mips cross compiling tool for clang build
# apt-get install binutils-mips-linux-gnu
# 
https://github.com/0day-ci/linux/commit/76a7c356fa5bfe473a3d7c15bda5922c902a33f7
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review 
lianzhi-chang/udf-fix-the-problem-that-the-disc-content-is-not-displayed/20210114-161012
git checkout 76a7c356fa5bfe473a3d7c15bda5922c902a33f7
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot 

All errors (new ones prefixed by >>):

   In file included from include/linux/atomic.h:7:
   arch/mips/include/asm/atomic.h:257:1: warning: converting the result of '<<' 
to a boolean always evaluates to true [-Wtautological-constant-compare]
   ATOMIC_SIP_OP(atomic, int, subu, ll, sc)
   ^
   arch/mips/include/asm/atomic.h:251:7: note: expanded from macro 
'ATOMIC_SIP_OP'
   if (!__SYNC_loongson3_war)  \
^
   arch/mips/include/asm/sync.h:147:34: note: expanded from macro 
'__SYNC_loongson3_war'
   # define __SYNC_loongson3_war   (1 << 31)
  ^
   In file included from fs/udf/super.c:41:
   In file included from fs/udf/udfdecl.h:10:
   In file included from include/linux/fs.h:6:
   In file included from include/linux/wait_bit.h:8:
   In file included from include/linux/wait.h:9:
   In file included from include/linux/spinlock.h:51:
   In file included from include/linux/preempt.h:78:
   In file included from ./arch/mips/include/generated/asm/preempt.h:1:
   In file included from include/asm-generic/preempt.h:5:
   In file included from include/linux/thread_info.h:56:
   In file included from arch/mips/include/asm/thread_info.h:16:
   In file included from arch/mips/include/asm/processor.h:14:
   In file included from include/linux/atomic.h:7:
   arch/mips/include/asm/atomic.h:261:1: warning: converting the result of '<<' 
to a boolean always evaluates to true [-Wtautological-constant-compare]
   ATOMIC_SIP_OP(atomic64, s64, dsubu, lld, scd)
   ^
   arch/mips/include/asm/atomic.h:251:7: note: expanded from macro 
'ATOMIC_SIP_OP'
   if (!__SYNC_loongson3_war)  \
^
   arch/mips/include/asm/sync.h:147:34: note: expanded from macro 
'__SYNC_loongson3_war'
   # define __SYNC_loongson3_war   (1 << 31)
  ^
   In file included from fs/udf/super.c:41:
   In file included from fs/udf/udfdecl.h:10:
   In file included from include/linux/fs.h:6:
   In file included from include/linux/wait_bit.h:8:
   In file included from include/linux/wait.h:9:
   In file included from include/linux/spinlock.h:59:
   In file included from include/linux/lockdep.h:14:
   In file included from include/linux/smp.h:15:
   In file included from include/linux/smp_types.h:5:
   include/linux/llist.h:237:9: warning: converting the result of '<<' to a 
boolean always evaluates to true [-Wtautological-constant-compare]
   return xchg(>first, NULL);
  ^
   arch/mips/include/asm/cmpxchg.h:102:7: note: expanded from macro 'xchg'
   if (!__SYNC_loongson3_war)  \
^
   arch/mips/include/asm/sync.h:147:34: note: expanded from macro 
'__SYNC_loongson3_war'
   # define __SYNC_loongson3_war   (1 << 31)
  ^
   In file included from fs/udf/super.c:41:
   In file included from fs/udf/udfdecl.h:10:
   In file included from include/linux/fs.h:6:
   In file included from include/linux/wait_bit.h:8:
   In file included from include/linux/wait.h:9:
   In file included from include/linux/spinlock.h:59:
   In file included from include/linux/lockdep.h:27:
   include/linux/debug_locks.h:17:9: warning: converting the result of '<<' to 
a boolean always

Re: [PATCH] udf: fix the problem that the disc content is not displayed

2021-01-14 Thread Jan Kara 
On Thu 14-01-21 15:57:41, lianzhi chang wrote:
> When the capacity of the disc is too large (assuming the 4.7G
> specification), the disc (UDF file system) will be burned
> multiple times in the windows (Multisession Usage). When the
> remaining capacity of the CD is less than 300M (estimated
> value, for reference only), open the CD in the Linux system,
> the content of the CD is displayed as blank (the kernel will
> say "No VRS found"). Windows can display the contents of the
> CD normally.
> Through analysis, in the "fs/udf/super.c": udf_check_vsd
> function, the actual value of VSD_MAX_SECTOR_OFFSET may
> be much larger than 0x80. According to the current code
> logic, it is found that the type of sbi->s_session is "__s32",
>  when the remaining capacity of the disc is less than 300M
> (take a set of test values: sector=3154903040,
> sbi->s_session=1540464, sb->s_blocksize_bits=11 ), the
> calculation result of "sbi->s_session << sb->s_blocksize_bits"
>  will overflow. Therefore, it is necessary to convert the
> type of s_session to "loff_t" (when udf_check_vsd starts,
> assign a value to _sector, which is also converted in this
> way), so that the result will not overflow, and then the
> content of the disc can be displayed normally.
> 
> Signed-off-by: lianzhi chang 
> ---
>  fs/udf/super.c | 7 ---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/udf/super.c b/fs/udf/super.c
> index 5bef3a68395d..f2ff98f393fb 100644
> --- a/fs/udf/super.c
> +++ b/fs/udf/super.c
> @@ -705,6 +705,7 @@ static int udf_check_vsd(struct super_block *sb)
>   struct buffer_head *bh = NULL;
>   int nsr = 0;
>   struct udf_sb_info *sbi;
> + loff_t sector_offset;
>  
>   sbi = UDF_SB(sb);
>   if (sb->s_blocksize < sizeof(struct volStructDesc))
> @@ -712,7 +713,8 @@ static int udf_check_vsd(struct super_block *sb)
>   else
>   sectorsize = sb->s_blocksize;
>  
> - sector += (((loff_t)sbi->s_session) << sb->s_blocksize_bits);
> + sector_offset = (loff_t)sbi->s_session << sb->s_blocksize_bits);

There's imbalanced parentheses here, I'll fix it up on commit. Otherwise
the fix looks good to me. Thanks!

Honza

> + sector += sector_offset;
>  
>   udf_debug("Starting at sector %u (%lu byte sectors)\n",
> (unsigned int)(sector >> sb->s_blocksize_bits),
> @@ -757,8 +759,7 @@ static int udf_check_vsd(struct super_block *sb)
>  
>   if (nsr > 0)
>   return 1;
> - else if (!bh && sector - (sbi->s_session << sb->s_blocksize_bits) ==
> - VSD_FIRST_SECTOR_OFFSET)
> + else if (!bh && sector - sector_offset == VSD_FIRST_SECTOR_OFFSET)
>   return -1;
>   else
>   return 0;
> -- 
> 2.20.1
> 
> 
> 
-- 
Jan Kara 
SUSE Labs, CR

[PATCH] udf: fix the problem that the disc content is not displayed

2021-01-14 Thread lianzhi chang 
When the capacity of the disc is too large (assuming the 4.7G
specification), the disc (UDF file system) will be burned
multiple times in the windows (Multisession Usage). When the
remaining capacity of the CD is less than 300M (estimated
value, for reference only), open the CD in the Linux system,
the content of the CD is displayed as blank (the kernel will
say "No VRS found"). Windows can display the contents of the
CD normally.
Through analysis, in the "fs/udf/super.c": udf_check_vsd
function, the actual value of VSD_MAX_SECTOR_OFFSET may
be much larger than 0x80. According to the current code
logic, it is found that the type of sbi->s_session is "__s32",
 when the remaining capacity of the disc is less than 300M
(take a set of test values: sector=3154903040,
sbi->s_session=1540464, sb->s_blocksize_bits=11 ), the
calculation result of "sbi->s_session << sb->s_blocksize_bits"
 will overflow. Therefore, it is necessary to convert the
type of s_session to "loff_t" (when udf_check_vsd starts,
assign a value to _sector, which is also converted in this
way), so that the result will not overflow, and then the
content of the disc can be displayed normally.

Signed-off-by: lianzhi chang 
---
 fs/udf/super.c | 7 ---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 5bef3a68395d..f2ff98f393fb 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -705,6 +705,7 @@ static int udf_check_vsd(struct super_block *sb)
struct buffer_head *bh = NULL;
int nsr = 0;
struct udf_sb_info *sbi;
+   loff_t sector_offset;
 
sbi = UDF_SB(sb);
if (sb->s_blocksize < sizeof(struct volStructDesc))
@@ -712,7 +713,8 @@ static int udf_check_vsd(struct super_block *sb)
else
sectorsize = sb->s_blocksize;
 
-   sector += (((loff_t)sbi->s_session) << sb->s_blocksize_bits);
+   sector_offset = (loff_t)sbi->s_session << sb->s_blocksize_bits);
+   sector += sector_offset;
 
udf_debug("Starting at sector %u (%lu byte sectors)\n",
  (unsigned int)(sector >> sb->s_blocksize_bits),
@@ -757,8 +759,7 @@ static int udf_check_vsd(struct super_block *sb)
 
if (nsr > 0)
return 1;
-   else if (!bh && sector - (sbi->s_session << sb->s_blocksize_bits) ==
-   VSD_FIRST_SECTOR_OFFSET)
+   else if (!bh && sector - sector_offset == VSD_FIRST_SECTOR_OFFSET)
return -1;
else
return 0;
-- 
2.20.1

Re: [PATCH] udf: fix the problem that the disc content is not displayed

2021-01-13 Thread changlian...@uniontech.com 
On 2021-01-13 20:51, 常廉志 wrote:

>> On 2021-01-11 23:53, lianzhi chang wrote:
>>
 When the capacity of the disc is too large (assuming the 4.7G
 specification), the disc (UDF file system) will be burned
 multiple times in the windows (Multisession Usage). When the
 remaining capacity of the CD is less than 300M (estimated
 value, for reference only), open the CD in the Linux system,
 the content of the CD is displayed as blank (the kernel will
 say "No VRS found"). Windows can display the contents of the
 CD normally.
 Through analysis, in the "fs/udf/super.c": udf_check_vsd
 function, the actual value of VSD_MAX_SECTOR_OFFSET may
 be much larger than 0x80. According to the current code
>>> l>ogic, it is found that the type of sbi->s_session is "__s32",
 when the remaining capacity of the disc is less than 300M
 (take a set of test values: sector=3154903040,
 sbi->s_session=1540464, sb->s_blocksize_bits=11 ), the
 calculation result of "sbi->s_session << sb->s_blocksize_bits"
 will overflow. Therefore, it is necessary to convert the
 type of s_session to "loff_t" (when udf_check_vsd starts,
 assign a value to _sector, which is also converted in this
 way), so that the result will not overflow, and then the
 content of the disc can be displayed normally.

>>> Signed-off-by: lianzhi chang 
 ---
 fs/udf/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

 diff --git a/fs/udf/super.c b/fs/udf/super.c
 index 5bef3a68395d..6c3069cd1321 100644
 --- a/fs/udf/super.c
 +++ b/fs/udf/super.c
 @@ -757,7 +757,7 @@ static int udf_check_vsd(struct super_block *sb)

 if (nsr > 0)
 return 1;
 - else if (!bh && sector - (sbi->s_session << sb->s_blocksize_bits)
 ==
 + else if (!bh && sector - ((loff_t)sbi->s_session <<
 sb->s_blocksize_bits) ==
 VSD_FIRST_SECTOR_OFFSET)
 return -1;
 else
>>>
>>>
>>> Looks good. Perhaps consider factoring out the conversion (which also
>>> occurs
>>> earlier in the function) so that the complexity of this "else if" can
>>> be
>>> reduced?
>>>
>>
>>> Reviewed-by: Steven J. Magnani 
>>
>> Thank you very much! So, which one of the following methods do you
>> think is better:
>>
>> (1) Change the type of s_session in struct udf_sb_info to __s64. If you
>> modify this way, it may involve some memory copy problems of the
>> structure, and there are more modifications.
>>
>> (2) Definition: loff_t sector_offset=sbi->s_session <<
>> sb->s_blocksize_bits, and then put sector_offset into the "else if"
>> statement.
>>
>> (3) Or is there any other better way?

>I had #2 in mind.
>
>  Steven J. Magnani   "I claim this network for MARS!

Thank you very much for your suggestion, I will submit a new patch

Re: [PATCH] udf: fix the problem that the disc content is not displayed

2021-01-13 Thread Steve Magnani 

On 2021-01-13 20:51, 常廉志 wrote:


On 2021-01-11 23:53, lianzhi chang wrote:


When the capacity of the disc is too large (assuming the 4.7G
specification), the disc (UDF file system) will be burned
multiple times in the windows (Multisession Usage). When the
remaining capacity of the CD is less than 300M (estimated
value, for reference only), open the CD in the Linux system,
the content of the CD is displayed as blank (the kernel will
say "No VRS found"). Windows can display the contents of the
CD normally.
Through analysis, in the "fs/udf/super.c": udf_check_vsd
function, the actual value of VSD_MAX_SECTOR_OFFSET may
be much larger than 0x80. According to the current code

l>ogic, it is found that the type of sbi->s_session is "__s32",

when the remaining capacity of the disc is less than 300M
(take a set of test values: sector=3154903040,
sbi->s_session=1540464, sb->s_blocksize_bits=11 ), the
calculation result of "sbi->s_session << sb->s_blocksize_bits"
will overflow. Therefore, it is necessary to convert the
type of s_session to "loff_t" (when udf_check_vsd starts,
assign a value to _sector, which is also converted in this
way), so that the result will not overflow, and then the
content of the disc can be displayed normally.

Signed-off-by: lianzhi chang 
---
fs/udf/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 5bef3a68395d..6c3069cd1321 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -757,7 +757,7 @@ static int udf_check_vsd(struct super_block *sb)

if (nsr > 0)
return 1;
- else if (!bh && sector - (sbi->s_session << sb->s_blocksize_bits) 
==

+ else if (!bh && sector - ((loff_t)sbi->s_session <<
sb->s_blocksize_bits) ==
VSD_FIRST_SECTOR_OFFSET)
return -1;
else



Looks good. Perhaps consider factoring out the conversion (which also
occurs
earlier in the function) so that the complexity of this "else if" can 
be

reduced?




Reviewed-by: Steven J. Magnani 


Thank you very much! So, which one of the following methods do you 
think is better:


(1) Change the type of s_session in struct udf_sb_info to __s64. If you 
modify this way, it may involve some memory copy problems of the 
structure, and there are more modifications.


(2) Definition: loff_t sector_offset=sbi->s_session << 
sb->s_blocksize_bits, and then put sector_offset into the "else if" 
statement.


(3) Or is there any other better way?


I had #2 in mind.

 Steven J. Magnani   "I claim this network for MARS!
  Earthling, return my space modulator!"
 #include

Re: [PATCH] udf: fix the problem that the disc content is not displayed

2021-01-13 Thread Steve Magnani 

On 2021-01-11 23:53, lianzhi chang wrote:

When the capacity of the disc is too large (assuming the 4.7G
specification), the disc (UDF file system) will be burned
multiple times in the windows (Multisession Usage). When the
remaining capacity of the CD is less than 300M (estimated
value, for reference only), open the CD in the Linux system,
the content of the CD is displayed as blank (the kernel will
say "No VRS found"). Windows can display the contents of the
CD normally.
Through analysis, in the "fs/udf/super.c": udf_check_vsd
function, the actual value of VSD_MAX_SECTOR_OFFSET may
be much larger than 0x80. According to the current code
logic, it is found that the type of sbi->s_session is "__s32",
 when the remaining capacity of the disc is less than 300M
(take a set of test values: sector=3154903040,
sbi->s_session=1540464, sb->s_blocksize_bits=11 ), the
calculation result of "sbi->s_session << sb->s_blocksize_bits"
 will overflow. Therefore, it is necessary to convert the
type of s_session to "loff_t" (when udf_check_vsd starts,
assign a value to _sector, which is also converted in this
way), so that the result will not overflow, and then the
content of the disc can be displayed normally.

Signed-off-by: lianzhi chang 
---
 fs/udf/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 5bef3a68395d..6c3069cd1321 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -757,7 +757,7 @@ static int udf_check_vsd(struct super_block *sb)

if (nsr > 0)
return 1;
-   else if (!bh && sector - (sbi->s_session << sb->s_blocksize_bits) ==
+	else if (!bh && sector - ((loff_t)sbi->s_session << 
sb->s_blocksize_bits) ==

VSD_FIRST_SECTOR_OFFSET)
return -1;
else



Looks good. Perhaps consider factoring out the conversion (which also 
occurs
earlier in the function) so that the complexity of this "else if" can be 
reduced?


Reviewed-by: Steven J. Magnani 

 Steven J. Magnani   "I claim this network for MARS!
  Earthling, return my space modulator!"

 #include

[PATCH] udf: fix the problem that the disc content is not displayed

2021-01-11 Thread lianzhi chang 
When the capacity of the disc is too large (assuming the 4.7G
specification), the disc (UDF file system) will be burned
multiple times in the windows (Multisession Usage). When the
remaining capacity of the CD is less than 300M (estimated
value, for reference only), open the CD in the Linux system,
the content of the CD is displayed as blank (the kernel will
say "No VRS found"). Windows can display the contents of the
CD normally.
Through analysis, in the "fs/udf/super.c": udf_check_vsd
function, the actual value of VSD_MAX_SECTOR_OFFSET may
be much larger than 0x80. According to the current code
logic, it is found that the type of sbi->s_session is "__s32",
 when the remaining capacity of the disc is less than 300M
(take a set of test values: sector=3154903040,
sbi->s_session=1540464, sb->s_blocksize_bits=11 ), the
calculation result of "sbi->s_session << sb->s_blocksize_bits"
 will overflow. Therefore, it is necessary to convert the
type of s_session to "loff_t" (when udf_check_vsd starts,
assign a value to _sector, which is also converted in this
way), so that the result will not overflow, and then the
content of the disc can be displayed normally.

Signed-off-by: lianzhi chang 
---
 fs/udf/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/udf/super.c b/fs/udf/super.c
index 5bef3a68395d..6c3069cd1321 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -757,7 +757,7 @@ static int udf_check_vsd(struct super_block *sb)
 
if (nsr > 0)
return 1;
-   else if (!bh && sector - (sbi->s_session << sb->s_blocksize_bits) ==
+   else if (!bh && sector - ((loff_t)sbi->s_session << 
sb->s_blocksize_bits) ==
VSD_FIRST_SECTOR_OFFSET)
return -1;
else
-- 
2.20.1