linux-kernel - RE: [Patch v2 02/15] CIFS: Add support for direct pages in rdata

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Date:   Wed, 30 May 2018 20:57:59 +0000
From:   Long Li <longli@...rosoft.com>
To:     "Ruhl, Michael J" <michael.j.ruhl@...el.com>,
        Steve French <sfrench@...ba.org>,
        "linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>,
        "samba-technical@...ts.samba.org" <samba-technical@...ts.samba.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
Subject: RE: [Patch v2 02/15] CIFS: Add support for direct pages in rdata

> Subject: RE: [Patch v2 02/15] CIFS: Add support for direct pages in rdata
> 
> >-----Original Message-----
> >From: linux-rdma-owner@...r.kernel.org [mailto:linux-rdma-
> >owner@...r.kernel.org] On Behalf Of Long Li
> >Sent: Wednesday, May 30, 2018 3:48 PM
> >To: Steve French <sfrench@...ba.org>; linux-cifs@...r.kernel.org;
> >samba- technical@...ts.samba.org; linux-kernel@...r.kernel.org; linux-
> >rdma@...r.kernel.org
> >Cc: Long Li <longli@...rosoft.com>
> >Subject: [Patch v2 02/15] CIFS: Add support for direct pages in rdata
> >
> >From: Long Li <longli@...rosoft.com>
> >
> >Add a function to allocate rdata without allocating pages for data
> >transfer. This gives the caller an option to pass a number of pages
> >that point to the data buffer.
> >
> >rdata is still reponsible for free those pages after it's done.
> >
> >Signed-off-by: Long Li <longli@...rosoft.com>
> >---
> > fs/cifs/cifsglob.h |  2 +-
> > fs/cifs/file.c     | 23 ++++++++++++++++++++---
> > 2 files changed, 21 insertions(+), 4 deletions(-)
> >
> >diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index
> >8d16c3e..56864a87 100644
> >--- a/fs/cifs/cifsglob.h
> >+++ b/fs/cifs/cifsglob.h
> >@@ -1179,7 +1179,7 @@ struct cifs_readdata {
> > 	unsigned int			tailsz;
> > 	unsigned int			credits;
> > 	unsigned int			nr_pages;
> >-	struct page			*pages[];
> >+	struct page			**pages;
> > };
> >
> > struct cifs_writedata;
> >diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 23fd430..1c98293
> >100644
> >--- a/fs/cifs/file.c
> >+++ b/fs/cifs/file.c
> >@@ -2880,13 +2880,13 @@ cifs_strict_writev(struct kiocb *iocb, struct
> >iov_iter *from)  }
> >
> > static struct cifs_readdata *
> >-cifs_readdata_alloc(unsigned int nr_pages, work_func_t complete)
> >+cifs_readdata_direct_alloc(struct page **pages, work_func_t complete)
> > {
> > 	struct cifs_readdata *rdata;
> >
> >-	rdata = kzalloc(sizeof(*rdata) + (sizeof(struct page *) * nr_pages),
> >-			GFP_KERNEL);
> >+	rdata = kzalloc(sizeof(*rdata), GFP_KERNEL);
> > 	if (rdata != NULL) {
> >+		rdata->pages = pages;
> > 		kref_init(&rdata->refcount);
> > 		INIT_LIST_HEAD(&rdata->list);
> > 		init_completion(&rdata->done);
> >@@ -2896,6 +2896,22 @@ cifs_readdata_alloc(unsigned int nr_pages,
> >work_func_t complete)
> > 	return rdata;
> > }
> >
> >+static struct cifs_readdata *
> >+cifs_readdata_alloc(unsigned int nr_pages, work_func_t complete) {
> >+	struct page **pages =
> >+		kzalloc(sizeof(struct page *) * nr_pages, GFP_KERNEL);
> >+	struct cifs_readdata *ret = NULL;
> >+
> >+	if (pages) {
> >+		ret = cifs_readdata_direct_alloc(pages, complete);
> >+		if (!ret)
> >+			kfree(pages);
> >+	}
> >+
> >+	return ret;
> >+}
> >+
> > void
> > cifs_readdata_release(struct kref *refcount)  { @@ -2910,6 +2926,7 @@
> >cifs_readdata_release(struct kref *refcount)
> > 	if (rdata->cfile)
> > 		cifsFileInfo_put(rdata->cfile);
> >
> >+	kvfree(rdata->pages);
> 
> Is the kvfree() correct?
> 
> You use kzalloc() and kfree in cifs_readdata_alloc().

This function is shared by both non-direct I/O and direct I/O code paths.

Direct I/O uses kvmalloc to allocate pages, so kvfree is used here to handle both cases.

> 
> Mike
> 
> > 	kfree(rdata);
> > }
> >
> >--
> >2.7.4
> >
> >--
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