Hi,
I''m having a problem with a simple sanity check performed by
''iozone -a''.
Basically, iozone create a file with a permission value of 0 and then it tries
to truncate it:
1) fd = open("file", O_WRONLY|O_CREAT, 0)
2) ftruncate(fd, 0)
In zfs-fuse, the ftruncate() call ends up calling zfs_setattr() with AT_SIZE
set in the attribute mask.
The problem is that one of the first things zfs_setattr() does is validate the
permissions (by calling zfs_zaccess()), which fails since the file owner
doesn''t have write permission.
What am I doing wrong here? iozone seems to work in Solaris.
Thanks.
Ricardo Correia wrote:> Hi, > > I''m having a problem with a simple sanity check performed by ''iozone -a''. > > Basically, iozone create a file with a permission value of 0 and then it tries > to truncate it: > > 1) fd = open("file", O_WRONLY|O_CREAT, 0) > 2) ftruncate(fd, 0) > > In zfs-fuse, the ftruncate() call ends up calling zfs_setattr() with AT_SIZE > set in the attribute mask. > > The problem is that one of the first things zfs_setattr() does is validate the > permissions (by calling zfs_zaccess()), which fails since the file owner > doesn''t have write permission. > > What am I doing wrong here? iozone seems to work in Solaris.ftruncate/truncate on Solaris are implemented via the F_FREESP command in fcntl(2). This ultimately calls VOP_SPACE() which doesn''t need to do any access checks since the file was already opened with the necessary "write" permission. http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/syscall/fcntl.c#546 Do any ACL check in this situation is not going to work, unless the user has appropriate privileges to override the permissions on the ACL. -Mark
On Sunday 21 January 2007 21:17, Mark Shellenbaum wrote:> ftruncate/truncate on Solaris are implemented via the F_FREESP command > in fcntl(2). This ultimately calls VOP_SPACE() which doesn''t need to do > any access checks since the file was already opened with the necessary > "write" permission.Hi Mark :) That would explain it. For some reason, I was convinced ftruncate() in userspace would lead to a VOP_SETATTR() in the kernel. That also explains why I wasn''t getting DTrace to trace zfs_setattr(), which was starting to get a little frustrating :) Thanks!