On Wed, 2021-12-22 at 23:23 +0000, David Howells wrote:
> 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 <dhowe...@redhat.com>
> cc: linux-cachefs@redhat.com
> Link:
> https://lore.kernel.org/r/163819633175.215744.10857127598041268340.st...@warthog.procyon.org.uk/
> # v1
> Link:
> https://lore.kernel.org/r/163906935445.143852.15545194974036410029.st...@warthog.procyon.org.uk/
> # v2
> Link:
> https://lore.kernel.org/r/163967142904.1823006.244055483596047072.st...@warthog.procyon.org.uk/
> # v3
> ---
>
> 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..0462e7af87fb 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;
> +
That's quite a collection of tests.
Most are obvious, but some comments explaining the need for others would
not be a bad thing. In particular, why is s_blocksize > PAGE_SIZE
unsupported?
Also, should you vet whether the fs supports i_op->tmpfile here ?
> + 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);
> +}
> 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 (dhowe...@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 48768a3ab105..77e874c2bbe7 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
> */
>
>
--
Jeff Layton <jlay...@kernel.org>
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