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Message-ID: <x49k1wmdcxn.fsf@segfault.boston.devel.redhat.com>
Date: Fri, 12 Jan 2018 15:44:52 -0500
From: Jeff Moyer <jmoyer@...hat.com>
To: Christoph Hellwig <hch@....de>
Cc: viro@...iv.linux.org.uk, Avi Kivity <avi@...lladb.com>,
linux-aio@...ck.org, linux-fsdevel@...r.kernel.org,
netdev@...r.kernel.org, linux-api@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 32/32] aio: implement io_pgetevents
Christoph Hellwig <hch@....de> writes:
> This is the io_getevents equivalent of ppoll/pselect and allows to
> properly mix signals and aio completions (especially with IOCB_CMD_POLL)
> and atomically executes the following sequence:
>
> sigset_t origmask;
>
> pthread_sigmask(SIG_SETMASK, &sigmask, &origmask);
> ret = io_getevents(ctx, min_nr, nr, events, timeout);
> pthread_sigmask(SIG_SETMASK, &origmask, NULL);
>
> Note that unlike many other signal related calls we do not pass a sigmask
> size, as that would get us to 7 arguments, which aren't easily supported
> by the syscall infrastructure. It seems a lot less painful to just add a
> new syscall variant in the unlikely case we're going to increase the
> sigset size.
pselect, as an example, crams the sigmask and size together. Why not
just do that? libaio can take care of setting that up.
Cheers,
Jeff
>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
> arch/x86/entry/syscalls/syscall_32.tbl | 1 +
> arch/x86/entry/syscalls/syscall_64.tbl | 1 +
> fs/aio.c | 96 ++++++++++++++++++++++++++++++----
> include/linux/compat.h | 6 +++
> include/linux/syscalls.h | 6 +++
> include/uapi/asm-generic/unistd.h | 4 +-
> kernel/sys_ni.c | 2 +
> 7 files changed, 105 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
> index 448ac2161112..5997c3e9ac3e 100644
> --- a/arch/x86/entry/syscalls/syscall_32.tbl
> +++ b/arch/x86/entry/syscalls/syscall_32.tbl
> @@ -391,3 +391,4 @@
> 382 i386 pkey_free sys_pkey_free
> 383 i386 statx sys_statx
> 384 i386 arch_prctl sys_arch_prctl compat_sys_arch_prctl
> +385 i386 io_pgetevents sys_io_pgetevents compat_sys_io_pgetevents
> diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
> index 5aef183e2f85..e995cd2b4e65 100644
> --- a/arch/x86/entry/syscalls/syscall_64.tbl
> +++ b/arch/x86/entry/syscalls/syscall_64.tbl
> @@ -339,6 +339,7 @@
> 330 common pkey_alloc sys_pkey_alloc
> 331 common pkey_free sys_pkey_free
> 332 common statx sys_statx
> +333 common io_pgetevents sys_io_pgetevents
>
> #
> # x32-specific system call numbers start at 512 to avoid cache impact
> diff --git a/fs/aio.c b/fs/aio.c
> index cae90ac6e4a3..57a4e8d89f78 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1299,10 +1299,6 @@ static long read_events(struct kioctx *ctx, long min_nr, long nr,
> wait_event_interruptible_hrtimeout(ctx->wait,
> aio_read_events(ctx, min_nr, nr, event, &ret),
> until);
> -
> - if (!ret && signal_pending(current))
> - ret = -EINTR;
> -
> return ret;
> }
>
> @@ -1978,13 +1974,54 @@ SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
> struct timespec __user *, timeout)
> {
> struct timespec64 ts;
> + int ret;
> +
> + if (timeout && unlikely(get_timespec64(&ts, timeout)))
> + return -EFAULT;
>
> - if (timeout) {
> - if (unlikely(get_timespec64(&ts, timeout)))
> + ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
> + if (!ret && signal_pending(current))
> + ret = -EINTR;
> + return ret;
> +}
> +
> +SYSCALL_DEFINE6(io_pgetevents,
> + aio_context_t, ctx_id,
> + long, min_nr,
> + long, nr,
> + struct io_event __user *, events,
> + struct timespec __user *, timeout,
> + const sigset_t __user *, sigmask)
> +{
> + sigset_t ksigmask, sigsaved;
> + struct timespec64 ts;
> + int ret;
> +
> + if (timeout && unlikely(get_timespec64(&ts, timeout)))
> + return -EFAULT;
> +
> + if (sigmask) {
> + if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
> return -EFAULT;
> + sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
> + sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
> }
>
> - return do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
> + ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
> + if (signal_pending(current)) {
> + if (sigmask) {
> + current->saved_sigmask = sigsaved;
> + set_restore_sigmask();
> + }
> +
> + if (!ret)
> + ret = -ERESTARTNOHAND;
> + } else {
> + if (sigmask)
> + sigprocmask(SIG_SETMASK, &sigsaved, NULL);
> + }
> +
> + return ret;
> }
>
> #ifdef CONFIG_COMPAT
> @@ -1995,13 +2032,52 @@ COMPAT_SYSCALL_DEFINE5(io_getevents, compat_aio_context_t, ctx_id,
> struct compat_timespec __user *, timeout)
> {
> struct timespec64 t;
> + int ret;
> +
> + if (timeout && compat_get_timespec64(&t, timeout))
> + return -EFAULT;
> +
> + ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
> + if (!ret && signal_pending(current))
> + ret = -EINTR;
> + return ret;
> +}
> +
> +COMPAT_SYSCALL_DEFINE6(io_pgetevents,
> + compat_aio_context_t, ctx_id,
> + compat_long_t, min_nr,
> + compat_long_t, nr,
> + struct io_event __user *, events,
> + struct compat_timespec __user *, timeout,
> + const compat_sigset_t __user *, sigmask)
> +{
> + sigset_t ksigmask, sigsaved;
> + struct timespec64 t;
> + int ret;
>
> - if (timeout) {
> - if (compat_get_timespec64(&t, timeout))
> + if (timeout && compat_get_timespec64(&t, timeout))
> + return -EFAULT;
> +
> + if (sigmask) {
> + if (get_compat_sigset(&ksigmask, sigmask))
> return -EFAULT;
> + sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
> + sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
> + }
>
> + ret = do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
> + if (signal_pending(current)) {
> + if (sigmask) {
> + current->saved_sigmask = sigsaved;
> + set_restore_sigmask();
> + }
> + if (!ret)
> + ret = -ERESTARTNOHAND;
> + } else {
> + if (sigmask)
> + sigprocmask(SIG_SETMASK, &sigsaved, NULL);
> }
>
> - return do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
> + return ret;
> }
> #endif
> diff --git a/include/linux/compat.h b/include/linux/compat.h
> index 0fc36406f32c..a4cda98073f1 100644
> --- a/include/linux/compat.h
> +++ b/include/linux/compat.h
> @@ -536,6 +536,12 @@ asmlinkage long compat_sys_io_getevents(compat_aio_context_t ctx_id,
> compat_long_t nr,
> struct io_event __user *events,
> struct compat_timespec __user *timeout);
> +asmlinkage long compat_sys_io_pgetevents(compat_aio_context_t ctx_id,
> + compat_long_t min_nr,
> + compat_long_t nr,
> + struct io_event __user *events,
> + struct compat_timespec __user *timeout,
> + const compat_sigset_t __user *sigmask);
> asmlinkage long compat_sys_io_submit(compat_aio_context_t ctx_id, int nr,
> u32 __user *iocb);
> asmlinkage long compat_sys_mount(const char __user *dev_name,
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index a78186d826d7..3bc9a130f4a9 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -539,6 +539,12 @@ asmlinkage long sys_io_getevents(aio_context_t ctx_id,
> long nr,
> struct io_event __user *events,
> struct timespec __user *timeout);
> +asmlinkage long sys_io_pgetevents(aio_context_t ctx_id,
> + long min_nr,
> + long nr,
> + struct io_event __user *events,
> + struct timespec __user *timeout,
> + const sigset_t __user *sigmask);
> asmlinkage long sys_io_submit(aio_context_t, long,
> struct iocb __user * __user *);
> asmlinkage long sys_io_cancel(aio_context_t ctx_id, struct iocb __user *iocb,
> diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
> index 8b87de067bc7..ce2ebbeece10 100644
> --- a/include/uapi/asm-generic/unistd.h
> +++ b/include/uapi/asm-generic/unistd.h
> @@ -732,9 +732,11 @@ __SYSCALL(__NR_pkey_alloc, sys_pkey_alloc)
> __SYSCALL(__NR_pkey_free, sys_pkey_free)
> #define __NR_statx 291
> __SYSCALL(__NR_statx, sys_statx)
> +#define __NR_io_pgetevents 292
> +__SC_COMP(__NR_io_pgetevents, sys_io_pgetevents, compat_sys_io_pgetevents)
>
> #undef __NR_syscalls
> -#define __NR_syscalls 292
> +#define __NR_syscalls 293
>
> /*
> * All syscalls below here should go away really,
> diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
> index b5189762d275..8f7705559b38 100644
> --- a/kernel/sys_ni.c
> +++ b/kernel/sys_ni.c
> @@ -151,9 +151,11 @@ cond_syscall(sys_io_destroy);
> cond_syscall(sys_io_submit);
> cond_syscall(sys_io_cancel);
> cond_syscall(sys_io_getevents);
> +cond_syscall(sys_io_pgetevents);
> cond_syscall(compat_sys_io_setup);
> cond_syscall(compat_sys_io_submit);
> cond_syscall(compat_sys_io_getevents);
> +cond_syscall(compat_sys_io_pgetevents);
> cond_syscall(sys_sysfs);
> cond_syscall(sys_syslog);
> cond_syscall(sys_process_vm_readv);
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