Subject: MAXBSIZE Was Re: bread() returns EINVAL during vfs mount
To: Bill Studenmund <firstname.lastname@example.org>
From: Reinoud Zandijk <email@example.com>
Date: 08/27/2005 17:56:44
Content-Type: text/plain; charset=us-ascii
On Mon, Aug 22, 2005 at 02:49:19PM -0700, Bill Studenmund wrote:
> On Sat, Aug 20, 2005 at 09:47:18PM -0500, Yevgeny Binder wrote:
> > I've tried to follow the ffs code closely while developing hfs+
> > support, so it stumped me when I found that bread() invariably
> > returns EINVAL in my VFS mount routine. I have a valid pointer to the
> > volume's device node, devvp, obtained using the same ffs code:
> > NDINIT(ndp, LOOKUP, FOLLOW, UIO_USERSPACE, args.fspec, p);
> > if ((error = namei(ndp)) != 0)
> > return error;
> > devvp = ndp->ni_vp;
> > ndp comes from the mount arguments, and args.fspec is presently set
> > to "/dev/cd0a". I open this node and flush it:
HFS+ on CD? i found one recently but thought it was such an oddity.
Aparently not :) I found the disc to be formatted with HFS+ and UDF and
found the UDF part to be corrupt.
> > error = bread(devvp, 16, 1536, cred, &bp);
> The problem is that pread() permits i/o access that is not permitted with
> the buffer cache system. So it covers over issues that bread() won't.
> The problem is that you have to read full blocks. On a CD, that means 2k.
> 1536 is not an integer number of blocks, thus an EINVAL error.
not nessisarily 2k! though mostly used when writing CD's in streaming and
packet mode. I dont know about HFS+ but the UDF filingsystem supports every
multiple of 512 bytes as sector size though allways the same as the device
has, and yes 7680 bytes/sector is valid as is 1536 :-S
I wonder how i can implement sector sizes bigger than MAXBSIZE (normally
around 4k AFAIK) with normal bread and bwrite calls though.
> I think the problem is that you have drawn inspiration from file systems
> that never face this issue. If someone ever built an ffs file system on a
> CD, it would use 2k blocks, so all i/o would be 2k by nature and this
> issue would never come up. :-|
hmm i tried FFS on a CD-MRW only to be shot in the back by the CD disklabel
code that allways and only thinks iso9660 is the only valid thing on disc.
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