On Thursday 25 February 2010 3:28:50 pm Juergen Lock wrote:
> On Tue, Feb 23, 2010 at 10:50:10PM +0100, Juergen Lock wrote:
> > Hi!
> >
> > Before this gets buried on -hackers in another thead... :)
> >
> > I now have disks appear as block devices for Linux processes (there
> > already was commented out code for that in linux_stats.c, I hope my
> > version is now `correct enough' to be usable [1]), and I made a simple
> > patch to make lseek SEEK_END (L_XTND in the source) dtrt on disk
> > devices too by simply invoking the DIOCGMEDIASIZE ioctl there; [2]
> > both of these things are what (some) Linux processes expect.
> >
> > Patches are here: (made on stable/8, if they don't apply on head
> > I'll have to make extra versions for that...)
> > http://people.freebsd.org/~nox/linuxdisk-blk.patch [1]
> > http://people.freebsd.org/~nox/lseek-seek_end.patch [2]
> >
> > And yes, with these patches the Linux bsdtar mentioned on -hackers
> > in the `"tar tfv /dev/cd0" speedup patch' thread now also runs fast
> > on FreeBSD. :)
>
> I now added an vn_isdisk() check to the second patch after comments from
> julian, and I made a new patch that adds an overflow check to the 32 bit
> linux lseek: (also at
> http://people.freebsd.org/~nox/linux-lseek-overflow.patch
> )
Hmm, when I asked Bruce, he actually said it was a feature that you didn't use
vn_isdisk(). He also suggested that the proper way to fix lseek on devices is
to fix stat in devfs to return a non-zero size. I have a possible fix to do
that but haven't tested it yet:
Index: devfs_vnops.c
===================================================================
--- devfs_vnops.c (revision 204207)
+++ devfs_vnops.c (working copy)
@@ -44,6 +44,7 @@
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/dirent.h>
+#include <sys/disk.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filedesc.h>
@@ -564,7 +565,11 @@
struct vattr *vap = ap->a_vap;
int error = 0;
struct devfs_dirent *de;
+ struct cdevsw *dsw;
+ struct thread *td;
+ struct file *fpop;
struct cdev *dev;
+ off_t size;
de = vp->v_data;
KASSERT(de != NULL, ("Null dirent in devfs_getattr vp=%p", vp));
@@ -612,6 +617,18 @@
vap->va_ctime = dev->si_ctime;
vap->va_rdev = cdev2priv(dev)->cdp_inode;
+
+ dsw = dev_refthread(dev);
+ if (dsw != NULL) {
+ td = curthread;
+ fpop = td->td_fpop;
+ td->td_fpop = NULL;
+ if (dsw->d_ioctl(dev, DIOCGMEDIASIZE, (caddr_t)&size,
+ FREAD, td) == 0)
+ vap->va_size = size;
+ td->td_fpop = fpop;
+ dev_relthread(dev);
+ }
}
vap->va_gen = 0;
vap->va_flags = 0;
--
John Baldwin
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