RE: [Filesystem-dev] CR: Error handler for filesystem exception due to usb disk unplug

　　Hi Eric:
　　Agree with you.
　　And I'd like RealN assign one dev to fix it.
　　Thanks
　　
　　
　　>-----Original Message-----
　　>From: Eric Hyche [mailto:[email protected]]
　　>Sent: 2008年7月18日 0:30
　　>To: Zhao, Halley; [email protected];
　　>[email protected]
　　>Cc: [email protected];
　　>[email protected]
　　>Subject: RE: [Filesystem-dev] CR: Error handler for filesystem exception
　　>due to usb disk unplug
　　>
　　>
　　>Halley,
　　>
　　>Actually I think we should fix bug 8471 at a different level. I noticed that
　　>on Mac OSX, we do a check in MemoryMapDataFile::Bind()
　　>to check if the disk is ejectable and if it is, we disable memory-mapped
　　>I/O:
　　>
　　>    // if a windows share (smb) is shut down remotely then if
　　>    // we're memory-mapping we crash. This happened with the
　　>    // windows implementation of MemoryMapDataFile ages ago,
　　>    // and I'm pulling over their solution which is to ensure
　　>    // that memory mapping does not happen unless the disk is
　　>    // local AND non-ejectable.
　　>    if (!CHXFileSpecUtils::IsDiskLocal(dirSpec) ||
　　>CHXFileSpecUtils::IsDiskEjectable(dirSpec))
　　>    {
　　>        bMemMappingOK = false;
　　>    }
　　>
　　>Seems like we could do something similar on Linux. Unfortunately,
　　>CHXFileSpecUtils::IsDiskEjectable() currently always returns FALSE
　　>on Unix. I think if we added a similar check for IsDiskEjectable() and
　　>actually implemented IsDiskEjectable() on Unix, then what
　　>would happen would be that memory-mapped I/O would be disabled for USB disks.
　　>
　　>I believe one of our devs has verified that if memory-mapped I/O is disabled,
　　>then this solves the crash in 8471. But I think he was
　　>just testing this by hard-coding it to disable memory-mapped I/O. I think
　　>what I described above is the proper way to disable
　　>memory-mapped I/O for USB disks.
　　>
　　>Halley, do you want to make this change, or you do want to have one of our
　　>devs do it?
　　>
　　>Eric
　　>
　　>=======================================
　　>Eric Hyche ([email protected])
　　>Senior Technical Lead
　　>RealNetworks, Inc.
　　>
　　>
　　>>-----Original Message-----
　　>>From: [email protected]
　　>[mailto:[email protected]] On
　　>>Behalf Of Zhao, Halley
　　>>Sent: Thursday, July 17, 2008 4:58 AM
　　>>To: [email protected]; [email protected]
　　>>Cc: [email protected];
　　>[email protected]
　　>>Subject: [Filesystem-dev] CR: Error handler for filesystem exception due
　　>to usb disk unplug
　　>>
　　>>    I'm not familiar with file system plugin, please kindly review the
　　>patch and give your suggestion.
　　>>
　　>>    Great thanks.
　　>>
　　>>
　　>>
　　>>Synopsis:
　　>>
　　>>    The patch fix bug #8471: Device hang up after play music from USB then
　　>plug out and plug in the
　　>>USB.
　　>>
　　>>    I added error handle for usb disk unplug exception.
　　>>
　　>>
　　>>
　　>>Overview:
　　>>
　　>>  　Memory map is used in helix plugin for file io, In GetBlock() of
　　>common/fileio/mmapmgr.cpp,
　　>>
　　>>the pBuffer address is calculated from the memory page information. it may
　　>be invalid due to the
　　>>device being removed;
　　>>
　　>>then when there is a memcpy() in the future, it will crash the engine.
　　>>
　　>>　　On Windows system, it tests IsBadReadPtr()to catch the exception as
　　>early as possible.
　　>>
　　>>But there is no such check (error handle) for Linux platform. I added a
　　>function to act as
　　>>IsBadReadPtr() to catch the exception.
　　>>
　　>>
　　>>
　　>>    After memory map exception (MMAP_EOF_EXCEPTION) occurred, the Read()
　　>function in
　　>>common/fileio/platform/unix/mmapdatf.cpp
　　>>
　　>>will regress to normal_read. and it will consume some data which has been
　　>mapped in memory.
　　>>
　　>>then in CheckForCorruptFile() of filesystem/local/full/smplfsys.cpp, we
　　>should try to consider this
　　>>situation.
　　>>
　　>>and in this scenario file size (m_ulSize) isn't initialized. We could
　　>determine it is a corrupt file
　　>>depends on m_ulSize equal to 0.
　　>>
　　>>
　　>>
　　>>Files Added:
　　>>
　　>>       No file added
　　>>
　　>>Files Modified:
　　>>
　　>>    common/fileio/mmapmgr.cpp
　　>>
　　>>        add function _IsBadReadPtr() to detect whether the file is
　　>available, and try to catch the
　　>>exception due to device removed.
　　>>
　　>>    filesystem/local/full/smplfsys.cpp
　　>>
　　>>        file size (m_ulSize) equal to 0 means a corrupt file.
　　>>
　　>>
　　>>
　　>>Image Size and Heap Use impact (Client -Only):
　　>>
　　>>    little
　　>>
　　>>Platforms and Profiles Affected:
　　>>
　　>>    platform:   linux-2.2-libc6-gcc32-i586
　　>>
　　>>    profile:    helix-client-all-defines
　　>>
　　>>
　　>>
　　>>Distribution Libraries Affected:
　　>>
　　>>    <smplfsys.so>
　　>>
　　>>Distribution library impact and planned action:
　　>>
　　>>    <None>
　　>>
　　>>Platforms and Profiles Build Verified:
　　>>
　　>>    Set BIF branch  -> hxclient_3_1_0_atlas_restricted
　　>>
　　>>    Set Target(s)   -> player_mid_all_installers (or splay)
　　>>
　　>>    Set Profile     -> helix-client-all-defines
　　>>
　　>>    System ID       -> linux-2.2-libc6-gcc32-i586
　　>>
　　>>Branch:
　　>>
　　>>    HEAD
　　>>
　　>>Copyright assignment: <MUST be one of the following statements >
　　>>
　　>>   2.      Intel has signed and delivered a Joint Copyright Assignment
　　>>
　　>>           to RealNetworks, and received acknowledgment that the
　　>>
　　>>           agreement was received.
　　>>
　　>>Files Attached:
　　>>
　　>>    common-fileio-mmapmgr.cpp.diff.txt
　　>>
　　>>    filesystem-local-smplsys.cpp.diff.txt
　　>>
　　>>
　　>>
　　>>ZHAO, Halley (Aihua)
　　>>
　　>>Email: [email protected] <mailto:[email protected]>
　　>>
　　>>Tel: +86(21)61166476
　　>>
　　>>iNet: 8821-6476
　　>>
　　>>SSG/OTC/UMD
　　>>
　　>>
　　>
　　

_______________________________________________
Helix-client-dev mailing list
[email protected]
http://lists.helixcommunity.org/mailman/listinfo/helix-client-dev