Hi All,
My system configuration is :
Arch : ppc7400
kernel : 2.6.21
Memory : 512MB.
Filesystem : XFS
I am facing a strange problem !
When i do a read operation on a large file, i am not getting the
expected data (ie., it reads wrong data).
I have written a simple read & write program, where it does the
following :
1.allocate a buffer of 314MB
2.memset it to '5'
3.write this buffer to a file
4.fsync the file
5.close the file
6.open the same file
7.read the contents in chunksize of 4k into a buffer.
8.check the contents for '5'
Here i am supposed to get only '5's, but i get some different value
after some reads.
The interesting thing here is : If i open the file with O_DIRECT, i
don't see such inconsistency.
Due to this inconsistency, i am not able to untar a large file (600MB)
properly. In the middle of untarring i get "Invalid headers". Copy
operations are also not happening properly, get "Structure needs
cleanining" in the middle of copy. Even the compare on two same files
shows me differences.
I guess all the above inconsistency is due to the "buffered read path".
Some thing goes wrong in the flow of buffered reads.
I have checked the buffer inside the "do_generic_mapping_read" function
(ie., before the copy_to_user ), even here there is inconsistency.
I checked the memory with memtest, and harddisk with smartmon tools,
found no errors here. Also same problem is reproduced on different m/c's
with similar configuration.
Is this a bug in kernel-2.6.21-PPC?
Please help me on finding out the problem.
Thanks
Ashok
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