Vladislav Bolkhovitin wrote:
[EMAIL PROTECTED] wrote:
This is an updated version of [PATCH] drivers/infiniband/ulp/srpt: Fix
target data corruption
It was pointed out to me that the code to round up to a power of 2 was
not as clean as it should be, plus I extracted two unrelated patches and
submitted them separately.
=====================================================================
Change the local buffer allocator to use a spin-lock protected linked
list instead of an array of atomic_t used/free variables. The
atomic_t
code was open to a multi-thread race between test and set. This has
been observed with the result that the same data buffer was used for
more than one SCSI operation, either writing the wrong data to the
disk
or sending the wrong data to the initiator.
I, as a main SCST developer and implementor, would suggest to completely
remove internal memory management from the SRPT driver and use SCST
memory management instead. It will provide the following advantages:
1. Simplify SRPT driver and completely remove such kind of bugs.
2. Make SRPT target driver compatible with scst_user module, i.e. will
allow to use SRPT target driver with backstorage devices, implemented in
user space. Usual example of such devices is a VTL (Virtual Tape Library).
3. (Most likely, since I'm not too familiar with SRPT drivers internals,
but for me it looks like so) Allow SRPT driver to reliably work with
many outstanding commands with big data transfer sizes (>=1MB)
4. Might improve performance by caching and reusing already allocated
and "iomaped" to Infiniband hardware SG vectors. Vu knows the details,
we discussed them with him. It will require some minor SCST
modifications (extending its interface with target drivers), but I'm
willing to make them if somebody ask for it.
Oops, I forgot to mention, probably, the most important advantage:
5. Make SRPT target driver compatible with the upcoming zero-copy cache
usage, where the system cache will be used directly without the extra copy.
Vlad
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