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    Subject[PATCH 40/64] cachefiles: Implement cache registration and withdrawal
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    Date
    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: David Howells <dhowells@redhat.com>
    cc: linux-cachefs@redhat.com
    ---

    fs/cachefiles/Makefile | 1
    fs/cachefiles/cache.c | 207 +++++++++++++++++++++++++++++++++++++++++++++
    fs/cachefiles/daemon.c | 8 +-
    fs/cachefiles/interface.c | 18 ++++
    fs/cachefiles/internal.h | 9 ++
    5 files changed, 240 insertions(+), 3 deletions(-)
    create mode 100644 fs/cachefiles/interface.c

    diff --git a/fs/cachefiles/Makefile b/fs/cachefiles/Makefile
    index e0b092ca077f..92af5daee8ce 100644
    --- a/fs/cachefiles/Makefile
    +++ b/fs/cachefiles/Makefile
    @@ -6,6 +6,7 @@
    cachefiles-y := \
    cache.o \
    daemon.o \
    + interface.o \
    main.o \
    namei.o \
    security.o
    diff --git a/fs/cachefiles/cache.c b/fs/cachefiles/cache.c
    index 73636f89eefa..4c4121105750 100644
    --- a/fs/cachefiles/cache.c
    +++ b/fs/cachefiles/cache.c
    @@ -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");
    + 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");
    + 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);
    +}
    diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
    index 7d4691614cec..a449ee661987 100644
    --- a/fs/cachefiles/daemon.c
    +++ b/fs/cachefiles/daemon.c
    @@ -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);
    diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
    new file mode 100644
    index 000000000000..564ea8fa6641
    --- /dev/null
    +++ b/fs/cachefiles/interface.c
    @@ -0,0 +1,18 @@
    +// 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",
    +};
    diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
    index 65e01ac1da39..0ccea2373b40 100644
    --- a/fs/cachefiles/internal.h
    +++ b/fs/cachefiles/internal.h
    @@ -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
    */

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