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Message-ID: <2856724.1641491044@warthog.procyon.org.uk>
Date: Thu, 06 Jan 2022 17:44:04 +0000
From: David Howells <dhowells@...hat.com>
To: Jeff Layton <jlayton@...nel.org>
Cc: dhowells@...hat.com, linux-cachefs@...hat.com,
Trond Myklebust <trondmy@...merspace.com>,
Anna Schumaker <anna.schumaker@...app.com>,
Steve French <sfrench@...ba.org>,
Dominique Martinet <asmadeus@...ewreck.org>,
Matthew Wilcox <willy@...radead.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Omar Sandoval <osandov@...ndov.com>,
JeffleXu <jefflexu@...ux.alibaba.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-afs@...ts.infradead.org, linux-nfs@...r.kernel.org,
linux-cifs@...r.kernel.org, ceph-devel@...r.kernel.org,
v9fs-developer@...ts.sourceforge.net,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 40/68] cachefiles: Implement cache registration and withdrawal
Jeff Layton <jlayton@...nel.org> wrote:
> > + /* check parameters */
> > + ret = -EOPNOTSUPP;
> > + if (d_is_negative(root) ||
> > + !d_backing_inode(root)->i_op->lookup ||
> > + !d_backing_inode(root)->i_op->mkdir ||
> > + !(d_backing_inode(root)->i_opflags & IOP_XATTR) ||
> > + !root->d_sb->s_op->statfs ||
> > + !root->d_sb->s_op->sync_fs ||
> > + root->d_sb->s_blocksize > PAGE_SIZE)
> > + goto error_unsupported;
> > +
>
> That's quite a collection of tests.
>
> Most are obvious, but some comments explaining the need for others would
> not be a bad thing. In particular, why is s_blocksize > PAGE_SIZE
> unsupported?
It can't do page-sized DIO requests to a filesystem with a block size larger
than a page. In the future I can work around that in conjunction with
netfslib by expanding read and write sizes.
> Also, should you vet whether the fs supports i_op->tmpfile here ?
That's a good idea.
David
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