From: David Howells <dhowells@redhat.com>
To: torvalds@linux-foundation.org
Cc: dhowells@redhat.com,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Casey Schaufler <casey@schaufler-ca.com>,
Stephen Smalley <sds@tycho.nsa.gov>,
nicolas.dichtel@6wind.com, raven@themaw.net,
Christian Brauner <christian@brauner.io>,
dhowells@redhat.com, keyrings@vger.kernel.org,
linux-usb@vger.kernel.org, linux-block@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications [ver #2]
Date: Thu, 07 Nov 2019 13:36:33 +0000 [thread overview]
Message-ID: <157313379331.29677.5209561321495531328.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <157313371694.29677.15388731274912671071.stgit@warthog.procyon.org.uk>
Allow a buffer to be marked such that read() must return the entire buffer
in one go or return ENOBUFS. Multiple buffers can be amalgamated into a
single read, but a short read will occur if the next "whole" buffer won't
fit.
This is useful for watch queue notifications to make sure we don't split a
notification across multiple reads, especially given that we need to
fabricate an overrun record under some circumstances - and that isn't in
the buffers.
Signed-off-by: David Howells <dhowells@redhat.com>
---
fs/pipe.c | 8 +++++++-
include/linux/pipe_fs_i.h | 1 +
kernel/watch_queue.c | 2 +-
samples/watch_queue/watch_test.c | 2 +-
4 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/fs/pipe.c b/fs/pipe.c
index 099bf4b657dd..588355c24ee0 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -298,8 +298,14 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
size_t written;
int error;
- if (chars > total_len)
+ if (chars > total_len) {
+ if (buf->flags & PIPE_BUF_FLAG_WHOLE) {
+ if (ret == 0)
+ ret = -ENOBUFS;
+ break;
+ }
chars = total_len;
+ }
error = pipe_buf_confirm(pipe, buf);
if (error) {
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 816bc0d3aecd..a19d60a06869 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -8,6 +8,7 @@
#define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */
#define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */
#define PIPE_BUF_FLAG_PACKET 0x08 /* read() as a packet */
+#define PIPE_BUF_FLAG_WHOLE 0x10 /* read() must return entire buffer or error */
/**
* struct pipe_buffer - a linux kernel pipe buffer
diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index b73fbfe0d467..b1d30296e29b 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -115,7 +115,7 @@ static bool post_one_notification(struct watch_queue *wqueue,
buf->ops = &watch_queue_pipe_buf_ops;
buf->offset = offset;
buf->len = len;
- buf->flags = 0;
+ buf->flags = PIPE_BUF_FLAG_WHOLE;
pipe->head = head + 1;
if (!test_and_clear_bit(note, wqueue->notes_bitmap)) {
diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c
index 8925593bdb9b..f6fb6e813551 100644
--- a/samples/watch_queue/watch_test.c
+++ b/samples/watch_queue/watch_test.c
@@ -63,7 +63,7 @@ static void saw_key_change(struct watch_notification *n, size_t len)
*/
static void consumer(int fd)
{
- unsigned char buffer[4096], *p, *end;
+ unsigned char buffer[433], *p, *end;
union {
struct watch_notification n;
unsigned char buf1[128];
next prev parent reply other threads:[~2019-11-07 13:36 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-07 13:35 [RFC PATCH 00/14] pipe: Keyrings, Block and USB notifications [ver #2] David Howells
2019-11-07 13:35 ` [RFC PATCH 01/14] uapi: General notification queue definitions " David Howells
2019-11-07 13:35 ` [RFC PATCH 02/14] security: Add hooks to rule on setting a watch " David Howells
2019-11-07 13:35 ` [RFC PATCH 03/14] security: Add a hook for the point of notification insertion " David Howells
2019-11-07 13:35 ` [RFC PATCH 04/14] pipe: Add O_NOTIFICATION_PIPE " David Howells
2019-11-07 18:16 ` Andy Lutomirski
2019-11-07 18:48 ` David Howells
2019-11-08 5:06 ` Andy Lutomirski
2019-11-08 6:42 ` David Howells
2019-11-07 13:36 ` [RFC PATCH 05/14] pipe: Add general notification queue support " David Howells
2019-11-07 13:36 ` [RFC PATCH 06/14] keys: Add a notification facility " David Howells
2019-11-07 13:36 ` [RFC PATCH 07/14] Add sample notification program " David Howells
2019-11-07 13:36 ` David Howells [this message]
2019-11-07 18:15 ` [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications " Andy Lutomirski
2019-11-07 18:23 ` David Howells
2019-11-07 13:36 ` [RFC PATCH 09/14] pipe: Add notification lossage handling " David Howells
2019-11-07 13:36 ` [RFC PATCH 10/14] Add a general, global device notification watch list " David Howells
2019-11-07 13:37 ` [RFC PATCH 11/14] block: Add block layer notifications " David Howells
2019-11-07 13:37 ` [RFC PATCH 12/14] usb: Add USB subsystem " David Howells
2019-11-07 13:37 ` [RFC PATCH 13/14] selinux: Implement the watch_key security hook " David Howells
2019-11-07 13:37 ` [RFC PATCH 14/14] smack: Implement the watch_key and post_notification hooks " David Howells
2019-11-07 17:16 ` [RFC PATCH 05/14] pipe: Add general notification queue support " David Howells
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