FUSE fseek unexpected behaviour with direct_io

I'm trying to write a FUSE filesystem that presents s开发者_如何学Gotreamable music as mp3 files. I don't want to start to stream the audio when just the ID3v1.1 tag is read, so I mount the filesystem with direct_io and max_readahead=0.

But when I do this (which is also what libid3tag does), I get reads of 2752 bytes with offset -2880 bytes from the end:

char tmp[255];
FILE* f = fopen("foo.mp3", "r");
fseek(f, -128, SEEK_END);
fread(tmp, 1, 10, f);

Why is this? I expect to get a call to read with an offset exactly 128 bytes from the end with size 10..

The amount of bytes read seems to vary somewhat.

I've had similar issue and filed an issue with s3fs. Checkout issue : http://code.google.com/p/s3fs/issues/detail?can=2&q=&colspec=ID%20Type%20Status%20Priority%20Milestone%20Owner%20Summary&groupby=&sort=&id=241

additionally, checkout line 1611 in the s3fs.cpp:

http://code.google.com/p/s3fs/source/browse/trunk/src/s3fs.cpp?r=316

 // error check this

 // fseek (pSourceFile , 0 , SEEK_END);