I’m trying to switch from using sycall/kernel-driver to direct pvfs_*() functions. A major issue is that pvfs_getxattr() returns a length 1 byte longer than syscalls, as shown:
svy@papp1:~$ sudo attr -l /srv/data/cyphre-v2/user0 Attribute "cyphre.owner" has a 6 byte value for /srv/data/cyphre-v2/user0 svy@papp1:~$ sudo ./attr-test /srv/data/cyphre-v2/user0 user.cyphre.owner is 7 bytes Note that 6 is the correct answer. It’s the length I set with setxattr(). The second program was a quick one I write using pvfs_getxattr() where as the first one is using the attr program, so it uses getxattr() syscall directly, and goes through the kernel driver. If I do something like: len = pvfs_getxattr(path, key, NULL, 0); len—; // True length buf = malloc(len); len = pvfs_getxattr(path, key, buf, len); I get data that is, technically, the right length, but truncated by one byte (last byte is ‘\0’). My assumption (without digging too deep) is that the pvfs function adds an extra byte to null terminate the buffer, but it definitely shouldn’t do this (keys, sure, but not values). Either way, this makes the pvfs wrapper incompatible with the posix functions. —— Ben Collins Cyphre Champion —————————————— VP of Engineering Servergy, Inc.
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