cachefiles: Register a miscdev and parse commands over it
Register a misc device with which to talk to the daemon. The misc device holds a cache set up through it around and closing the device kills the cache. cachefilesd communicates with the kernel by passing it single-line text commands. Parse these and use them to parameterise the cache state. This does not implement the command to actually bring a cache online. That's left for later. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/163819628388.215744.17712097043607299608.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906929128.143852.14065207858943654011.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967139085.1823006.3514846391807454287.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021538400.640689.9172006906288062041.stgit@warthog.procyon.org.uk/ # v4
This commit is contained in:
David Howells
parent
254947d479
commit
8667d434b2
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@ -4,6 +4,7 @@
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#
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cachefiles-y := \
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daemon.o \
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main.o \
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security.o
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@ -0,0 +1,725 @@
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// SPDX-License-Identifier: GPL-2.0-or-later
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/* Daemon interface
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*
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* Copyright (C) 2007, 2021 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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#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/completion.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/file.h>
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#include <linux/namei.h>
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#include <linux/poll.h>
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#include <linux/mount.h>
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#include <linux/statfs.h>
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#include <linux/ctype.h>
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#include <linux/string.h>
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#include <linux/fs_struct.h>
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#include "internal.h"
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static int cachefiles_daemon_open(struct inode *, struct file *);
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static int cachefiles_daemon_release(struct inode *, struct file *);
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static ssize_t cachefiles_daemon_read(struct file *, char __user *, size_t,
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loff_t *);
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static ssize_t cachefiles_daemon_write(struct file *, const char __user *,
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size_t, loff_t *);
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static __poll_t cachefiles_daemon_poll(struct file *,
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struct poll_table_struct *);
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static int cachefiles_daemon_frun(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_fcull(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_fstop(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_brun(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_bcull(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_bstop(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_cull(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_debug(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_dir(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_inuse(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_secctx(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_tag(struct cachefiles_cache *, char *);
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static int cachefiles_daemon_bind(struct cachefiles_cache *, char *);
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static void cachefiles_daemon_unbind(struct cachefiles_cache *);
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static unsigned long cachefiles_open;
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const struct file_operations cachefiles_daemon_fops = {
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.owner = THIS_MODULE,
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.open = cachefiles_daemon_open,
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.release = cachefiles_daemon_release,
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.read = cachefiles_daemon_read,
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.write = cachefiles_daemon_write,
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.poll = cachefiles_daemon_poll,
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.llseek = noop_llseek,
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};
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struct cachefiles_daemon_cmd {
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char name[8];
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int (*handler)(struct cachefiles_cache *cache, char *args);
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};
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static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
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{ "bind", cachefiles_daemon_bind },
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{ "brun", cachefiles_daemon_brun },
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{ "bcull", cachefiles_daemon_bcull },
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{ "bstop", cachefiles_daemon_bstop },
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{ "cull", cachefiles_daemon_cull },
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{ "debug", cachefiles_daemon_debug },
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{ "dir", cachefiles_daemon_dir },
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{ "frun", cachefiles_daemon_frun },
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{ "fcull", cachefiles_daemon_fcull },
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{ "fstop", cachefiles_daemon_fstop },
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{ "inuse", cachefiles_daemon_inuse },
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{ "secctx", cachefiles_daemon_secctx },
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{ "tag", cachefiles_daemon_tag },
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{ "", NULL }
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};
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/*
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* Prepare a cache for caching.
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*/
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static int cachefiles_daemon_open(struct inode *inode, struct file *file)
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{
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struct cachefiles_cache *cache;
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_enter("");
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/* only the superuser may do this */
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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/* the cachefiles device may only be open once at a time */
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if (xchg(&cachefiles_open, 1) == 1)
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return -EBUSY;
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/* allocate a cache record */
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cache = kzalloc(sizeof(struct cachefiles_cache), GFP_KERNEL);
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if (!cache) {
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cachefiles_open = 0;
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return -ENOMEM;
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}
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mutex_init(&cache->daemon_mutex);
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init_waitqueue_head(&cache->daemon_pollwq);
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/* set default caching limits
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* - limit at 1% free space and/or free files
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* - cull below 5% free space and/or free files
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* - cease culling above 7% free space and/or free files
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*/
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cache->frun_percent = 7;
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cache->fcull_percent = 5;
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cache->fstop_percent = 1;
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cache->brun_percent = 7;
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cache->bcull_percent = 5;
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cache->bstop_percent = 1;
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file->private_data = cache;
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cache->cachefilesd = file;
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return 0;
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}
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/*
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* Release a cache.
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*/
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static int cachefiles_daemon_release(struct inode *inode, struct file *file)
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{
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struct cachefiles_cache *cache = file->private_data;
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_enter("");
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ASSERT(cache);
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set_bit(CACHEFILES_DEAD, &cache->flags);
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cachefiles_daemon_unbind(cache);
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/* clean up the control file interface */
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cache->cachefilesd = NULL;
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file->private_data = NULL;
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cachefiles_open = 0;
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kfree(cache);
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_leave("");
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return 0;
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}
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/*
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* Read the cache state.
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*/
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static ssize_t cachefiles_daemon_read(struct file *file, char __user *_buffer,
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size_t buflen, loff_t *pos)
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{
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struct cachefiles_cache *cache = file->private_data;
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unsigned long long b_released;
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unsigned f_released;
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char buffer[256];
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int n;
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//_enter(",,%zu,", buflen);
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if (!test_bit(CACHEFILES_READY, &cache->flags))
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return 0;
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/* check how much space the cache has */
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// PLACEHOLDER: Check space
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/* summarise */
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f_released = atomic_xchg(&cache->f_released, 0);
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b_released = atomic_long_xchg(&cache->b_released, 0);
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clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
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n = snprintf(buffer, sizeof(buffer),
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"cull=%c"
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" frun=%llx"
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" fcull=%llx"
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" fstop=%llx"
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" brun=%llx"
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" bcull=%llx"
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" bstop=%llx"
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" freleased=%x"
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" breleased=%llx",
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test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
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(unsigned long long) cache->frun,
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(unsigned long long) cache->fcull,
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(unsigned long long) cache->fstop,
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(unsigned long long) cache->brun,
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(unsigned long long) cache->bcull,
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(unsigned long long) cache->bstop,
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f_released,
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b_released);
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if (n > buflen)
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return -EMSGSIZE;
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if (copy_to_user(_buffer, buffer, n) != 0)
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return -EFAULT;
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return n;
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}
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/*
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* Take a command from cachefilesd, parse it and act on it.
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*/
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static ssize_t cachefiles_daemon_write(struct file *file,
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const char __user *_data,
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size_t datalen,
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loff_t *pos)
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{
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const struct cachefiles_daemon_cmd *cmd;
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struct cachefiles_cache *cache = file->private_data;
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ssize_t ret;
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char *data, *args, *cp;
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//_enter(",,%zu,", datalen);
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ASSERT(cache);
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if (test_bit(CACHEFILES_DEAD, &cache->flags))
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return -EIO;
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if (datalen > PAGE_SIZE - 1)
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return -EOPNOTSUPP;
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/* drag the command string into the kernel so we can parse it */
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data = memdup_user_nul(_data, datalen);
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if (IS_ERR(data))
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return PTR_ERR(data);
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ret = -EINVAL;
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if (memchr(data, '\0', datalen))
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goto error;
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/* strip any newline */
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cp = memchr(data, '\n', datalen);
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if (cp) {
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if (cp == data)
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goto error;
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*cp = '\0';
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}
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/* parse the command */
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ret = -EOPNOTSUPP;
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for (args = data; *args; args++)
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if (isspace(*args))
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break;
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if (*args) {
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if (args == data)
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goto error;
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*args = '\0';
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args = skip_spaces(++args);
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}
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/* run the appropriate command handler */
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for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
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if (strcmp(cmd->name, data) == 0)
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goto found_command;
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error:
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kfree(data);
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//_leave(" = %zd", ret);
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return ret;
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found_command:
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mutex_lock(&cache->daemon_mutex);
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ret = -EIO;
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if (!test_bit(CACHEFILES_DEAD, &cache->flags))
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ret = cmd->handler(cache, args);
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mutex_unlock(&cache->daemon_mutex);
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if (ret == 0)
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ret = datalen;
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goto error;
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}
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/*
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* Poll for culling state
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* - use EPOLLOUT to indicate culling state
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*/
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static __poll_t cachefiles_daemon_poll(struct file *file,
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struct poll_table_struct *poll)
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{
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struct cachefiles_cache *cache = file->private_data;
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__poll_t mask;
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poll_wait(file, &cache->daemon_pollwq, poll);
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mask = 0;
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if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
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mask |= EPOLLIN;
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if (test_bit(CACHEFILES_CULLING, &cache->flags))
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mask |= EPOLLOUT;
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return mask;
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}
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/*
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* Give a range error for cache space constraints
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* - can be tail-called
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*/
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static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
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char *args)
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{
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pr_err("Free space limits must be in range 0%%<=stop<cull<run<100%%\n");
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return -EINVAL;
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}
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/*
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* Set the percentage of files at which to stop culling
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* - command: "frun <N>%"
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*/
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static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
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{
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unsigned long frun;
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_enter(",%s", args);
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if (!*args)
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return -EINVAL;
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frun = simple_strtoul(args, &args, 10);
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if (args[0] != '%' || args[1] != '\0')
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return -EINVAL;
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if (frun <= cache->fcull_percent || frun >= 100)
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return cachefiles_daemon_range_error(cache, args);
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cache->frun_percent = frun;
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return 0;
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}
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/*
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* Set the percentage of files at which to start culling
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* - command: "fcull <N>%"
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*/
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static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
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{
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unsigned long fcull;
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_enter(",%s", args);
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if (!*args)
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return -EINVAL;
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fcull = simple_strtoul(args, &args, 10);
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if (args[0] != '%' || args[1] != '\0')
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return -EINVAL;
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if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
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return cachefiles_daemon_range_error(cache, args);
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cache->fcull_percent = fcull;
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return 0;
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}
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/*
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* Set the percentage of files at which to stop allocating
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* - command: "fstop <N>%"
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*/
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static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
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{
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unsigned long fstop;
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_enter(",%s", args);
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if (!*args)
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return -EINVAL;
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fstop = simple_strtoul(args, &args, 10);
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if (args[0] != '%' || args[1] != '\0')
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return -EINVAL;
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if (fstop >= cache->fcull_percent)
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return cachefiles_daemon_range_error(cache, args);
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cache->fstop_percent = fstop;
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return 0;
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}
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/*
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* Set the percentage of blocks at which to stop culling
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* - command: "brun <N>%"
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*/
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static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
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{
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unsigned long brun;
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_enter(",%s", args);
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if (!*args)
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return -EINVAL;
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brun = simple_strtoul(args, &args, 10);
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if (args[0] != '%' || args[1] != '\0')
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return -EINVAL;
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if (brun <= cache->bcull_percent || brun >= 100)
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return cachefiles_daemon_range_error(cache, args);
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cache->brun_percent = brun;
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return 0;
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}
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/*
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* Set the percentage of blocks at which to start culling
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* - command: "bcull <N>%"
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*/
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static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
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{
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unsigned long bcull;
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_enter(",%s", args);
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if (!*args)
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return -EINVAL;
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bcull = simple_strtoul(args, &args, 10);
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if (args[0] != '%' || args[1] != '\0')
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return -EINVAL;
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if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
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return cachefiles_daemon_range_error(cache, args);
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cache->bcull_percent = bcull;
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return 0;
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}
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/*
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* Set the percentage of blocks at which to stop allocating
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* - command: "bstop <N>%"
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*/
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static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
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{
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unsigned long bstop;
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_enter(",%s", args);
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if (!*args)
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return -EINVAL;
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bstop = simple_strtoul(args, &args, 10);
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if (args[0] != '%' || args[1] != '\0')
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return -EINVAL;
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if (bstop >= cache->bcull_percent)
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return cachefiles_daemon_range_error(cache, args);
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|
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cache->bstop_percent = bstop;
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return 0;
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}
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||||
|
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/*
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* Set the cache directory
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||||
* - command: "dir <name>"
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||||
*/
|
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static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
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{
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char *dir;
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_enter(",%s", args);
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if (!*args) {
|
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pr_err("Empty directory specified\n");
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return -EINVAL;
|
||||
}
|
||||
|
||||
if (cache->rootdirname) {
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pr_err("Second cache directory specified\n");
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return -EEXIST;
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}
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|
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dir = kstrdup(args, GFP_KERNEL);
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if (!dir)
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return -ENOMEM;
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|
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cache->rootdirname = dir;
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||||
return 0;
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||||
}
|
||||
|
||||
/*
|
||||
* Set the cache security context
|
||||
* - command: "secctx <ctx>"
|
||||
*/
|
||||
static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args)
|
||||
{
|
||||
char *secctx;
|
||||
|
||||
_enter(",%s", args);
|
||||
|
||||
if (!*args) {
|
||||
pr_err("Empty security context specified\n");
|
||||
return -EINVAL;
|
||||
}
|
||||
|
||||
if (cache->secctx) {
|
||||
pr_err("Second security context specified\n");
|
||||
return -EINVAL;
|
||||
}
|
||||
|
||||
secctx = kstrdup(args, GFP_KERNEL);
|
||||
if (!secctx)
|
||||
return -ENOMEM;
|
||||
|
||||
cache->secctx = secctx;
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Set the cache tag
|
||||
* - command: "tag <name>"
|
||||
*/
|
||||
static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
|
||||
{
|
||||
char *tag;
|
||||
|
||||
_enter(",%s", args);
|
||||
|
||||
if (!*args) {
|
||||
pr_err("Empty tag specified\n");
|
||||
return -EINVAL;
|
||||
}
|
||||
|
||||
if (cache->tag)
|
||||
return -EEXIST;
|
||||
|
||||
tag = kstrdup(args, GFP_KERNEL);
|
||||
if (!tag)
|
||||
return -ENOMEM;
|
||||
|
||||
cache->tag = tag;
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Request a node in the cache be culled from the current working directory
|
||||
* - command: "cull <name>"
|
||||
*/
|
||||
static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
|
||||
{
|
||||
struct path path;
|
||||
const struct cred *saved_cred;
|
||||
int ret;
|
||||
|
||||
_enter(",%s", args);
|
||||
|
||||
if (strchr(args, '/'))
|
||||
goto inval;
|
||||
|
||||
if (!test_bit(CACHEFILES_READY, &cache->flags)) {
|
||||
pr_err("cull applied to unready cache\n");
|
||||
return -EIO;
|
||||
}
|
||||
|
||||
if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
|
||||
pr_err("cull applied to dead cache\n");
|
||||
return -EIO;
|
||||
}
|
||||
|
||||
get_fs_pwd(current->fs, &path);
|
||||
|
||||
if (!d_can_lookup(path.dentry))
|
||||
goto notdir;
|
||||
|
||||
cachefiles_begin_secure(cache, &saved_cred);
|
||||
ret = -ENOANO; // PLACEHOLDER: Do culling
|
||||
cachefiles_end_secure(cache, saved_cred);
|
||||
|
||||
path_put(&path);
|
||||
_leave(" = %d", ret);
|
||||
return ret;
|
||||
|
||||
notdir:
|
||||
path_put(&path);
|
||||
pr_err("cull command requires dirfd to be a directory\n");
|
||||
return -ENOTDIR;
|
||||
|
||||
inval:
|
||||
pr_err("cull command requires dirfd and filename\n");
|
||||
return -EINVAL;
|
||||
}
|
||||
|
||||
/*
|
||||
* Set debugging mode
|
||||
* - command: "debug <mask>"
|
||||
*/
|
||||
static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
|
||||
{
|
||||
unsigned long mask;
|
||||
|
||||
_enter(",%s", args);
|
||||
|
||||
mask = simple_strtoul(args, &args, 0);
|
||||
if (args[0] != '\0')
|
||||
goto inval;
|
||||
|
||||
cachefiles_debug = mask;
|
||||
_leave(" = 0");
|
||||
return 0;
|
||||
|
||||
inval:
|
||||
pr_err("debug command requires mask\n");
|
||||
return -EINVAL;
|
||||
}
|
||||
|
||||
/*
|
||||
* Find out whether an object in the current working directory is in use or not
|
||||
* - command: "inuse <name>"
|
||||
*/
|
||||
static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
|
||||
{
|
||||
struct path path;
|
||||
const struct cred *saved_cred;
|
||||
int ret;
|
||||
|
||||
//_enter(",%s", args);
|
||||
|
||||
if (strchr(args, '/'))
|
||||
goto inval;
|
||||
|
||||
if (!test_bit(CACHEFILES_READY, &cache->flags)) {
|
||||
pr_err("inuse applied to unready cache\n");
|
||||
return -EIO;
|
||||
}
|
||||
|
||||
if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
|
||||
pr_err("inuse applied to dead cache\n");
|
||||
return -EIO;
|
||||
}
|
||||
|
||||
get_fs_pwd(current->fs, &path);
|
||||
|
||||
if (!d_can_lookup(path.dentry))
|
||||
goto notdir;
|
||||
|
||||
cachefiles_begin_secure(cache, &saved_cred);
|
||||
ret = -ENOANO; // PLACEHOLDER: Check if in use
|
||||
cachefiles_end_secure(cache, saved_cred);
|
||||
|
||||
path_put(&path);
|
||||
//_leave(" = %d", ret);
|
||||
return ret;
|
||||
|
||||
notdir:
|
||||
path_put(&path);
|
||||
pr_err("inuse command requires dirfd to be a directory\n");
|
||||
return -ENOTDIR;
|
||||
|
||||
inval:
|
||||
pr_err("inuse command requires dirfd and filename\n");
|
||||
return -EINVAL;
|
||||
}
|
||||
|
||||
/*
|
||||
* Bind a directory as a cache
|
||||
*/
|
||||
static int cachefiles_daemon_bind(struct cachefiles_cache *cache, char *args)
|
||||
{
|
||||
_enter("{%u,%u,%u,%u,%u,%u},%s",
|
||||
cache->frun_percent,
|
||||
cache->fcull_percent,
|
||||
cache->fstop_percent,
|
||||
cache->brun_percent,
|
||||
cache->bcull_percent,
|
||||
cache->bstop_percent,
|
||||
args);
|
||||
|
||||
if (cache->fstop_percent >= cache->fcull_percent ||
|
||||
cache->fcull_percent >= cache->frun_percent ||
|
||||
cache->frun_percent >= 100)
|
||||
return -ERANGE;
|
||||
|
||||
if (cache->bstop_percent >= cache->bcull_percent ||
|
||||
cache->bcull_percent >= cache->brun_percent ||
|
||||
cache->brun_percent >= 100)
|
||||
return -ERANGE;
|
||||
|
||||
if (*args) {
|
||||
pr_err("'bind' command doesn't take an argument\n");
|
||||
return -EINVAL;
|
||||
}
|
||||
|
||||
if (!cache->rootdirname) {
|
||||
pr_err("No cache directory specified\n");
|
||||
return -EINVAL;
|
||||
}
|
||||
|
||||
/* Don't permit already bound caches to be re-bound */
|
||||
if (test_bit(CACHEFILES_READY, &cache->flags)) {
|
||||
pr_err("Cache already bound\n");
|
||||
return -EBUSY;
|
||||
}
|
||||
|
||||
pr_warn("Cache is disabled for development\n");
|
||||
return -ENOANO; // Don't allow the cache to operate yet
|
||||
}
|
||||
|
||||
/*
|
||||
* Unbind a cache.
|
||||
*/
|
||||
static void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
|
||||
{
|
||||
_enter("");
|
||||
|
||||
if (test_bit(CACHEFILES_READY, &cache->flags)) {
|
||||
// PLACEHOLDER: Withdraw cache
|
||||
}
|
||||
|
||||
mntput(cache->mnt);
|
||||
|
||||
kfree(cache->rootdirname);
|
||||
kfree(cache->secctx);
|
||||
kfree(cache->tag);
|
||||
|
||||
_leave("");
|
||||
}
|
||||
|
|
@ -65,6 +65,20 @@ struct cachefiles_cache {
|
|||
|
||||
#include <trace/events/cachefiles.h>
|
||||
|
||||
/*
|
||||
* note change of state for daemon
|
||||
*/
|
||||
static inline void cachefiles_state_changed(struct cachefiles_cache *cache)
|
||||
{
|
||||
set_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
|
||||
wake_up_all(&cache->daemon_pollwq);
|
||||
}
|
||||
|
||||
/*
|
||||
* daemon.c
|
||||
*/
|
||||
extern const struct file_operations cachefiles_daemon_fops;
|
||||
|
||||
/*
|
||||
* error_inject.c
|
||||
*/
|
||||
|
|
|
|||
|
|
@ -31,6 +31,12 @@ MODULE_DESCRIPTION("Mounted-filesystem based cache");
|
|||
MODULE_AUTHOR("Red Hat, Inc.");
|
||||
MODULE_LICENSE("GPL");
|
||||
|
||||
static struct miscdevice cachefiles_dev = {
|
||||
.minor = MISC_DYNAMIC_MINOR,
|
||||
.name = "cachefiles",
|
||||
.fops = &cachefiles_daemon_fops,
|
||||
};
|
||||
|
||||
/*
|
||||
* initialise the fs caching module
|
||||
*/
|
||||
|
|
@ -41,10 +47,15 @@ static int __init cachefiles_init(void)
|
|||
ret = cachefiles_register_error_injection();
|
||||
if (ret < 0)
|
||||
goto error_einj;
|
||||
ret = misc_register(&cachefiles_dev);
|
||||
if (ret < 0)
|
||||
goto error_dev;
|
||||
|
||||
pr_info("Loaded\n");
|
||||
return 0;
|
||||
|
||||
error_dev:
|
||||
cachefiles_unregister_error_injection();
|
||||
error_einj:
|
||||
pr_err("failed to register: %d\n", ret);
|
||||
return ret;
|
||||
|
|
@ -59,6 +70,7 @@ static void __exit cachefiles_exit(void)
|
|||
{
|
||||
pr_info("Unloading\n");
|
||||
|
||||
misc_deregister(&cachefiles_dev);
|
||||
cachefiles_unregister_error_injection();
|
||||
}
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue