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#24 Patch against bug 3329249

open-fixed
my space
None
5
2012-07-10
2012-06-10
Ata E Husain
No

The issue surfaced when I attempted to use 7za to provide a VM backup solution on ESXi platform. If the VM is powered off I am able to zip the VM directory as well as all related files; but for powered ON VMs given the vmdk file is locked by hypervisor, the only solution is to first create a snapshot file and then zip up the unlocked VMDK file. Suprisigly 9.20 fails if compression option is mx=1, it fails with error E_FAIL. With no-compression operation selected the operation is a success.

The submitted patch replaces the system call for "file operation" to use C library file operation calls, that works fine. It is tested against VM of sizes as big as 100G and it works fine.

Thanks!
Ata

Discussion

  • Ata E Husain
    Ata E Husain
    2012-06-10

    • status: open --> open-fixed
     
  • Ata E Husain
    Ata E Husain
    2012-06-13

    • assigned_to: nobody --> ipavlov
     
  • my p7zip
    my p7zip
    2012-07-10

    • assigned_to: ipavlov --> myspace
     
  • my p7zip
    my p7zip
    2012-07-10

    open/close/read/write/lseek are functions which are available in old and new Unix.

    I don't know about fseeko/ftello/..
    And what about : ftruncate(fileno(_fd), pos_cur) ?

    Moreover:
    ! case CREATE_NEW : flags += "w"; break;
    ! case CREATE_ALWAYS : flags += "w"; break;
    ! case OPEN_EXISTING : break;
    ! case OPEN_ALWAYS : flags += "w"; break;
    CREATE_NEW and CREATE_ALWAYS don't have the same behaviour
    but for "fopen", you use "w" ...

    What OS is ESXi platform ? Linux ?

    I don't understand why "fopen" works and not open.
    On Unix, fopen uses open ...

    Perhaps, on your platform, you need to add a flag for "open".
    What flags were used when the open failed ?

    #ifdef O_MY_FLAG_FOR_THIS_PLATFORM
    flags |= O_MY_FLAG_FOR_THIS_PLATFORM;
    #endif

    Where O_MY_FLAG_FOR_THIS_PLATFORM makes open behave like fopen ...

     
  • Ata E Husain
    Ata E Husain
    2012-07-13

    I need to confirm this as its a long time, but the issue only came up with powerred ON VMs (snapshot file was created so data file *-flat.vmdk was freezed). IIRC, it was the issue with reading the file contents than just opening the file.

    As fread/fwrite are different from read/write system calls (I think they use bcopy() or similar call to read the data and also they are buffered in nature of there operation), thus using C system library works whereas basic system calls where failing.

    ESXi 4.1 which I used is 32 bit OS close to Linux but not compeltly a Linux OS. In my test I opened the file in RD_ONLY mode for open and "rb" for fread/fwrite.

    fseeko/ftello supports 64 bit offset handling and is better to handle large files. At first I used fseek/ftell version of calls, but it failed for VMs with disk size ~100G or so.

    So far, I was not able to see any issues replacing system calls with C library calls, given C library calls are reliable and widely used. Please share if you forsee any concerns.

    Thanks!
    Ata