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earth-shaking: - More Chinese translations, and an update to the Italian translations. The Japanese, Korean, and traditional Chinese translations are more-or-less unmaintained at this point, instead. - Some build-system performance improvements. - The removal of the archaic submitting-drivers.rst document, with the movement of what useful material that remained into other docs. - Improvements to sphinx-pre-install to, hopefully, give more useful suggestions. - A number of build-warning fixes Plus the usual collection of typo fixes, updates, and more. -----BEGIN PGP SIGNATURE----- iQFDBAABCAAtFiEEIw+MvkEiF49krdp9F0NaE2wMflgFAmLn9OwPHGNvcmJldEBs d24ubmV0AAoJEBdDWhNsDH5YtrwIAJNZoDYJJIRuVHnFkAn5EJ4b/chnR1dSTBtn WdE/1zdAlMBWVlEGO48VZybph9Sk0v+cUGf+yviDgASQrfOhRRTkg/0u6XaBAYO0 +C2D1QDd9DggGgajxsfJfTdD3IuB78mGmCQvP17XIJW+NK1CK9rXZBnj6WC5/HJw PCHzeeVreBxOS3W9GelMYa6vjVl7dv81x4DPllnsgU2AMk0/Ce0MVjeIZ695sOeP Ki6jZgC2GsgFSK5kBC35OiDe5q+fDzlLfek34EUCn4SIbMALSUYWO1db122w5Pme Ej0+UTBhD19WH1uB/rcVKnVWugi7UEUJexZsao+nC7UrdIVtYq0= =83BG -----END PGP SIGNATURE----- Merge tag 'docs-6.0' of git://git.lwn.net/linux Pull documentation updates from Jonathan Corbet: "This was a moderately busy cycle for documentation, but nothing all that earth-shaking: - More Chinese translations, and an update to the Italian translations. The Japanese, Korean, and traditional Chinese translations are more-or-less unmaintained at this point, instead. - Some build-system performance improvements. - The removal of the archaic submitting-drivers.rst document, with the movement of what useful material that remained into other docs. - Improvements to sphinx-pre-install to, hopefully, give more useful suggestions. - A number of build-warning fixes Plus the usual collection of typo fixes, updates, and more" * tag 'docs-6.0' of git://git.lwn.net/linux: (92 commits) docs: efi-stub: Fix paths for x86 / arm stubs Docs/zh_CN: Update the translation of sched-stats to 5.19-rc8 Docs/zh_CN: Update the translation of pci to 5.19-rc8 Docs/zh_CN: Update the translation of pci-iov-howto to 5.19-rc8 Docs/zh_CN: Update the translation of usage to 5.19-rc8 Docs/zh_CN: Update the translation of testing-overview to 5.19-rc8 Docs/zh_CN: Update the translation of sparse to 5.19-rc8 Docs/zh_CN: Update the translation of kasan to 5.19-rc8 Docs/zh_CN: Update the translation of iio_configfs to 5.19-rc8 doc:it_IT: align Italian documentation docs: Remove spurious tag from admin-guide/mm/overcommit-accounting.rst Documentation: process: Update email client instructions for Thunderbird docs: ABI: correct QEMU fw_cfg spec path doc/zh_CN: remove submitting-driver reference from docs docs: zh_TW: align to submitting-drivers removal docs: zh_CN: align to submitting-drivers removal docs: ko_KR: howto: remove reference to removed submitting-drivers docs: ja_JP: howto: remove reference to removed submitting-drivers docs: it_IT: align to submitting-drivers removal docs: process: remove outdated submitting-drivers.rst ...
700 lines
17 KiB
C
700 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Watch queue and general notification mechanism, built on pipes
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*
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* Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* See Documentation/core-api/watch_queue.rst
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*/
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#define pr_fmt(fmt) "watchq: " fmt
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/printk.h>
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#include <linux/miscdevice.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/pagemap.h>
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#include <linux/poll.h>
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#include <linux/uaccess.h>
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#include <linux/vmalloc.h>
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#include <linux/file.h>
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#include <linux/security.h>
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#include <linux/cred.h>
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#include <linux/sched/signal.h>
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#include <linux/watch_queue.h>
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#include <linux/pipe_fs_i.h>
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MODULE_DESCRIPTION("Watch queue");
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MODULE_AUTHOR("Red Hat, Inc.");
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MODULE_LICENSE("GPL");
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#define WATCH_QUEUE_NOTE_SIZE 128
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#define WATCH_QUEUE_NOTES_PER_PAGE (PAGE_SIZE / WATCH_QUEUE_NOTE_SIZE)
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/*
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* This must be called under the RCU read-lock, which makes
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* sure that the wqueue still exists. It can then take the lock,
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* and check that the wqueue hasn't been destroyed, which in
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* turn makes sure that the notification pipe still exists.
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*/
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static inline bool lock_wqueue(struct watch_queue *wqueue)
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{
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spin_lock_bh(&wqueue->lock);
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if (unlikely(wqueue->defunct)) {
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spin_unlock_bh(&wqueue->lock);
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return false;
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}
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return true;
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}
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static inline void unlock_wqueue(struct watch_queue *wqueue)
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{
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spin_unlock_bh(&wqueue->lock);
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}
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static void watch_queue_pipe_buf_release(struct pipe_inode_info *pipe,
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struct pipe_buffer *buf)
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{
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struct watch_queue *wqueue = (struct watch_queue *)buf->private;
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struct page *page;
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unsigned int bit;
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/* We need to work out which note within the page this refers to, but
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* the note might have been maximum size, so merely ANDing the offset
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* off doesn't work. OTOH, the note must've been more than zero size.
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*/
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bit = buf->offset + buf->len;
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if ((bit & (WATCH_QUEUE_NOTE_SIZE - 1)) == 0)
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bit -= WATCH_QUEUE_NOTE_SIZE;
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bit /= WATCH_QUEUE_NOTE_SIZE;
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page = buf->page;
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bit += page->index;
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set_bit(bit, wqueue->notes_bitmap);
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generic_pipe_buf_release(pipe, buf);
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}
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// No try_steal function => no stealing
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#define watch_queue_pipe_buf_try_steal NULL
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/* New data written to a pipe may be appended to a buffer with this type. */
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static const struct pipe_buf_operations watch_queue_pipe_buf_ops = {
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.release = watch_queue_pipe_buf_release,
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.try_steal = watch_queue_pipe_buf_try_steal,
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.get = generic_pipe_buf_get,
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};
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/*
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* Post a notification to a watch queue.
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*
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* Must be called with the RCU lock for reading, and the
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* watch_queue lock held, which guarantees that the pipe
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* hasn't been released.
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*/
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static bool post_one_notification(struct watch_queue *wqueue,
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struct watch_notification *n)
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{
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void *p;
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struct pipe_inode_info *pipe = wqueue->pipe;
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struct pipe_buffer *buf;
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struct page *page;
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unsigned int head, tail, mask, note, offset, len;
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bool done = false;
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if (!pipe)
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return false;
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spin_lock_irq(&pipe->rd_wait.lock);
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mask = pipe->ring_size - 1;
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head = pipe->head;
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tail = pipe->tail;
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if (pipe_full(head, tail, pipe->ring_size))
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goto lost;
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note = find_first_bit(wqueue->notes_bitmap, wqueue->nr_notes);
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if (note >= wqueue->nr_notes)
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goto lost;
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page = wqueue->notes[note / WATCH_QUEUE_NOTES_PER_PAGE];
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offset = note % WATCH_QUEUE_NOTES_PER_PAGE * WATCH_QUEUE_NOTE_SIZE;
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get_page(page);
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len = n->info & WATCH_INFO_LENGTH;
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p = kmap_atomic(page);
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memcpy(p + offset, n, len);
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kunmap_atomic(p);
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buf = &pipe->bufs[head & mask];
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buf->page = page;
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buf->private = (unsigned long)wqueue;
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buf->ops = &watch_queue_pipe_buf_ops;
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buf->offset = offset;
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buf->len = len;
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buf->flags = PIPE_BUF_FLAG_WHOLE;
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smp_store_release(&pipe->head, head + 1); /* vs pipe_read() */
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if (!test_and_clear_bit(note, wqueue->notes_bitmap)) {
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spin_unlock_irq(&pipe->rd_wait.lock);
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BUG();
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}
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wake_up_interruptible_sync_poll_locked(&pipe->rd_wait, EPOLLIN | EPOLLRDNORM);
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done = true;
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out:
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spin_unlock_irq(&pipe->rd_wait.lock);
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if (done)
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kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
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return done;
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lost:
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buf = &pipe->bufs[(head - 1) & mask];
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buf->flags |= PIPE_BUF_FLAG_LOSS;
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goto out;
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}
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/*
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* Apply filter rules to a notification.
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*/
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static bool filter_watch_notification(const struct watch_filter *wf,
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const struct watch_notification *n)
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{
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const struct watch_type_filter *wt;
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unsigned int st_bits = sizeof(wt->subtype_filter[0]) * 8;
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unsigned int st_index = n->subtype / st_bits;
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unsigned int st_bit = 1U << (n->subtype % st_bits);
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int i;
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if (!test_bit(n->type, wf->type_filter))
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return false;
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for (i = 0; i < wf->nr_filters; i++) {
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wt = &wf->filters[i];
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if (n->type == wt->type &&
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(wt->subtype_filter[st_index] & st_bit) &&
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(n->info & wt->info_mask) == wt->info_filter)
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return true;
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}
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return false; /* If there is a filter, the default is to reject. */
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}
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/**
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* __post_watch_notification - Post an event notification
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* @wlist: The watch list to post the event to.
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* @n: The notification record to post.
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* @cred: The creds of the process that triggered the notification.
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* @id: The ID to match on the watch.
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*
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* Post a notification of an event into a set of watch queues and let the users
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* know.
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*
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* The size of the notification should be set in n->info & WATCH_INFO_LENGTH and
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* should be in units of sizeof(*n).
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*/
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void __post_watch_notification(struct watch_list *wlist,
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struct watch_notification *n,
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const struct cred *cred,
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u64 id)
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{
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const struct watch_filter *wf;
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struct watch_queue *wqueue;
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struct watch *watch;
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if (((n->info & WATCH_INFO_LENGTH) >> WATCH_INFO_LENGTH__SHIFT) == 0) {
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WARN_ON(1);
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return;
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}
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rcu_read_lock();
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hlist_for_each_entry_rcu(watch, &wlist->watchers, list_node) {
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if (watch->id != id)
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continue;
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n->info &= ~WATCH_INFO_ID;
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n->info |= watch->info_id;
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wqueue = rcu_dereference(watch->queue);
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wf = rcu_dereference(wqueue->filter);
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if (wf && !filter_watch_notification(wf, n))
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continue;
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if (security_post_notification(watch->cred, cred, n) < 0)
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continue;
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if (lock_wqueue(wqueue)) {
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post_one_notification(wqueue, n);
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unlock_wqueue(wqueue);
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}
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}
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rcu_read_unlock();
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}
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EXPORT_SYMBOL(__post_watch_notification);
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/*
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* Allocate sufficient pages to preallocation for the requested number of
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* notifications.
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*/
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long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes)
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{
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struct watch_queue *wqueue = pipe->watch_queue;
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struct page **pages;
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unsigned long *bitmap;
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unsigned long user_bufs;
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int ret, i, nr_pages;
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if (!wqueue)
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return -ENODEV;
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if (wqueue->notes)
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return -EBUSY;
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if (nr_notes < 1 ||
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nr_notes > 512) /* TODO: choose a better hard limit */
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return -EINVAL;
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nr_pages = (nr_notes + WATCH_QUEUE_NOTES_PER_PAGE - 1);
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nr_pages /= WATCH_QUEUE_NOTES_PER_PAGE;
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user_bufs = account_pipe_buffers(pipe->user, pipe->nr_accounted, nr_pages);
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if (nr_pages > pipe->max_usage &&
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(too_many_pipe_buffers_hard(user_bufs) ||
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too_many_pipe_buffers_soft(user_bufs)) &&
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pipe_is_unprivileged_user()) {
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ret = -EPERM;
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goto error;
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}
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nr_notes = nr_pages * WATCH_QUEUE_NOTES_PER_PAGE;
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ret = pipe_resize_ring(pipe, roundup_pow_of_two(nr_notes));
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if (ret < 0)
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goto error;
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pages = kcalloc(sizeof(struct page *), nr_pages, GFP_KERNEL);
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if (!pages)
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goto error;
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for (i = 0; i < nr_pages; i++) {
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pages[i] = alloc_page(GFP_KERNEL);
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if (!pages[i])
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goto error_p;
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pages[i]->index = i * WATCH_QUEUE_NOTES_PER_PAGE;
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}
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bitmap = bitmap_alloc(nr_notes, GFP_KERNEL);
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if (!bitmap)
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goto error_p;
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bitmap_fill(bitmap, nr_notes);
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wqueue->notes = pages;
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wqueue->notes_bitmap = bitmap;
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wqueue->nr_pages = nr_pages;
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wqueue->nr_notes = nr_notes;
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return 0;
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error_p:
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while (--i >= 0)
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__free_page(pages[i]);
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kfree(pages);
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error:
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(void) account_pipe_buffers(pipe->user, nr_pages, pipe->nr_accounted);
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return ret;
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}
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/*
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* Set the filter on a watch queue.
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*/
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long watch_queue_set_filter(struct pipe_inode_info *pipe,
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struct watch_notification_filter __user *_filter)
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{
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struct watch_notification_type_filter *tf;
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struct watch_notification_filter filter;
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struct watch_type_filter *q;
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struct watch_filter *wfilter;
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struct watch_queue *wqueue = pipe->watch_queue;
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int ret, nr_filter = 0, i;
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if (!wqueue)
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return -ENODEV;
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if (!_filter) {
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/* Remove the old filter */
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wfilter = NULL;
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goto set;
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}
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/* Grab the user's filter specification */
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if (copy_from_user(&filter, _filter, sizeof(filter)) != 0)
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return -EFAULT;
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if (filter.nr_filters == 0 ||
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filter.nr_filters > 16 ||
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filter.__reserved != 0)
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return -EINVAL;
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tf = memdup_user(_filter->filters, filter.nr_filters * sizeof(*tf));
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if (IS_ERR(tf))
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return PTR_ERR(tf);
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ret = -EINVAL;
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for (i = 0; i < filter.nr_filters; i++) {
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if ((tf[i].info_filter & ~tf[i].info_mask) ||
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tf[i].info_mask & WATCH_INFO_LENGTH)
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goto err_filter;
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/* Ignore any unknown types */
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if (tf[i].type >= WATCH_TYPE__NR)
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continue;
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nr_filter++;
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}
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/* Now we need to build the internal filter from only the relevant
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* user-specified filters.
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*/
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ret = -ENOMEM;
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wfilter = kzalloc(struct_size(wfilter, filters, nr_filter), GFP_KERNEL);
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if (!wfilter)
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goto err_filter;
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wfilter->nr_filters = nr_filter;
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q = wfilter->filters;
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for (i = 0; i < filter.nr_filters; i++) {
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if (tf[i].type >= WATCH_TYPE__NR)
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continue;
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q->type = tf[i].type;
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q->info_filter = tf[i].info_filter;
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q->info_mask = tf[i].info_mask;
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q->subtype_filter[0] = tf[i].subtype_filter[0];
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__set_bit(q->type, wfilter->type_filter);
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q++;
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}
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kfree(tf);
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set:
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pipe_lock(pipe);
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wfilter = rcu_replace_pointer(wqueue->filter, wfilter,
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lockdep_is_held(&pipe->mutex));
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pipe_unlock(pipe);
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if (wfilter)
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kfree_rcu(wfilter, rcu);
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return 0;
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err_filter:
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kfree(tf);
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return ret;
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}
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static void __put_watch_queue(struct kref *kref)
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{
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struct watch_queue *wqueue =
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container_of(kref, struct watch_queue, usage);
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struct watch_filter *wfilter;
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int i;
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for (i = 0; i < wqueue->nr_pages; i++)
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__free_page(wqueue->notes[i]);
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kfree(wqueue->notes);
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bitmap_free(wqueue->notes_bitmap);
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wfilter = rcu_access_pointer(wqueue->filter);
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if (wfilter)
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kfree_rcu(wfilter, rcu);
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kfree_rcu(wqueue, rcu);
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}
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/**
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* put_watch_queue - Dispose of a ref on a watchqueue.
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* @wqueue: The watch queue to unref.
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*/
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void put_watch_queue(struct watch_queue *wqueue)
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{
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kref_put(&wqueue->usage, __put_watch_queue);
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}
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EXPORT_SYMBOL(put_watch_queue);
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static void free_watch(struct rcu_head *rcu)
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{
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struct watch *watch = container_of(rcu, struct watch, rcu);
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put_watch_queue(rcu_access_pointer(watch->queue));
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atomic_dec(&watch->cred->user->nr_watches);
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put_cred(watch->cred);
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kfree(watch);
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}
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static void __put_watch(struct kref *kref)
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{
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struct watch *watch = container_of(kref, struct watch, usage);
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call_rcu(&watch->rcu, free_watch);
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}
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/*
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* Discard a watch.
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*/
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static void put_watch(struct watch *watch)
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{
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kref_put(&watch->usage, __put_watch);
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}
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/**
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* init_watch - Initialise a watch
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* @watch: The watch to initialise.
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* @wqueue: The queue to assign.
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*
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* Initialise a watch and set the watch queue.
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*/
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void init_watch(struct watch *watch, struct watch_queue *wqueue)
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{
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kref_init(&watch->usage);
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INIT_HLIST_NODE(&watch->list_node);
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INIT_HLIST_NODE(&watch->queue_node);
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rcu_assign_pointer(watch->queue, wqueue);
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}
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static int add_one_watch(struct watch *watch, struct watch_list *wlist, struct watch_queue *wqueue)
|
|
{
|
|
const struct cred *cred;
|
|
struct watch *w;
|
|
|
|
hlist_for_each_entry(w, &wlist->watchers, list_node) {
|
|
struct watch_queue *wq = rcu_access_pointer(w->queue);
|
|
if (wqueue == wq && watch->id == w->id)
|
|
return -EBUSY;
|
|
}
|
|
|
|
cred = current_cred();
|
|
if (atomic_inc_return(&cred->user->nr_watches) > task_rlimit(current, RLIMIT_NOFILE)) {
|
|
atomic_dec(&cred->user->nr_watches);
|
|
return -EAGAIN;
|
|
}
|
|
|
|
watch->cred = get_cred(cred);
|
|
rcu_assign_pointer(watch->watch_list, wlist);
|
|
|
|
kref_get(&wqueue->usage);
|
|
kref_get(&watch->usage);
|
|
hlist_add_head(&watch->queue_node, &wqueue->watches);
|
|
hlist_add_head_rcu(&watch->list_node, &wlist->watchers);
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* add_watch_to_object - Add a watch on an object to a watch list
|
|
* @watch: The watch to add
|
|
* @wlist: The watch list to add to
|
|
*
|
|
* @watch->queue must have been set to point to the queue to post notifications
|
|
* to and the watch list of the object to be watched. @watch->cred must also
|
|
* have been set to the appropriate credentials and a ref taken on them.
|
|
*
|
|
* The caller must pin the queue and the list both and must hold the list
|
|
* locked against racing watch additions/removals.
|
|
*/
|
|
int add_watch_to_object(struct watch *watch, struct watch_list *wlist)
|
|
{
|
|
struct watch_queue *wqueue;
|
|
int ret = -ENOENT;
|
|
|
|
rcu_read_lock();
|
|
|
|
wqueue = rcu_access_pointer(watch->queue);
|
|
if (lock_wqueue(wqueue)) {
|
|
spin_lock(&wlist->lock);
|
|
ret = add_one_watch(watch, wlist, wqueue);
|
|
spin_unlock(&wlist->lock);
|
|
unlock_wqueue(wqueue);
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(add_watch_to_object);
|
|
|
|
/**
|
|
* remove_watch_from_object - Remove a watch or all watches from an object.
|
|
* @wlist: The watch list to remove from
|
|
* @wq: The watch queue of interest (ignored if @all is true)
|
|
* @id: The ID of the watch to remove (ignored if @all is true)
|
|
* @all: True to remove all objects
|
|
*
|
|
* Remove a specific watch or all watches from an object. A notification is
|
|
* sent to the watcher to tell them that this happened.
|
|
*/
|
|
int remove_watch_from_object(struct watch_list *wlist, struct watch_queue *wq,
|
|
u64 id, bool all)
|
|
{
|
|
struct watch_notification_removal n;
|
|
struct watch_queue *wqueue;
|
|
struct watch *watch;
|
|
int ret = -EBADSLT;
|
|
|
|
rcu_read_lock();
|
|
|
|
again:
|
|
spin_lock(&wlist->lock);
|
|
hlist_for_each_entry(watch, &wlist->watchers, list_node) {
|
|
if (all ||
|
|
(watch->id == id && rcu_access_pointer(watch->queue) == wq))
|
|
goto found;
|
|
}
|
|
spin_unlock(&wlist->lock);
|
|
goto out;
|
|
|
|
found:
|
|
ret = 0;
|
|
hlist_del_init_rcu(&watch->list_node);
|
|
rcu_assign_pointer(watch->watch_list, NULL);
|
|
spin_unlock(&wlist->lock);
|
|
|
|
/* We now own the reference on watch that used to belong to wlist. */
|
|
|
|
n.watch.type = WATCH_TYPE_META;
|
|
n.watch.subtype = WATCH_META_REMOVAL_NOTIFICATION;
|
|
n.watch.info = watch->info_id | watch_sizeof(n.watch);
|
|
n.id = id;
|
|
if (id != 0)
|
|
n.watch.info = watch->info_id | watch_sizeof(n);
|
|
|
|
wqueue = rcu_dereference(watch->queue);
|
|
|
|
if (lock_wqueue(wqueue)) {
|
|
post_one_notification(wqueue, &n.watch);
|
|
|
|
if (!hlist_unhashed(&watch->queue_node)) {
|
|
hlist_del_init_rcu(&watch->queue_node);
|
|
put_watch(watch);
|
|
}
|
|
|
|
unlock_wqueue(wqueue);
|
|
}
|
|
|
|
if (wlist->release_watch) {
|
|
void (*release_watch)(struct watch *);
|
|
|
|
release_watch = wlist->release_watch;
|
|
rcu_read_unlock();
|
|
(*release_watch)(watch);
|
|
rcu_read_lock();
|
|
}
|
|
put_watch(watch);
|
|
|
|
if (all && !hlist_empty(&wlist->watchers))
|
|
goto again;
|
|
out:
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(remove_watch_from_object);
|
|
|
|
/*
|
|
* Remove all the watches that are contributory to a queue. This has the
|
|
* potential to race with removal of the watches by the destruction of the
|
|
* objects being watched or with the distribution of notifications.
|
|
*/
|
|
void watch_queue_clear(struct watch_queue *wqueue)
|
|
{
|
|
struct watch_list *wlist;
|
|
struct watch *watch;
|
|
bool release;
|
|
|
|
rcu_read_lock();
|
|
spin_lock_bh(&wqueue->lock);
|
|
|
|
/* Prevent new notifications from being stored. */
|
|
wqueue->defunct = true;
|
|
|
|
while (!hlist_empty(&wqueue->watches)) {
|
|
watch = hlist_entry(wqueue->watches.first, struct watch, queue_node);
|
|
hlist_del_init_rcu(&watch->queue_node);
|
|
/* We now own a ref on the watch. */
|
|
spin_unlock_bh(&wqueue->lock);
|
|
|
|
/* We can't do the next bit under the queue lock as we need to
|
|
* get the list lock - which would cause a deadlock if someone
|
|
* was removing from the opposite direction at the same time or
|
|
* posting a notification.
|
|
*/
|
|
wlist = rcu_dereference(watch->watch_list);
|
|
if (wlist) {
|
|
void (*release_watch)(struct watch *);
|
|
|
|
spin_lock(&wlist->lock);
|
|
|
|
release = !hlist_unhashed(&watch->list_node);
|
|
if (release) {
|
|
hlist_del_init_rcu(&watch->list_node);
|
|
rcu_assign_pointer(watch->watch_list, NULL);
|
|
|
|
/* We now own a second ref on the watch. */
|
|
}
|
|
|
|
release_watch = wlist->release_watch;
|
|
spin_unlock(&wlist->lock);
|
|
|
|
if (release) {
|
|
if (release_watch) {
|
|
rcu_read_unlock();
|
|
/* This might need to call dput(), so
|
|
* we have to drop all the locks.
|
|
*/
|
|
(*release_watch)(watch);
|
|
rcu_read_lock();
|
|
}
|
|
put_watch(watch);
|
|
}
|
|
}
|
|
|
|
put_watch(watch);
|
|
spin_lock_bh(&wqueue->lock);
|
|
}
|
|
|
|
spin_unlock_bh(&wqueue->lock);
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/**
|
|
* get_watch_queue - Get a watch queue from its file descriptor.
|
|
* @fd: The fd to query.
|
|
*/
|
|
struct watch_queue *get_watch_queue(int fd)
|
|
{
|
|
struct pipe_inode_info *pipe;
|
|
struct watch_queue *wqueue = ERR_PTR(-EINVAL);
|
|
struct fd f;
|
|
|
|
f = fdget(fd);
|
|
if (f.file) {
|
|
pipe = get_pipe_info(f.file, false);
|
|
if (pipe && pipe->watch_queue) {
|
|
wqueue = pipe->watch_queue;
|
|
kref_get(&wqueue->usage);
|
|
}
|
|
fdput(f);
|
|
}
|
|
|
|
return wqueue;
|
|
}
|
|
EXPORT_SYMBOL(get_watch_queue);
|
|
|
|
/*
|
|
* Initialise a watch queue
|
|
*/
|
|
int watch_queue_init(struct pipe_inode_info *pipe)
|
|
{
|
|
struct watch_queue *wqueue;
|
|
|
|
wqueue = kzalloc(sizeof(*wqueue), GFP_KERNEL);
|
|
if (!wqueue)
|
|
return -ENOMEM;
|
|
|
|
wqueue->pipe = pipe;
|
|
kref_init(&wqueue->usage);
|
|
spin_lock_init(&wqueue->lock);
|
|
INIT_HLIST_HEAD(&wqueue->watches);
|
|
|
|
pipe->watch_queue = wqueue;
|
|
return 0;
|
|
}
|