Messages in this thread | | | Date | Wed, 13 Jan 2021 21:21:14 -0600 | From | Steve Magnani <> | Subject | Re: [PATCH] udf: fix the problem that the disc content is not displayed |
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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 0x800000. 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 <changlianzhi@uniontech.com> >>> --- >>> 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 <magnani@xxxxxxxx> > > 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 <standard.disclaimer>
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