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@xxxxxxxxxx>
---
fs/cachefiles/Makefile | 1
fs/cachefiles/daemon.c | 725 ++++++++++++++++++++++++++++++++++++++++++++++
fs/cachefiles/internal.h | 14 +
fs/cachefiles/main.c | 12 +
4 files changed, 752 insertions(+)
create mode 100644 fs/cachefiles/daemon.c
diff --git a/fs/cachefiles/Makefile b/fs/cachefiles/Makefile
index 28bbb0d14868..f008524bb78f 100644
--- a/fs/cachefiles/Makefile
+++ b/fs/cachefiles/Makefile
@@ -4,6 +4,7 @@
#
cachefiles-y := \
+ daemon.o \
main.o \
security.o
diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
new file mode 100644
index 000000000000..4cfb7c8b37d0
--- /dev/null
+++ b/fs/cachefiles/daemon.c
@@ -0,0 +1,725 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Daemon interface
+ *
+ * Copyright (C) 2007, 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/completion.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/namei.h>
+#include <linux/poll.h>
+#include <linux/mount.h>
+#include <linux/statfs.h>
+#include <linux/ctype.h>
+#include <linux/string.h>
+#include <linux/fs_struct.h>
+#include "internal.h"
+
+static int cachefiles_daemon_open(struct inode *, struct file *);
+static int cachefiles_daemon_release(struct inode *, struct file *);
+static ssize_t cachefiles_daemon_read(struct file *, char __user *, size_t,
+ loff_t *);
+static ssize_t cachefiles_daemon_write(struct file *, const char __user *,
+ size_t, loff_t *);
+static __poll_t cachefiles_daemon_poll(struct file *,
+ struct poll_table_struct *);
+static int cachefiles_daemon_frun(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_fcull(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_fstop(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_brun(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_bcull(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_bstop(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_cull(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_debug(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_dir(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_inuse(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_secctx(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_tag(struct cachefiles_cache *, char *);
+static int cachefiles_daemon_bind(struct cachefiles_cache *, char *);
+static void cachefiles_daemon_unbind(struct cachefiles_cache *);
+
+static unsigned long cachefiles_open;
+
+const struct file_operations cachefiles_daemon_fops = {
+ .owner = THIS_MODULE,
+ .open = cachefiles_daemon_open,
+ .release = cachefiles_daemon_release,
+ .read = cachefiles_daemon_read,
+ .write = cachefiles_daemon_write,
+ .poll = cachefiles_daemon_poll,
+ .llseek = noop_llseek,
+};
+
+struct cachefiles_daemon_cmd {
+ char name[8];
+ int (*handler)(struct cachefiles_cache *cache, char *args);
+};
+
+static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
+ { "bind", cachefiles_daemon_bind },
+ { "brun", cachefiles_daemon_brun },
+ { "bcull", cachefiles_daemon_bcull },
+ { "bstop", cachefiles_daemon_bstop },
+ { "cull", cachefiles_daemon_cull },
+ { "debug", cachefiles_daemon_debug },
+ { "dir", cachefiles_daemon_dir },
+ { "frun", cachefiles_daemon_frun },
+ { "fcull", cachefiles_daemon_fcull },
+ { "fstop", cachefiles_daemon_fstop },
+ { "inuse", cachefiles_daemon_inuse },
+ { "secctx", cachefiles_daemon_secctx },
+ { "tag", cachefiles_daemon_tag },
+ { "", NULL }
+};
+
+
+/*
+ * Prepare a cache for caching.
+ */
+static int cachefiles_daemon_open(struct inode *inode, struct file *file)
+{
+ struct cachefiles_cache *cache;
+
+ _enter("");
+
+ /* only the superuser may do this */
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ /* the cachefiles device may only be open once at a time */
+ if (xchg(&cachefiles_open, 1) == 1)
+ return -EBUSY;
+
+ /* allocate a cache record */
+ cache = kzalloc(sizeof(struct cachefiles_cache), GFP_KERNEL);
+ if (!cache) {
+ cachefiles_open = 0;
+ return -ENOMEM;
+ }
+
+ mutex_init(&cache->daemon_mutex);
+ init_waitqueue_head(&cache->daemon_pollwq);
+
+ /* set default caching limits
+ * - limit at 1% free space and/or free files
+ * - cull below 5% free space and/or free files
+ * - cease culling above 7% free space and/or free files
+ */
+ cache->frun_percent = 7;
+ cache->fcull_percent = 5;
+ cache->fstop_percent = 1;
+ cache->brun_percent = 7;
+ cache->bcull_percent = 5;
+ cache->bstop_percent = 1;
+
+ file->private_data = cache;
+ cache->cachefilesd = file;
+ return 0;
+}
+
+/*
+ * Release a cache.
+ */
+static int cachefiles_daemon_release(struct inode *inode, struct file *file)
+{
+ struct cachefiles_cache *cache = file->private_data;
+
+ _enter("");
+
+ ASSERT(cache);
+
+ set_bit(CACHEFILES_DEAD, &cache->flags);
+
+ cachefiles_daemon_unbind(cache);
+
+ /* clean up the control file interface */
+ cache->cachefilesd = NULL;
+ file->private_data = NULL;
+ cachefiles_open = 0;
+
+ kfree(cache);
+
+ _leave("");
+ return 0;
+}
+
+/*
+ * Read the cache state.
+ */
+static ssize_t cachefiles_daemon_read(struct file *file, char __user *_buffer,
+ size_t buflen, loff_t *pos)
+{
+ struct cachefiles_cache *cache = file->private_data;
+ unsigned long long b_released;
+ unsigned f_released;
+ char buffer[256];
+ int n;
+
+ //_enter(",,%zu,", buflen);
+
+ if (!test_bit(CACHEFILES_READY, &cache->flags))
+ return 0;
+
+ /* check how much space the cache has */
+ // PLACEHOLDER: Check space
+
+ /* summarise */
+ f_released = atomic_xchg(&cache->f_released, 0);
+ b_released = atomic_long_xchg(&cache->b_released, 0);
+ clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
+
+ n = snprintf(buffer, sizeof(buffer),
+ "cull=%c"
+ " frun=%llx"
+ " fcull=%llx"
+ " fstop=%llx"
+ " brun=%llx"
+ " bcull=%llx"
+ " bstop=%llx"
+ " freleased=%x"
+ " breleased=%llx",
+ test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
+ (unsigned long long) cache->frun,
+ (unsigned long long) cache->fcull,
+ (unsigned long long) cache->fstop,
+ (unsigned long long) cache->brun,
+ (unsigned long long) cache->bcull,
+ (unsigned long long) cache->bstop,
+ f_released,
+ b_released);
+
+ if (n > buflen)
+ return -EMSGSIZE;
+
+ if (copy_to_user(_buffer, buffer, n) != 0)
+ return -EFAULT;
+
+ return n;
+}
+
+/*
+ * Take a command from cachefilesd, parse it and act on it.
+ */
+static ssize_t cachefiles_daemon_write(struct file *file,
+ const char __user *_data,
+ size_t datalen,
+ loff_t *pos)
+{
+ const struct cachefiles_daemon_cmd *cmd;
+ struct cachefiles_cache *cache = file->private_data;
+ ssize_t ret;
+ char *data, *args, *cp;
+
+ //_enter(",,%zu,", datalen);
+
+ ASSERT(cache);
+
+ if (test_bit(CACHEFILES_DEAD, &cache->flags))
+ return -EIO;
+
+ if (datalen > PAGE_SIZE - 1)
+ return -EOPNOTSUPP;
+
+ /* drag the command string into the kernel so we can parse it */
+ data = memdup_user_nul(_data, datalen);
+ if (IS_ERR(data))
+ return PTR_ERR(data);
+
+ ret = -EINVAL;
+ if (memchr(data, '\0', datalen))
+ goto error;
+
+ /* strip any newline */
+ cp = memchr(data, '\n', datalen);
+ if (cp) {
+ if (cp == data)
+ goto error;
+
+ *cp = '\0';
+ }
+
+ /* parse the command */
+ ret = -EOPNOTSUPP;
+
+ for (args = data; *args; args++)
+ if (isspace(*args))
+ break;
+ if (*args) {
+ if (args == data)
+ goto error;
+ *args = '\0';
+ args = skip_spaces(++args);
+ }
+
+ /* run the appropriate command handler */
+ for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
+ if (strcmp(cmd->name, data) == 0)
+ goto found_command;
+
+error:
+ kfree(data);
+ //_leave(" = %zd", ret);
+ return ret;
+
+found_command:
+ mutex_lock(&cache->daemon_mutex);
+
+ ret = -EIO;
+ if (!test_bit(CACHEFILES_DEAD, &cache->flags))
+ ret = cmd->handler(cache, args);
+
+ mutex_unlock(&cache->daemon_mutex);
+
+ if (ret == 0)
+ ret = datalen;
+ goto error;
+}
+
+/*
+ * Poll for culling state
+ * - use EPOLLOUT to indicate culling state
+ */
+static __poll_t cachefiles_daemon_poll(struct file *file,
+ struct poll_table_struct *poll)
+{
+ struct cachefiles_cache *cache = file->private_data;
+ __poll_t mask;
+
+ poll_wait(file, &cache->daemon_pollwq, poll);
+ mask = 0;
+
+ if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
+ mask |= EPOLLIN;
+
+ if (test_bit(CACHEFILES_CULLING, &cache->flags))
+ mask |= EPOLLOUT;
+
+ return mask;
+}
+
+/*
+ * Give a range error for cache space constraints
+ * - can be tail-called
+ */
+static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
+ char *args)
+{
+ pr_err("Free space limits must be in range 0%%<=stop<cull<run<100%%\n");
+
+ return -EINVAL;
+}
+
+/*
+ * Set the percentage of files at which to stop culling
+ * - command: "frun <N>%"
+ */
+static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
+{
+ unsigned long frun;
+
+ _enter(",%s", args);
+
+ if (!*args)
+ return -EINVAL;
+
+ frun = simple_strtoul(args, &args, 10);
+ if (args[0] != '%' || args[1] != '\0')
+ return -EINVAL;
+
+ if (frun <= cache->fcull_percent || frun >= 100)
+ return cachefiles_daemon_range_error(cache, args);
+
+ cache->frun_percent = frun;
+ return 0;
+}
+
+/*
+ * Set the percentage of files at which to start culling
+ * - command: "fcull <N>%"
+ */
+static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
+{
+ unsigned long fcull;
+
+ _enter(",%s", args);
+
+ if (!*args)
+ return -EINVAL;
+
+ fcull = simple_strtoul(args, &args, 10);
+ if (args[0] != '%' || args[1] != '\0')
+ return -EINVAL;
+
+ if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
+ return cachefiles_daemon_range_error(cache, args);
+
+ cache->fcull_percent = fcull;
+ return 0;
+}
+
+/*
+ * Set the percentage of files at which to stop allocating
+ * - command: "fstop <N>%"
+ */
+static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
+{
+ unsigned long fstop;
+
+ _enter(",%s", args);
+
+ if (!*args)
+ return -EINVAL;
+
+ fstop = simple_strtoul(args, &args, 10);
+ if (args[0] != '%' || args[1] != '\0')
+ return -EINVAL;
+
+ if (fstop >= cache->fcull_percent)
+ return cachefiles_daemon_range_error(cache, args);
+
+ cache->fstop_percent = fstop;
+ return 0;
+}
+
+/*
+ * Set the percentage of blocks at which to stop culling
+ * - command: "brun <N>%"
+ */
+static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
+{
+ unsigned long brun;
+
+ _enter(",%s", args);
+
+ if (!*args)
+ return -EINVAL;
+
+ brun = simple_strtoul(args, &args, 10);
+ if (args[0] != '%' || args[1] != '\0')
+ return -EINVAL;
+
+ if (brun <= cache->bcull_percent || brun >= 100)
+ return cachefiles_daemon_range_error(cache, args);
+
+ cache->brun_percent = brun;
+ return 0;
+}
+
+/*
+ * Set the percentage of blocks at which to start culling
+ * - command: "bcull <N>%"
+ */
+static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
+{
+ unsigned long bcull;
+
+ _enter(",%s", args);
+
+ if (!*args)
+ return -EINVAL;
+
+ bcull = simple_strtoul(args, &args, 10);
+ if (args[0] != '%' || args[1] != '\0')
+ return -EINVAL;
+
+ if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
+ return cachefiles_daemon_range_error(cache, args);
+
+ cache->bcull_percent = bcull;
+ return 0;
+}
+
+/*
+ * Set the percentage of blocks at which to stop allocating
+ * - command: "bstop <N>%"
+ */
+static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
+{
+ unsigned long bstop;
+
+ _enter(",%s", args);
+
+ if (!*args)
+ return -EINVAL;
+
+ bstop = simple_strtoul(args, &args, 10);
+ if (args[0] != '%' || args[1] != '\0')
+ return -EINVAL;
+
+ if (bstop >= cache->bcull_percent)
+ return cachefiles_daemon_range_error(cache, args);
+
+ cache->bstop_percent = bstop;
+ return 0;
+}
+
+/*
+ * Set the cache directory
+ * - command: "dir <name>"
+ */
+static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
+{
+ char *dir;
+
+ _enter(",%s", args);
+
+ if (!*args) {
+ pr_err("Empty directory specified\n");
+ return -EINVAL;
+ }
+
+ if (cache->rootdirname) {
+ pr_err("Second cache directory specified\n");
+ return -EEXIST;
+ }
+
+ dir = kstrdup(args, GFP_KERNEL);
+ if (!dir)
+ return -ENOMEM;
+
+ cache->rootdirname = dir;
+ return 0;
+}
+
+/*
+ * 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("");
+}
diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index e57ce5ef875c..7fd5429715ea 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -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
*/
diff --git a/fs/cachefiles/main.c b/fs/cachefiles/main.c
index 387d42c7185f..533e3067d80f 100644
--- a/fs/cachefiles/main.c
+++ b/fs/cachefiles/main.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();
}
