Apparently as of version 2.42, glibc headers define AT_RENAME_NOREPLACE
and some of the other flags for renameat2() and friends in <stdio.h>.
Which would all be fine, except for inexplicable reasons glibc decided
to define them _differently_ from the kernel definitions, which then
makes some of our sample code that includes both kernel headers and user
space headers unhappy, because the compiler will (correctly) complain
about redefining things.
Now, mixing kernel headers and user space headers is always a somewhat
iffy proposition due to namespacing issues, but it's kind of inevitable
in our sample and selftest code. And this is just glibc being stupid.
Those defines come from the kernel, glibc is exposing the kernel
interfaces, and glibc shouldn't make up some random new expressions for
these values.
It's not like glibc headers changed the actual result values, but they
arbitrarily just decided to use a different expression to describe those
values. The kernel just does
#define AT_RENAME_NOREPLACE 0x0001
while glibc does
# define RENAME_NOREPLACE (1 << 0)
# define AT_RENAME_NOREPLACE RENAME_NOREPLACE
instead. Same value in the end, but very different macro definition.
For absolutely no reason.
This has since been fixed in the glibc development tree, so eventually
we'll end up with the canonical expressions and no clashes. But in the
meantime the broken headers are in the glibc-2.42 release and have made
it out into distributions.
Do a minimal work-around to make the samples build cleanly by just
undefining the affected macros in between the user space header include
and the kernel header includes.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The merged API doesn't use a watch_queue device, but instead relies on
pipes, so let the documentation reflect that.
Fixes: f7e47677e3 ("watch_queue: Add a key/keyring notification facility")
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Ben Boeckel <mathstuf@gmail.com>
Add handling for loss of notifications by having read() insert a
loss-notification message after it has read the pipe buffer that was last
in the ring when the loss occurred.
Lossage can come about either by running out of notification descriptors or
by running out of space in the pipe ring.
Signed-off-by: David Howells <dhowells@redhat.com>
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>
The sample program is run like:
./samples/watch_queue/watch_test
and watches "/" for mount changes and the current session keyring for key
changes:
# keyctl add user a a @s
1035096409
# keyctl unlink 1035096409 @s
producing:
# ./watch_test
read() = 16
NOTIFY[000]: ty=000001 sy=02 i=00000110
KEY 2ffc2e5d change=2[linked] aux=1035096409
read() = 16
NOTIFY[000]: ty=000001 sy=02 i=00000110
KEY 2ffc2e5d change=3[unlinked] aux=1035096409
Other events may be produced, such as with a failing disk:
read() = 22
NOTIFY[000]: ty=000003 sy=02 i=00000416
USB 3-7.7 dev-reset e=0 r=0
read() = 24
NOTIFY[000]: ty=000002 sy=06 i=00000418
BLOCK 00800050 e=6[critical medium] s=64000ef8
This corresponds to:
blk_update_request: critical medium error, dev sdf, sector 1677725432 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
in dmesg.
Signed-off-by: David Howells <dhowells@redhat.com>
