When running fsx (file system exerciser, from freebsd/apple -
http://www.freebsd.org/cgi/cvsweb.cgi/src/tools/regression/fsx/), we are
seeing some failures when doing truncate operations. The behaviour seems
to be:
Open a new file
Write some data
truncate the file so that it is shorter
truncate it so that it is larger - the intervening space should be all
nuls (see ftruncate manpage).
Write some data at the new end of the file, thus leaving the hole in the
middle.

fsx complains that the intervening space is not-nul.

I haven't been able to write a straight forward test case, so it is
possible that this bug is intermittent, or my interpretation of the fsx
output is wrong.

Also, the problem seems to go away if I force fsx to only truncate onto
page boundaries (multiples of 2048 bytes).

I used the following command line to trigger the failure:
 ./fsx -N 10000 /mnt/foo

I've attached the output of fsx, although the relevant parts are the top:
READ BAD DATA: offset = 0xdd7c, size = 0xd933
OFFSET  GOOD    BAD     RANGE
0x f000 0x0000  0x6c22  0x  7fc

and the bottom:
9602(130 mod 256): MAPREAD      0x2d86c thru 0x382f1    (0xaa86 bytes)
9603(131 mod 256): TRUNCATE DOWN        from 0x3c5fd to 0xb013  ******WWWW
9604(132 mod 256): WRITE        0x19606 thru 0x282e0    (0xecdb bytes)
HOLE     ***WWWW
9605(133 mod 256): WRITE        0x1d4e2 thru 0x1dfd5    (0xaf4 bytes)
9606(134 mod 256): MAPREAD      0xdd7c thru 0x1b6ae     (0xd933 bytes)
***RRRR***

This indicates that at offset 0xf000, it was expecting to read nuls
(GOOD: 0x0000), but it read non null (BAD: 0x6c22), having done a
truncate down to 0xb013,

Does anyone know about anything like this?
Andre

-- 
Bluewater Systems Ltd - ARM Technology Solutions Centre

       Andre Renaud                             Bluewater Systems Ltd
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