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Message-ID: <167391063242.2311931.3275290816918213423.stgit@warthog.procyon.org.uk>
Date: Mon, 16 Jan 2023 23:10:32 +0000
From: David Howells <dhowells@...hat.com>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: Dominique Martinet <asmadeus@...ewreck.org>,
Eric Van Hensbergen <ericvh@...il.com>,
Latchesar Ionkov <lucho@...kov.net>,
Christian Schoenebeck <linux_oss@...debyte.com>,
v9fs-developer@...ts.sourceforge.net, dhowells@...hat.com,
Christoph Hellwig <hch@...radead.org>,
Matthew Wilcox <willy@...radead.org>,
Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
Jeff Layton <jlayton@...nel.org>,
Logan Gunthorpe <logang@...tatee.com>,
linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v6 21/34] 9p: Pin pages rather than ref'ing if appropriate
Convert the 9p filesystem to use iov_iter_extract_pages() instead of
iov_iter_get_pages(). This will pin pages or leave them unaltered rather
than getting a ref on them as appropriate to the iterator.
The pages need to be pinned for DIO-read rather than having refs taken on
them to prevent VM copy-on-write from malfunctioning during a concurrent
fork() (the result of the I/O would otherwise end up only visible to the
child process and not the parent).
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Dominique Martinet <asmadeus@...ewreck.org>
cc: Eric Van Hensbergen <ericvh@...il.com>
cc: Latchesar Ionkov <lucho@...kov.net>
cc: Christian Schoenebeck <linux_oss@...debyte.com>
cc: v9fs-developer@...ts.sourceforge.net
---
net/9p/trans_common.c | 6 ++-
net/9p/trans_common.h | 3 +-
net/9p/trans_virtio.c | 89 ++++++++++++++-----------------------------------
3 files changed, 31 insertions(+), 67 deletions(-)
diff --git a/net/9p/trans_common.c b/net/9p/trans_common.c
index c827f694551c..31d133412677 100644
--- a/net/9p/trans_common.c
+++ b/net/9p/trans_common.c
@@ -12,13 +12,15 @@
* p9_release_pages - Release pages after the transaction.
* @pages: array of pages to be put
* @nr_pages: size of array
+ * @cleanup_mode: How to clean up the pages.
*/
-void p9_release_pages(struct page **pages, int nr_pages)
+void p9_release_pages(struct page **pages, int nr_pages,
+ unsigned int cleanup_mode)
{
int i;
for (i = 0; i < nr_pages; i++)
if (pages[i])
- put_page(pages[i]);
+ page_put_unpin(pages[i], cleanup_mode);
}
EXPORT_SYMBOL(p9_release_pages);
diff --git a/net/9p/trans_common.h b/net/9p/trans_common.h
index 32134db6abf3..9b20eb4f2359 100644
--- a/net/9p/trans_common.h
+++ b/net/9p/trans_common.h
@@ -4,4 +4,5 @@
* Author Venkateswararao Jujjuri <jvrao@...ux.vnet.ibm.com>
*/
-void p9_release_pages(struct page **pages, int nr_pages);
+void p9_release_pages(struct page **pages, int nr_pages,
+ unsigned int cleanup_mode);
diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index eb28b54fe5f6..561f7cbd79da 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -310,73 +310,34 @@ static int p9_get_mapped_pages(struct virtio_chan *chan,
struct iov_iter *data,
int count,
size_t *offs,
- int *need_drop,
+ int *cleanup_mode,
unsigned int gup_flags)
{
int nr_pages;
int err;
+ int n;
if (!iov_iter_count(data))
return 0;
- if (!iov_iter_is_kvec(data)) {
- int n;
- /*
- * We allow only p9_max_pages pinned. We wait for the
- * Other zc request to finish here
- */
- if (atomic_read(&vp_pinned) >= chan->p9_max_pages) {
- err = wait_event_killable(vp_wq,
- (atomic_read(&vp_pinned) < chan->p9_max_pages));
- if (err == -ERESTARTSYS)
- return err;
- }
- n = iov_iter_get_pages_alloc(data, pages, count, offs,
- gup_flags);
- if (n < 0)
- return n;
- *need_drop = 1;
- nr_pages = DIV_ROUND_UP(n + *offs, PAGE_SIZE);
- atomic_add(nr_pages, &vp_pinned);
- return n;
- } else {
- /* kernel buffer, no need to pin pages */
- int index;
- size_t len;
- void *p;
-
- /* we'd already checked that it's non-empty */
- while (1) {
- len = iov_iter_single_seg_count(data);
- if (likely(len)) {
- p = data->kvec->iov_base + data->iov_offset;
- break;
- }
- iov_iter_advance(data, 0);
- }
- if (len > count)
- len = count;
-
- nr_pages = DIV_ROUND_UP((unsigned long)p + len, PAGE_SIZE) -
- (unsigned long)p / PAGE_SIZE;
-
- *pages = kmalloc_array(nr_pages, sizeof(struct page *),
- GFP_NOFS);
- if (!*pages)
- return -ENOMEM;
-
- *need_drop = 0;
- p -= (*offs = offset_in_page(p));
- for (index = 0; index < nr_pages; index++) {
- if (is_vmalloc_addr(p))
- (*pages)[index] = vmalloc_to_page(p);
- else
- (*pages)[index] = kmap_to_page(p);
- p += PAGE_SIZE;
- }
- iov_iter_advance(data, len);
- return len;
+ /*
+ * We allow only p9_max_pages pinned. We wait for the
+ * Other zc request to finish here
+ */
+ if (atomic_read(&vp_pinned) >= chan->p9_max_pages) {
+ err = wait_event_killable(vp_wq,
+ (atomic_read(&vp_pinned) < chan->p9_max_pages));
+ if (err == -ERESTARTSYS)
+ return err;
}
+
+ n = iov_iter_extract_pages(data, pages, count, offs, gup_flags);
+ if (n < 0)
+ return n;
+ *cleanup_mode = iov_iter_extract_mode(data, gup_flags);
+ nr_pages = DIV_ROUND_UP(n + *offs, PAGE_SIZE);
+ atomic_add(nr_pages, &vp_pinned);
+ return n;
}
static void handle_rerror(struct p9_req_t *req, int in_hdr_len,
@@ -431,7 +392,7 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
struct virtio_chan *chan = client->trans;
struct scatterlist *sgs[4];
size_t offs;
- int need_drop = 0;
+ int cleanup_mode = 0;
int kicked = 0;
p9_debug(P9_DEBUG_TRANS, "virtio request\n");
@@ -439,7 +400,7 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
if (uodata) {
__le32 sz;
int n = p9_get_mapped_pages(chan, &out_pages, uodata,
- outlen, &offs, &need_drop,
+ outlen, &offs, &cleanup_mode,
FOLL_DEST_BUF);
if (n < 0) {
err = n;
@@ -459,7 +420,7 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
memcpy(&req->tc.sdata[0], &sz, sizeof(sz));
} else if (uidata) {
int n = p9_get_mapped_pages(chan, &in_pages, uidata,
- inlen, &offs, &need_drop,
+ inlen, &offs, &cleanup_mode,
FOLL_SOURCE_BUF);
if (n < 0) {
err = n;
@@ -546,14 +507,14 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
* Non kernel buffers are pinned, unpin them
*/
err_out:
- if (need_drop) {
+ if (cleanup_mode) {
if (in_pages) {
p9_release_pages(in_pages, in_nr_pages);
- atomic_sub(in_nr_pages, &vp_pinned);
+ atomic_sub(in_nr_pages, &vp_pinned, cleanup_mode);
}
if (out_pages) {
p9_release_pages(out_pages, out_nr_pages);
- atomic_sub(out_nr_pages, &vp_pinned);
+ atomic_sub(out_nr_pages, &vp_pinned, cleanup_mode);
}
/* wakeup anybody waiting for slots to pin pages */
wake_up(&vp_wq);
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