Commit d1065b0a authored by David Howells's avatar David Howells
Browse files

cachefiles: Implement cache registration and withdrawal 



Do the following:

 (1) Fill out cachefiles_daemon_add_cache() so that it sets up the cache
     directories and registers the cache with cachefiles.

 (2) Add a function to do the top-level part of cache withdrawal and
     unregistration.

 (3) Add a function to sync a cache.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819633175.215744.10857127598041268340.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906935445.143852.15545194974036410029.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967142904.1823006.244055483596047072.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021543872.640689.14370017789605073222.stgit@warthog.procyon.org.uk/ # v4
parent 32759f7d

fs/cachefiles/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
cachefiles-y := \

	cache.o \

	daemon.o \

	interface.o \

	main.o \

	namei.o \

	security.o

fs/cachefiles/cache.c

+207 −0
Original line number Diff line number Diff line
@@ -10,6 +10,166 @@ 
#include <linux/namei.h>

#include "internal.h"



/*

 * Bring a cache online.

 */

int cachefiles_add_cache(struct cachefiles_cache *cache)

{

	struct fscache_cache *cache_cookie;

	struct path path;

	struct kstatfs stats;

	struct dentry *graveyard, *cachedir, *root;

	const struct cred *saved_cred;

	int ret;



	_enter("");



	cache_cookie = fscache_acquire_cache(cache->tag);

	if (IS_ERR(cache_cookie))

		return PTR_ERR(cache_cookie);



	/* we want to work under the module's security ID */

	ret = cachefiles_get_security_ID(cache);

	if (ret < 0)

		goto error_getsec;



	cachefiles_begin_secure(cache, &saved_cred);



	/* look up the directory at the root of the cache */

	ret = kern_path(cache->rootdirname, LOOKUP_DIRECTORY, &path);

	if (ret < 0)

		goto error_open_root;



	cache->mnt = path.mnt;

	root = path.dentry;



	ret = -EINVAL;

	if (mnt_user_ns(path.mnt) != &init_user_ns) {

		pr_warn("File cache on idmapped mounts not supported");

		goto error_unsupported;

	}



	/* check parameters */

	ret = -EOPNOTSUPP;

	if (d_is_negative(root) ||

	    !d_backing_inode(root)->i_op->lookup ||

	    !d_backing_inode(root)->i_op->mkdir ||

	    !(d_backing_inode(root)->i_opflags & IOP_XATTR) ||

	    !root->d_sb->s_op->statfs ||

	    !root->d_sb->s_op->sync_fs ||

	    root->d_sb->s_blocksize > PAGE_SIZE)

		goto error_unsupported;



	ret = -EROFS;

	if (sb_rdonly(root->d_sb))

		goto error_unsupported;



	/* determine the security of the on-disk cache as this governs

	 * security ID of files we create */

	ret = cachefiles_determine_cache_security(cache, root, &saved_cred);

	if (ret < 0)

		goto error_unsupported;



	/* get the cache size and blocksize */

	ret = vfs_statfs(&path, &stats);

	if (ret < 0)

		goto error_unsupported;



	ret = -ERANGE;

	if (stats.f_bsize <= 0)

		goto error_unsupported;



	ret = -EOPNOTSUPP;

	if (stats.f_bsize > PAGE_SIZE)

		goto error_unsupported;



	cache->bsize = stats.f_bsize;

	cache->bshift = 0;

	if (stats.f_bsize < PAGE_SIZE)

		cache->bshift = PAGE_SHIFT - ilog2(stats.f_bsize);



	_debug("blksize %u (shift %u)",

	       cache->bsize, cache->bshift);



	_debug("size %llu, avail %llu",

	       (unsigned long long) stats.f_blocks,

	       (unsigned long long) stats.f_bavail);



	/* set up caching limits */

	do_div(stats.f_files, 100);

	cache->fstop = stats.f_files * cache->fstop_percent;

	cache->fcull = stats.f_files * cache->fcull_percent;

	cache->frun  = stats.f_files * cache->frun_percent;



	_debug("limits {%llu,%llu,%llu} files",

	       (unsigned long long) cache->frun,

	       (unsigned long long) cache->fcull,

	       (unsigned long long) cache->fstop);



	stats.f_blocks >>= cache->bshift;

	do_div(stats.f_blocks, 100);

	cache->bstop = stats.f_blocks * cache->bstop_percent;

	cache->bcull = stats.f_blocks * cache->bcull_percent;

	cache->brun  = stats.f_blocks * cache->brun_percent;



	_debug("limits {%llu,%llu,%llu} blocks",

	       (unsigned long long) cache->brun,

	       (unsigned long long) cache->bcull,

	       (unsigned long long) cache->bstop);



	/* get the cache directory and check its type */

	cachedir = cachefiles_get_directory(cache, root, "cache", NULL);

	if (IS_ERR(cachedir)) {

		ret = PTR_ERR(cachedir);

		goto error_unsupported;

	}



	cache->store = cachedir;



	/* get the graveyard directory */

	graveyard = cachefiles_get_directory(cache, root, "graveyard", NULL);

	if (IS_ERR(graveyard)) {

		ret = PTR_ERR(graveyard);

		goto error_unsupported;

	}



	cache->graveyard = graveyard;

	cache->cache = cache_cookie;



	ret = fscache_add_cache(cache_cookie, &cachefiles_cache_ops, cache);

	if (ret < 0)

		goto error_add_cache;



	/* done */

	set_bit(CACHEFILES_READY, &cache->flags);

	dput(root);



	pr_info("File cache on %s registered\n", cache_cookie->name);



	/* check how much space the cache has */

	cachefiles_has_space(cache, 0, 0);

	cachefiles_end_secure(cache, saved_cred);

	_leave(" = 0 [%px]", cache->cache);

	return 0;



error_add_cache:

	cachefiles_put_directory(cache->graveyard);

	cache->graveyard = NULL;

error_unsupported:

	cachefiles_put_directory(cache->store);

	cache->store = NULL;

	mntput(cache->mnt);

	cache->mnt = NULL;

	dput(root);

error_open_root:

	cachefiles_end_secure(cache, saved_cred);

error_getsec:

	fscache_relinquish_cache(cache_cookie);

	cache->cache = NULL;

	pr_err("Failed to register: %d\n", ret);

	return ret;

}



/*

 * See if we have space for a number of pages and/or a number of files in the

 * cache
@@ -101,3 +261,50 @@ int cachefiles_has_space(struct cachefiles_cache *cache, 
	_leave(" = %d", ret);

	return ret;

}



/*

 * Sync a cache to backing disk.

 */

static void cachefiles_sync_cache(struct cachefiles_cache *cache)

{

	const struct cred *saved_cred;

	int ret;



	_enter("%s", cache->cache->name);



	/* make sure all pages pinned by operations on behalf of the netfs are

	 * written to disc */

	cachefiles_begin_secure(cache, &saved_cred);

	down_read(&cache->mnt->mnt_sb->s_umount);

	ret = sync_filesystem(cache->mnt->mnt_sb);

	up_read(&cache->mnt->mnt_sb->s_umount);

	cachefiles_end_secure(cache, saved_cred);



	if (ret == -EIO)

		cachefiles_io_error(cache,

				    "Attempt to sync backing fs superblock returned error %d",

				    ret);

}



/*

 * Withdraw cache objects.

 */

void cachefiles_withdraw_cache(struct cachefiles_cache *cache)

{

	struct fscache_cache *fscache = cache->cache;



	pr_info("File cache on %s unregistering\n", fscache->name);



	fscache_withdraw_cache(fscache);



	/* we now have to destroy all the active objects pertaining to this

	 * cache - which we do by passing them off to thread pool to be

	 * disposed of */

	// PLACEHOLDER: Withdraw objects

	fscache_wait_for_objects(fscache);



	// PLACEHOLDER: Withdraw volume

	cachefiles_sync_cache(cache);

	cache->cache = NULL;

	fscache_relinquish_cache(fscache);

}

fs/cachefiles/daemon.c

+5 −3
Original line number Diff line number Diff line
@@ -702,6 +702,7 @@ static int cachefiles_daemon_bind(struct cachefiles_cache *cache, char *args) 


	pr_warn("Cache is disabled for development\n");

	return -ENOANO; // Don't allow the cache to operate yet

	//return cachefiles_add_cache(cache);

}



/*
@@ -711,10 +712,11 @@ static void cachefiles_daemon_unbind(struct cachefiles_cache *cache) 
{

	_enter("");



	if (test_bit(CACHEFILES_READY, &cache->flags)) {

		// PLACEHOLDER: Withdraw cache

	}

	if (test_bit(CACHEFILES_READY, &cache->flags))

		cachefiles_withdraw_cache(cache);



	cachefiles_put_directory(cache->graveyard);

	cachefiles_put_directory(cache->store);

	mntput(cache->mnt);



	kfree(cache->rootdirname);

fs/cachefiles/interface.c

0 → 100644
+18 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-or-later

/* FS-Cache interface to CacheFiles

 *

 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.

 * Written by David Howells (dhowells@redhat.com)

 */



#include <linux/slab.h>

#include <linux/mount.h>

#include <linux/xattr.h>

#include <linux/file.h>

#include <linux/falloc.h>

#include <trace/events/fscache.h>

#include "internal.h"



const struct fscache_cache_ops cachefiles_cache_ops = {

	.name			= "cachefiles",

};

fs/cachefiles/internal.h

+9 −0
Original line number Diff line number Diff line
@@ -32,6 +32,8 @@ struct cachefiles_object { 
struct cachefiles_cache {

	struct fscache_cache		*cache;		/* Cache cookie */

	struct vfsmount			*mnt;		/* mountpoint holding the cache */

	struct dentry			*store;		/* Directory into which live objects go */

	struct dentry			*graveyard;	/* directory into which dead objects go */

	struct file			*cachefilesd;	/* manager daemon handle */

	const struct cred		*cache_cred;	/* security override for accessing cache */

	struct mutex			daemon_mutex;	/* command serialisation mutex */
@@ -78,8 +80,10 @@ static inline void cachefiles_state_changed(struct cachefiles_cache *cache) 
/*

 * cache.c

 */

extern int cachefiles_add_cache(struct cachefiles_cache *cache);

extern int cachefiles_has_space(struct cachefiles_cache *cache,

				unsigned fnr, unsigned bnr);

extern void cachefiles_withdraw_cache(struct cachefiles_cache *cache);



/*

 * daemon.c
@@ -125,6 +129,11 @@ static inline int cachefiles_inject_remove_error(void) 
	return cachefiles_error_injection_state & 2 ? -EIO : 0;

}



/*

 * interface.c

 */

extern const struct fscache_cache_ops cachefiles_cache_ops;



/*

 * namei.c

 */