From patchwork Fri May 31 03:53:49 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kent Overstreet X-Patchwork-Id: 13681097 Received: from out-183.mta0.migadu.com (out-183.mta0.migadu.com [91.218.175.183]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 515EE14265 for ; Fri, 31 May 2024 03:53:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.183 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717127641; cv=none; b=XUIKjeg54eChAicVIjtB7B9kKnKtEHIlXIYvKNifb7XC6QBrUJ4oqaU9IbOicqLjiil5wZKFAh5U5U68rBw6gvo1+yqyTitDAn14yNgFIGH57CoTIV4E3vGb2k3KgbcRynzY/xqhKKy06X8acZOczlwA0YjxG/VgZY2eqsGYQ9g= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717127641; c=relaxed/simple; bh=gnks7OwAzc91drebCgibduBU0KOaUdki7hsFWSlPw4g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=IDQMAnGh1cGyPktK7rCrn+VpSlXRh9ndgdgUvjiuRu7TtI1Nlpx3I0t8vRX+Pj/RTTl+EdQDUAoSBJv6hzb+/r5WFALCcRjoSRZaIYzHJabhhUbJQkttLa4rfNgsz840ylaXHcBIJcFWJHN2Yyrp46jGRM80TOof51k3cL3sfzA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=fx3C8QP4; arc=none smtp.client-ip=91.218.175.183 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="fx3C8QP4" X-Envelope-To: bernd.schubert@fastmail.fm DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1717127634; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=3Q5205RitZvtxxsySDbK6v2N+MvxOAuX2elEr7D8Pgg=; b=fx3C8QP4DxT3YGDf7on+LqNmyRSLIkR24ZrZ1Jxy8RgukWonrmxOjb9aUzvcaYu8IpF1OD MIl4yUg1VcUROZQUfmxZc5o51LeZmka3RtmcqCSJLr5R/8aLe/4vADdGXLcKHHw8dpTcD8 v338HVajJdaBEvrdRuF0GDUClb0mlXE= X-Envelope-To: bschubert@ddn.com X-Envelope-To: miklos@szeredi.hu X-Envelope-To: amir73il@gmail.com X-Envelope-To: linux-fsdevel@vger.kernel.org X-Envelope-To: akpm@linux-foundation.org X-Envelope-To: linux-mm@kvack.org X-Envelope-To: mingo@redhat.com X-Envelope-To: peterz@infradead.org X-Envelope-To: avagin@google.com X-Envelope-To: io-uring@vger.kernel.org X-Envelope-To: axboe@kernel.dk X-Envelope-To: ming.lei@redhat.com X-Envelope-To: asml.silence@gmail.com X-Envelope-To: josef@toxicpanda.com Date: Thu, 30 May 2024 23:53:49 -0400 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Kent Overstreet To: Bernd Schubert Cc: Bernd Schubert , Miklos Szeredi , Amir Goldstein , linux-fsdevel@vger.kernel.org, Andrew Morton , linux-mm@kvack.org, Ingo Molnar , Peter Zijlstra , Andrei Vagin , io-uring@vger.kernel.org, Jens Axboe , Ming Lei , Pavel Begunkov , Josef Bacik Subject: [PATCH] fs: sys_ringbuffer() (WIP) Message-ID: References: <20240529-fuse-uring-for-6-9-rfc2-out-v1-0-d149476b1d65@ddn.com> <5mimjjxul2sc2g7x6pttnit46pbw3astwj2giqfr4xayp63el2@fb5bgtiavwgv> <8c3548a9-3b15-49c4-9e38-68d81433144a@fastmail.fm> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT On Thu, May 30, 2024 at 06:17:29PM +0200, Bernd Schubert wrote: > > > On 5/30/24 18:10, Kent Overstreet wrote: > > On Thu, May 30, 2024 at 06:02:21PM +0200, Bernd Schubert wrote: > >> Hmm, initially I had thought about writing my own ring buffer, but then > >> io-uring got IORING_OP_URING_CMD, which seems to have exactly what we > >> need? From interface point of view, io-uring seems easy to use here, > >> has everything we need and kind of the same thing is used for ublk - > >> what speaks against io-uring? And what other suggestion do you have? > >> > >> I guess the same concern would also apply to ublk_drv. > >> > >> Well, decoupling from io-uring might help to get for zero-copy, as there > >> doesn't seem to be an agreement with Mings approaches (sorry I'm only > >> silently following for now). > >> > >> From our side, a customer has pointed out security concerns for io-uring. > >> My thinking so far was to implemented the required io-uring pieces into > >> an module and access it with ioctls... Which would also allow to > >> backport it to RHEL8/RHEL9. > > > > Well, I've been starting to sketch out a ringbuffer() syscall, which > > would work on any (supported) file descriptor and give you a ringbuffer > > for reading or writing (or call it twice for both). > > > > That seems to be what fuse really wants, no? You're already using a file > > descriptor and your own RPC format, you just want a faster > > communications channel. > > Fine with me, if you have something better/simpler with less security > concerns - why not. We just need a community agreement on that. > > Do you have something I could look at? Here you go. Not tested yet, but all the essentials should be there. there's something else _really_ slick we should be able to do with this: add support to pipes, and then - if both ends of a pipe ask for a ringbuffer, map them the _same_ ringbuffer, zero copy and completely bypassing the kernel and neither end has to know if the other end supports ringbuffers or just normal pipes. -- >8 -- Add new syscalls for generic ringbuffers that can be attached to arbitrary (supporting) file descriptors. A ringbuffer consists of: - a single page for head/tail pointers, size/mask, and other ancilliary metadata, described by 'struct ringbuffer_ptrs' - a data buffer, consisting of one or more pages mapped at 'ringbuffer_ptrs.data_offset' above the address of 'ringbuffer_ptrs' The data buffer is always a power of two size. Head and tail pointers are u32 byte offsets, and they are stored unmasked (i.e., they use the full 32 bit range) - they must be masked for reading. - ringbuffer(int fd, int rw, u32 size, ulong *addr) Create or get address of an existing ringbuffer for either reads or writes, of at least size bytes, and attach it to the given file descriptor; the address of the ringbuffer is returned via addr. Since files can be shared between processes in different address spaces a ringbuffer may be mapped into multiple address spaces via this syscall. - ringbuffer_wait(int fd, int rw) Wait for space to be availaable (on a ringbuffer for writing), or data to be available (on a ringbuffer for writing). todo: add parameters for timeout, minimum amount of data/space to wait for - ringbuffer_wakeup(int fd, int rw) Required after writing to a previously empty ringbuffer, or reading from a previously full ringbuffer to notify waiters on the other end todo - investigate integrating with futexes? todo - add extra fields to ringbuffer_ptrs for waiting on a minimum amount of data/space, i.e. to signal when a wakeup is required Kernel interfaces: - To indicate that ringbuffers are supported on a file, set FOP_RINGBUFFER_READ and/or FOP_RINGBUFFER_WRITE in your file_operations. - To read or write to a file's associated ringbuffers (file->f_ringbuffer), use ringbuffer_read() or ringbuffer_write(). Signed-off-by: Kent Overstreet --- arch/x86/entry/syscalls/syscall_32.tbl | 3 + arch/x86/entry/syscalls/syscall_64.tbl | 3 + fs/Makefile | 1 + fs/file_table.c | 2 + fs/ringbuffer.c | 478 +++++++++++++++++++++++++ include/linux/fs.h | 14 + include/linux/mm_types.h | 4 + include/linux/ringbuffer_sys.h | 15 + include/uapi/linux/ringbuffer_sys.h | 38 ++ init/Kconfig | 8 + kernel/fork.c | 1 + 11 files changed, 567 insertions(+) create mode 100644 fs/ringbuffer.c create mode 100644 include/linux/ringbuffer_sys.h create mode 100644 include/uapi/linux/ringbuffer_sys.h diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index 7fd1f57ad3d3..2385359eaf75 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -467,3 +467,6 @@ 460 i386 lsm_set_self_attr sys_lsm_set_self_attr 461 i386 lsm_list_modules sys_lsm_list_modules 462 i386 mseal sys_mseal +463 i386 ringbuffer sys_ringbuffer +464 i386 ringbuffer_wait sys_ringbuffer_wait +465 i386 ringbuffer_wakeup sys_ringbuffer_wakeup diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index a396f6e6ab5b..942602ece075 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -384,6 +384,9 @@ 460 common lsm_set_self_attr sys_lsm_set_self_attr 461 common lsm_list_modules sys_lsm_list_modules 462 common mseal sys_mseal +463 common ringbuffer sys_ringbuffer +464 common ringbuffer_wait sys_ringbuffer_wait +465 common ringbuffer_wakeup sys_ringbuffer_wakeup # # Due to a historical design error, certain syscalls are numbered differently diff --git a/fs/Makefile b/fs/Makefile index 6ecc9b0a53f2..48e54ac01fb1 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -28,6 +28,7 @@ obj-$(CONFIG_TIMERFD) += timerfd.o obj-$(CONFIG_EVENTFD) += eventfd.o obj-$(CONFIG_USERFAULTFD) += userfaultfd.o obj-$(CONFIG_AIO) += aio.o +obj-$(CONFIG_RINGBUFFER) += ringbuffer.o obj-$(CONFIG_FS_DAX) += dax.o obj-$(CONFIG_FS_ENCRYPTION) += crypto/ obj-$(CONFIG_FS_VERITY) += verity/ diff --git a/fs/file_table.c b/fs/file_table.c index 4f03beed4737..9675f22d6615 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #include #include @@ -412,6 +413,7 @@ static void __fput(struct file *file) */ eventpoll_release(file); locks_remove_file(file); + ringbuffer_file_exit(file); security_file_release(file); if (unlikely(file->f_flags & FASYNC)) { diff --git a/fs/ringbuffer.c b/fs/ringbuffer.c new file mode 100644 index 000000000000..cef8ca8b9416 --- /dev/null +++ b/fs/ringbuffer.c @@ -0,0 +1,478 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define RINGBUFFER_FS_MAGIC 0xa10a10a2 + +static DEFINE_MUTEX(ringbuffer_lock); + +static struct vfsmount *ringbuffer_mnt; + +struct ringbuffer_mapping { + ulong addr; + struct mm_struct *mm; +}; + +struct ringbuffer { + wait_queue_head_t wait[2]; + spinlock_t lock; + int rw; + u32 size; /* always a power of two */ + u32 mask; /* size - 1 */ + struct file *io_file; + /* hidden internal file for the mmap */ + struct file *rb_file; + struct ringbuffer_ptrs *ptrs; + void *data; + DARRAY(struct ringbuffer_mapping) mms; +}; + +static const struct address_space_operations ringbuffer_aops = { + .dirty_folio = noop_dirty_folio, +#if 0 + .migrate_folio = ringbuffer_migrate_folio, +#endif +}; + +#if 0 +static int ringbuffer_mremap(struct vm_area_struct *vma) +{ + struct file *file = vma->vm_file; + struct mm_struct *mm = vma->vm_mm; + struct kioctx_table *table; + int i, res = -EINVAL; + + spin_lock(&mm->ioctx_lock); + rcu_read_lock(); + table = rcu_dereference(mm->ioctx_table); + if (!table) + goto out_unlock; + + for (i = 0; i < table->nr; i++) { + struct kioctx *ctx; + + ctx = rcu_dereference(table->table[i]); + if (ctx && ctx->ringbuffer_file == file) { + if (!atomic_read(&ctx->dead)) { + ctx->user_id = ctx->mmap_base = vma->vm_start; + res = 0; + } + break; + } + } + +out_unlock: + rcu_read_unlock(); + spin_unlock(&mm->ioctx_lock); + return res; +} +#endif + +static const struct vm_operations_struct ringbuffer_vm_ops = { +#if 0 + .mremap = ringbuffer_mremap, +#endif +#if IS_ENABLED(CONFIG_MMU) + .fault = filemap_fault, + .map_pages = filemap_map_pages, + .page_mkwrite = filemap_page_mkwrite, +#endif +}; + +static int ringbuffer_mmap(struct file *file, struct vm_area_struct *vma) +{ + vm_flags_set(vma, VM_DONTEXPAND); + vma->vm_ops = &ringbuffer_vm_ops; + return 0; +} + +static const struct file_operations ringbuffer_fops = { + .mmap = ringbuffer_mmap, +}; + +static void ringbuffer_free(struct ringbuffer *rb) +{ + rb->io_file->f_ringbuffers[rb->rw] = NULL; + + darray_for_each(rb->mms, map) + darray_for_each_reverse(map->mm->ringbuffers, rb2) + if (rb == *rb2) + darray_remove_item(&map->mm->ringbuffers, rb2); + + if (rb->rb_file) { + /* Kills mapping: */ + truncate_setsize(file_inode(rb->rb_file), 0); + + /* Prevent further access to the kioctx from migratepages */ + struct address_space *mapping = rb->rb_file->f_mapping; + spin_lock(&mapping->i_private_lock); + mapping->i_private_data = NULL; + spin_unlock(&mapping->i_private_lock); + + fput(rb->rb_file); + } + + free_pages((ulong) rb->data, get_order(rb->size)); + free_page((ulong) rb->ptrs); + kfree(rb); +} + +static int ringbuffer_map(struct ringbuffer *rb, ulong *addr) +{ + struct mm_struct *mm = current->mm; + + int ret = darray_make_room(&rb->mms, 1) ?: + darray_make_room(&mm->ringbuffers, 1); + if (ret) + return ret; + + ret = mmap_write_lock_killable(mm); + if (ret) + return ret; + + ulong unused; + struct ringbuffer_mapping map = { + .addr = do_mmap(rb->rb_file, 0, rb->size + PAGE_SIZE, + PROT_READ|PROT_WRITE, + MAP_SHARED, 0, 0, &unused, NULL), + .mm = mm, + }; + mmap_write_unlock(mm); + + ret = PTR_ERR_OR_ZERO((void *) map.addr); + if (ret) + return ret; + + ret = darray_push(&mm->ringbuffers, rb) ?: + darray_push(&rb->mms, map); + BUG_ON(ret); /* we preallocated */ + + *addr = map.addr; + return 0; +} + +static int ringbuffer_get_addr_or_map(struct ringbuffer *rb, ulong *addr) +{ + struct mm_struct *mm = current->mm; + + darray_for_each(rb->mms, map) + if (map->mm == mm) { + *addr = map->addr; + return 0; + } + + return ringbuffer_map(rb, addr); +} + +static struct ringbuffer *ringbuffer_alloc(struct file *file, int rw, u32 size, + ulong *addr) +{ + unsigned order = get_order(size); + size = PAGE_SIZE << order; + + struct ringbuffer *rb = kzalloc(sizeof(*rb), GFP_KERNEL); + if (!rb) + return ERR_PTR(-ENOMEM); + + init_waitqueue_head(&rb->wait[READ]); + init_waitqueue_head(&rb->wait[WRITE]); + spin_lock_init(&rb->lock); + rb->rw = rw; + rb->size = size; + rb->mask = size - 1; + rb->io_file = file; + + rb->ptrs = (void *) __get_free_page(GFP_KERNEL|__GFP_ZERO); + rb->data = (void *) __get_free_pages(GFP_KERNEL|__GFP_ZERO, order); + if (!rb->ptrs || !rb->data) + goto err; + + rb->ptrs->size = size; + rb->ptrs->mask = size - 1; + rb->ptrs->data_offset = PAGE_SIZE; + + struct inode *inode = alloc_anon_inode(ringbuffer_mnt->mnt_sb); + int ret = PTR_ERR_OR_ZERO(inode); + if (ret) + goto err; + + inode->i_mapping->a_ops = &ringbuffer_aops; + inode->i_mapping->i_private_data = rb; + inode->i_size = size; + + rb->rb_file = alloc_file_pseudo(inode, ringbuffer_mnt, "[ringbuffer]", + O_RDWR, &ringbuffer_fops); + ret = PTR_ERR_OR_ZERO(rb->rb_file); + if (ret) + goto err_iput; + + ret = filemap_add_folio(rb->rb_file->f_mapping, + page_folio(virt_to_page(rb->ptrs)), + 0, GFP_KERNEL); + if (ret) + goto err; + + /* todo - implement a fallback when high order allocation fails */ + ret = filemap_add_folio(rb->rb_file->f_mapping, + page_folio(virt_to_page(rb->data)), + 1, GFP_KERNEL); + if (ret) + goto err; + + ret = ringbuffer_map(rb, addr); + if (ret) + goto err; + + return rb; +err_iput: + iput(inode); +err: + ringbuffer_free(rb); + return ERR_PTR(ret); +} + +/* file is going away, tear down ringbuffers: */ +void ringbuffer_file_exit(struct file *file) +{ + mutex_lock(&ringbuffer_lock); + for (unsigned i = 0; i < ARRAY_SIZE(file->f_ringbuffers); i++) + if (file->f_ringbuffers[i]) + ringbuffer_free(file->f_ringbuffers[i]); + mutex_unlock(&ringbuffer_lock); +} + +/* + * XXX: we require synchronization when killing a ringbuffer (because no longer + * mapped anywhere) to a file that is still open (and in use) + */ +static void ringbuffer_mm_drop(struct mm_struct *mm, struct ringbuffer *rb) +{ + darray_for_each_reverse(rb->mms, map) + if (mm == map->mm) + darray_remove_item(&rb->mms, map); + + if (!rb->mms.nr) + ringbuffer_free(rb); +} + +void ringbuffer_mm_exit(struct mm_struct *mm) +{ + mutex_lock(&ringbuffer_lock); + darray_for_each_reverse(mm->ringbuffers, rb) + ringbuffer_mm_drop(mm, *rb); + mutex_unlock(&ringbuffer_lock); + + darray_exit(&mm->ringbuffers); +} + +SYSCALL_DEFINE4(ringbuffer, unsigned, fd, int, rw, u32, size, ulong __user *, ringbufferp) +{ + ulong rb_addr; + + int ret = get_user(rb_addr, ringbufferp); + if (unlikely(ret)) + return ret; + + if (unlikely(rb_addr || !size || rw > WRITE)) + return -EINVAL; + + struct fd f = fdget(fd); + if (!f.file) + return -EBADF; + + if (!(f.file->f_op->fop_flags & (rw == READ ? FOP_RINGBUFFER_READ : FOP_RINGBUFFER_WRITE))) { + ret = -EOPNOTSUPP; + goto err; + } + + mutex_lock(&ringbuffer_lock); + struct ringbuffer *rb = f.file->f_ringbuffers[rw]; + if (rb) { + ret = ringbuffer_get_addr_or_map(rb, &rb_addr); + if (ret) + goto err_unlock; + + ret = put_user(rb_addr, ringbufferp); + } else { + rb = ringbuffer_alloc(f.file, rw, size, &rb_addr); + ret = PTR_ERR_OR_ZERO(rb); + if (ret) + goto err_unlock; + + ret = put_user(rb_addr, ringbufferp); + if (ret) { + ringbuffer_free(rb); + goto err_unlock; + } + + f.file->f_ringbuffers[rw] = rb; + } +err_unlock: + mutex_unlock(&ringbuffer_lock); +err: + fdput(f); + return ret; +} + +static bool __ringbuffer_read(struct ringbuffer *rb, void **data, size_t *len, + bool nonblocking, size_t *ret) +{ + u32 head = rb->ptrs->head; + u32 tail = rb->ptrs->tail; + + if (head == tail) + return 0; + + ulong flags; + spin_lock_irqsave(&rb->lock, flags); + /* Multiple consumers - recheck under lock: */ + tail = rb->ptrs->tail; + + while (*len && tail != head) { + u32 tail_masked = tail & rb->mask; + u32 b = min(*len, + min(head - tail, + rb->size - tail_masked)); + + memcpy(*data, rb->data + tail_masked, b); + tail += b; + *data += b; + *len -= b; + *ret += b; + } + + smp_store_release(&rb->ptrs->tail, tail); + spin_unlock_irqrestore(&rb->lock, flags); + + return !*len || nonblocking; +} + +size_t ringbuffer_read(struct ringbuffer *rb, void *data, size_t len, bool nonblocking) +{ + size_t ret = 0; + wait_event(rb->wait[READ], __ringbuffer_read(rb, &data, &len, nonblocking, &ret)); + return ret; +} +EXPORT_SYMBOL_GPL(ringbuffer_read); + +static bool __ringbuffer_write(struct ringbuffer *rb, void **data, size_t *len, + bool nonblocking, size_t *ret) +{ + u32 head = rb->ptrs->head; + u32 tail = rb->ptrs->tail; + + if (head - tail >= rb->size) + return 0; + + ulong flags; + spin_lock_irqsave(&rb->lock, flags); + /* Multiple producers - recheck under lock: */ + head = rb->ptrs->head; + + while (*len && head - tail < rb->size) { + u32 head_masked = head & rb->mask; + u32 b = min(*len, + min(tail + rb->size - head, + rb->size - head_masked)); + + memcpy(rb->data + head_masked, *data, b); + head += b; + *data += b; + *len -= b; + *ret += b; + } + + smp_store_release(&rb->ptrs->head, head); + spin_unlock_irqrestore(&rb->lock, flags); + + return !*len || nonblocking; +} + +size_t ringbuffer_write(struct ringbuffer *rb, void *data, size_t len, bool nonblocking) +{ + size_t ret = 0; + wait_event(rb->wait[WRITE], __ringbuffer_write(rb, &data, &len, nonblocking, &ret)); + return ret; +} +EXPORT_SYMBOL_GPL(ringbuffer_write); + +SYSCALL_DEFINE2(ringbuffer_wait, unsigned, fd, int, rw) +{ + int ret = 0; + + if (rw > WRITE) + return -EINVAL; + + struct fd f = fdget(fd); + if (!f.file) + return -EBADF; + + struct ringbuffer *rb = f.file->f_ringbuffers[rw]; + if (!rb) { + ret = -EINVAL; + goto err; + } + + struct ringbuffer_ptrs *rp = rb->ptrs; + wait_event(rb->wait[rw], rw == READ + ? rp->head != rp->tail + : rp->head - rp->tail < rb->size); +err: + fdput(f); + return ret; +} + +SYSCALL_DEFINE2(ringbuffer_wakeup, unsigned, fd, int, rw) +{ + int ret = 0; + + if (rw > WRITE) + return -EINVAL; + + struct fd f = fdget(fd); + if (!f.file) + return -EBADF; + + struct ringbuffer *rb = f.file->f_ringbuffers[rw]; + if (!rb) { + ret = -EINVAL; + goto err; + } + + wake_up(&rb->wait[rw]); +err: + fdput(f); + return ret; +} + +static int ringbuffer_init_fs_context(struct fs_context *fc) +{ + if (!init_pseudo(fc, RINGBUFFER_FS_MAGIC)) + return -ENOMEM; + fc->s_iflags |= SB_I_NOEXEC; + return 0; +} + +static int __init ringbuffer_setup(void) +{ + static struct file_system_type ringbuffer_fs = { + .name = "ringbuffer", + .init_fs_context = ringbuffer_init_fs_context, + .kill_sb = kill_anon_super, + }; + ringbuffer_mnt = kern_mount(&ringbuffer_fs); + if (IS_ERR(ringbuffer_mnt)) + panic("Failed to create ringbuffer fs mount."); + return 0; +} +__initcall(ringbuffer_setup); diff --git a/include/linux/fs.h b/include/linux/fs.h index 0283cf366c2a..ba30fdfff5cb 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -978,6 +978,8 @@ static inline int ra_has_index(struct file_ra_state *ra, pgoff_t index) index < ra->start + ra->size); } +struct ringbuffer; + /* * f_{lock,count,pos_lock} members can be highly contended and share * the same cacheline. f_{lock,mode} are very frequently used together @@ -1024,6 +1026,14 @@ struct file { struct address_space *f_mapping; errseq_t f_wb_err; errseq_t f_sb_err; /* for syncfs */ + +#ifdef CONFIG_RINGBUFFER + /* + * Ringbuffers for reading/writing without syncall overhead, created by + * ringbuffer(2) + */ + struct ringbuffer *f_ringbuffers[2]; +#endif } __randomize_layout __attribute__((aligned(4))); /* lest something weird decides that 2 is OK */ @@ -2051,6 +2061,10 @@ struct file_operations { #define FOP_DIO_PARALLEL_WRITE ((__force fop_flags_t)(1 << 3)) /* Contains huge pages */ #define FOP_HUGE_PAGES ((__force fop_flags_t)(1 << 4)) +/* Supports read ringbuffers */ +#define FOP_RINGBUFFER_READ ((__force fop_flags_t)(1 << 5)) +/* Supports write ringbuffers */ +#define FOP_RINGBUFFER_WRITE ((__force fop_flags_t)(1 << 6)) /* Wrap a directory iterator that needs exclusive inode access */ int wrap_directory_iterator(struct file *, struct dir_context *, diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 24323c7d0bd4..6e412718ce7e 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -5,6 +5,7 @@ #include #include +#include #include #include #include @@ -911,6 +912,9 @@ struct mm_struct { spinlock_t ioctx_lock; struct kioctx_table __rcu *ioctx_table; #endif +#ifdef CONFIG_RINGBUFFER + DARRAY(struct ringbuffer *) ringbuffers; +#endif #ifdef CONFIG_MEMCG /* * "owner" points to a task that is regarded as the canonical diff --git a/include/linux/ringbuffer_sys.h b/include/linux/ringbuffer_sys.h new file mode 100644 index 000000000000..e9b3d0a0910f --- /dev/null +++ b/include/linux/ringbuffer_sys.h @@ -0,0 +1,15 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_RINGBUFFER_SYS_H +#define _LINUX_RINGBUFFER_SYS_H + +struct file; +void ringbuffer_file_exit(struct file *file); + +struct mm_struct; +void ringbuffer_mm_exit(struct mm_struct *mm); + +struct ringbuffer; +size_t ringbuffer_read(struct ringbuffer *rb, void *data, size_t len, bool nonblocking); +size_t ringbuffer_write(struct ringbuffer *rb, void *data, size_t len, bool nonblocking); + +#endif /* _LINUX_RINGBUFFER_SYS_H */ diff --git a/include/uapi/linux/ringbuffer_sys.h b/include/uapi/linux/ringbuffer_sys.h new file mode 100644 index 000000000000..d7a3af42da91 --- /dev/null +++ b/include/uapi/linux/ringbuffer_sys.h @@ -0,0 +1,38 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef _UAPI_LINUX_RINGBUFFER_SYS_H +#define _UAPI_LINUX_RINGBUFFER_SYS_H + +/* + * ringbuffer_ptrs - head and tail pointers for a ringbuffer, mappped to + * userspace: + */ +struct ringbuffer_ptrs { + /* + * We use u32s because this type is shared between the kernel and + * userspace - ulong/size_t won't work here, we might be 32bit userland + * and 64 bit kernel, and u64 would be preferable (reduced probability + * of ABA) but not all architectures can atomically read/write to a u64; + * we need to avoid torn reads/writes. + * + * head and tail pointers are incremented and stored without masking; + * this is to avoid ABA and differentiate between a full and empty + * buffer - they must be masked with @mask to get an actual offset into + * the data buffer. + * + * All units are in bytes. + * + * Data is emitted at head, consumed from tail. + */ + u32 head; + u32 tail; + u32 size; /* always a power of two */ + u32 mask; /* size - 1 */ + + /* + * Starting offset of data buffer, from the start of this struct - will + * always be PAGE_SIZE. + */ + u32 data_offset; +}; + +#endif /* _UAPI_LINUX_RINGBUFFER_SYS_H */ diff --git a/init/Kconfig b/init/Kconfig index 72404c1f2157..1ff8eaa43e2f 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1673,6 +1673,14 @@ config IO_URING applications to submit and complete IO through submission and completion rings that are shared between the kernel and application. +config RINGBUFFER + bool "Enable ringbuffer() syscall" if EXPERT + default y + help + This option adds support for generic ringbuffers, which can be + attached to any (supported) file descriptor, allowing for reading and + writing without syscall overhead. + config ADVISE_SYSCALLS bool "Enable madvise/fadvise syscalls" if EXPERT default y diff --git a/kernel/fork.c b/kernel/fork.c index 99076dbe27d8..ea160a9abd60 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1340,6 +1340,7 @@ static inline void __mmput(struct mm_struct *mm) VM_BUG_ON(atomic_read(&mm->mm_users)); uprobe_clear_state(mm); + ringbuffer_mm_exit(mm); exit_aio(mm); ksm_exit(mm); khugepaged_exit(mm); /* must run before exit_mmap */