cachefiles: Implement culling daemon commands
Implement the ability for the userspace daemon to try and cull a file or
directory in the cache. Two daemon commands are implemented:
(1) The "inuse" command. This queries if a file is in use or whether it
can be deleted. It checks the S_KERNEL_FILE flag on the inode
referred to by the specified filename.
(2) The "cull" command. This asks for a file or directory to be removed,
where removal means either unlinking it or moving it to the graveyard
directory for userspace to dismantle.
Changes
=======
ver #2:
- Fix logging of wrong error[1].
- Need to unmark an inode we've moved to the graveyard before unlocking.
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/20211203094950.GA2480@kili/ [1]
Link: https://lore.kernel.org/r/163819643179.215744.13641580295708315695.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906945705.143852.8177595531814485350.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967155792.1823006.1088936326902550910.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021555037.640689.9472627499842585255.stgit@warthog.procyon.org.uk/ # v4
This commit is contained in:
David Howells
parent
169379eaef
commit
07a90e9740
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@ -574,7 +574,7 @@ static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
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goto notdir;
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cachefiles_begin_secure(cache, &saved_cred);
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ret = -ENOANO; // PLACEHOLDER: Do culling
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ret = cachefiles_cull(cache, path.dentry, args);
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cachefiles_end_secure(cache, saved_cred);
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path_put(&path);
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@ -645,7 +645,7 @@ static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
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goto notdir;
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cachefiles_begin_secure(cache, &saved_cred);
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ret = -ENOANO; // PLACEHOLDER: Check if in use
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ret = cachefiles_check_in_use(cache, path.dentry, args);
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cachefiles_end_secure(cache, saved_cred);
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path_put(&path);
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@ -189,12 +189,23 @@ extern struct kmem_cache *cachefiles_object_jar;
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*/
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extern void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
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struct file *file);
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extern int cachefiles_bury_object(struct cachefiles_cache *cache,
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struct cachefiles_object *object,
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struct dentry *dir,
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struct dentry *rep,
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enum fscache_why_object_killed why);
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extern struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
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struct dentry *dir,
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const char *name,
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bool *_is_new);
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extern void cachefiles_put_directory(struct dentry *dir);
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extern int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
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char *filename);
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extern int cachefiles_check_in_use(struct cachefiles_cache *cache,
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struct dentry *dir, char *filename);
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/*
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* security.c
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*/
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@ -217,3 +217,310 @@ void cachefiles_put_directory(struct dentry *dir)
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dput(dir);
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}
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}
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/*
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* Remove a regular file from the cache.
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*/
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static int cachefiles_unlink(struct cachefiles_cache *cache,
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struct cachefiles_object *object,
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struct dentry *dir, struct dentry *dentry,
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enum fscache_why_object_killed why)
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{
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struct path path = {
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.mnt = cache->mnt,
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.dentry = dir,
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};
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int ret;
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trace_cachefiles_unlink(object, dentry, why);
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ret = security_path_unlink(&path, dentry);
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if (ret < 0) {
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cachefiles_io_error(cache, "Unlink security error");
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return ret;
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}
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ret = cachefiles_inject_remove_error();
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if (ret == 0) {
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ret = vfs_unlink(&init_user_ns, d_backing_inode(dir), dentry, NULL);
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if (ret == -EIO)
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cachefiles_io_error(cache, "Unlink failed");
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}
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if (ret != 0)
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trace_cachefiles_vfs_error(object, d_backing_inode(dir), ret,
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cachefiles_trace_unlink_error);
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return ret;
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}
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/*
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* Delete an object representation from the cache
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* - File backed objects are unlinked
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* - Directory backed objects are stuffed into the graveyard for userspace to
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* delete
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*/
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int cachefiles_bury_object(struct cachefiles_cache *cache,
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struct cachefiles_object *object,
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struct dentry *dir,
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struct dentry *rep,
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enum fscache_why_object_killed why)
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{
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struct dentry *grave, *trap;
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struct path path, path_to_graveyard;
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char nbuffer[8 + 8 + 1];
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int ret;
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_enter(",'%pd','%pd'", dir, rep);
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if (rep->d_parent != dir) {
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inode_unlock(d_inode(dir));
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_leave(" = -ESTALE");
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return -ESTALE;
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}
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/* non-directories can just be unlinked */
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if (!d_is_dir(rep)) {
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dget(rep); /* Stop the dentry being negated if it's only pinned
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* by a file struct.
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*/
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ret = cachefiles_unlink(cache, object, dir, rep, why);
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dput(rep);
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inode_unlock(d_inode(dir));
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_leave(" = %d", ret);
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return ret;
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}
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/* directories have to be moved to the graveyard */
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_debug("move stale object to graveyard");
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inode_unlock(d_inode(dir));
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try_again:
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/* first step is to make up a grave dentry in the graveyard */
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sprintf(nbuffer, "%08x%08x",
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(uint32_t) ktime_get_real_seconds(),
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(uint32_t) atomic_inc_return(&cache->gravecounter));
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/* do the multiway lock magic */
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trap = lock_rename(cache->graveyard, dir);
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/* do some checks before getting the grave dentry */
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if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {
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/* the entry was probably culled when we dropped the parent dir
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* lock */
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unlock_rename(cache->graveyard, dir);
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_leave(" = 0 [culled?]");
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return 0;
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}
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if (!d_can_lookup(cache->graveyard)) {
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unlock_rename(cache->graveyard, dir);
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cachefiles_io_error(cache, "Graveyard no longer a directory");
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return -EIO;
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}
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if (trap == rep) {
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unlock_rename(cache->graveyard, dir);
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cachefiles_io_error(cache, "May not make directory loop");
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return -EIO;
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}
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if (d_mountpoint(rep)) {
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unlock_rename(cache->graveyard, dir);
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cachefiles_io_error(cache, "Mountpoint in cache");
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return -EIO;
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}
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grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer));
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if (IS_ERR(grave)) {
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unlock_rename(cache->graveyard, dir);
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trace_cachefiles_vfs_error(object, d_inode(cache->graveyard),
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PTR_ERR(grave),
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cachefiles_trace_lookup_error);
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if (PTR_ERR(grave) == -ENOMEM) {
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_leave(" = -ENOMEM");
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return -ENOMEM;
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}
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cachefiles_io_error(cache, "Lookup error %ld", PTR_ERR(grave));
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return -EIO;
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}
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if (d_is_positive(grave)) {
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unlock_rename(cache->graveyard, dir);
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dput(grave);
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grave = NULL;
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cond_resched();
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goto try_again;
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}
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if (d_mountpoint(grave)) {
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unlock_rename(cache->graveyard, dir);
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dput(grave);
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cachefiles_io_error(cache, "Mountpoint in graveyard");
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return -EIO;
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}
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/* target should not be an ancestor of source */
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if (trap == grave) {
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unlock_rename(cache->graveyard, dir);
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dput(grave);
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cachefiles_io_error(cache, "May not make directory loop");
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return -EIO;
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}
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/* attempt the rename */
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path.mnt = cache->mnt;
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path.dentry = dir;
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path_to_graveyard.mnt = cache->mnt;
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path_to_graveyard.dentry = cache->graveyard;
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ret = security_path_rename(&path, rep, &path_to_graveyard, grave, 0);
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if (ret < 0) {
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cachefiles_io_error(cache, "Rename security error %d", ret);
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} else {
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struct renamedata rd = {
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.old_mnt_userns = &init_user_ns,
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.old_dir = d_inode(dir),
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.old_dentry = rep,
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.new_mnt_userns = &init_user_ns,
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.new_dir = d_inode(cache->graveyard),
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.new_dentry = grave,
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};
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trace_cachefiles_rename(object, rep, grave, why);
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ret = cachefiles_inject_read_error();
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if (ret == 0)
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ret = vfs_rename(&rd);
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if (ret != 0)
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trace_cachefiles_vfs_error(object, d_inode(dir), ret,
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cachefiles_trace_rename_error);
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if (ret != 0 && ret != -ENOMEM)
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cachefiles_io_error(cache,
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"Rename failed with error %d", ret);
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}
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__cachefiles_unmark_inode_in_use(object, rep);
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unlock_rename(cache->graveyard, dir);
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dput(grave);
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_leave(" = 0");
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return 0;
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}
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/*
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* Look up an inode to be checked or culled. Return -EBUSY if the inode is
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* marked in use.
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*/
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static struct dentry *cachefiles_lookup_for_cull(struct cachefiles_cache *cache,
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struct dentry *dir,
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char *filename)
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{
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struct dentry *victim;
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int ret = -ENOENT;
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inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
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victim = lookup_one_len(filename, dir, strlen(filename));
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if (IS_ERR(victim))
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goto lookup_error;
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if (d_is_negative(victim))
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goto lookup_put;
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if (d_inode(victim)->i_flags & S_KERNEL_FILE)
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goto lookup_busy;
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return victim;
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lookup_busy:
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ret = -EBUSY;
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lookup_put:
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inode_unlock(d_inode(dir));
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dput(victim);
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return ERR_PTR(ret);
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lookup_error:
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inode_unlock(d_inode(dir));
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ret = PTR_ERR(victim);
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if (ret == -ENOENT)
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return ERR_PTR(-ESTALE); /* Probably got retired by the netfs */
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if (ret == -EIO) {
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cachefiles_io_error(cache, "Lookup failed");
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} else if (ret != -ENOMEM) {
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pr_err("Internal error: %d\n", ret);
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ret = -EIO;
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}
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return ERR_PTR(ret);
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}
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/*
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* Cull an object if it's not in use
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* - called only by cache manager daemon
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*/
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int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
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char *filename)
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{
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struct dentry *victim;
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struct inode *inode;
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int ret;
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_enter(",%pd/,%s", dir, filename);
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victim = cachefiles_lookup_for_cull(cache, dir, filename);
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if (IS_ERR(victim))
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return PTR_ERR(victim);
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/* check to see if someone is using this object */
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inode = d_inode(victim);
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inode_lock(inode);
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if (inode->i_flags & S_KERNEL_FILE) {
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ret = -EBUSY;
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} else {
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/* Stop the cache from picking it back up */
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inode->i_flags |= S_KERNEL_FILE;
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ret = 0;
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}
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inode_unlock(inode);
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if (ret < 0)
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goto error_unlock;
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ret = cachefiles_bury_object(cache, NULL, dir, victim,
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FSCACHE_OBJECT_WAS_CULLED);
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if (ret < 0)
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goto error;
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dput(victim);
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_leave(" = 0");
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return 0;
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error_unlock:
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inode_unlock(d_inode(dir));
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error:
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dput(victim);
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if (ret == -ENOENT)
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return -ESTALE; /* Probably got retired by the netfs */
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if (ret != -ENOMEM) {
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pr_err("Internal error: %d\n", ret);
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ret = -EIO;
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}
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_leave(" = %d", ret);
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return ret;
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}
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/*
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* Find out if an object is in use or not
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* - called only by cache manager daemon
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* - returns -EBUSY or 0 to indicate whether an object is in use or not
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*/
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int cachefiles_check_in_use(struct cachefiles_cache *cache, struct dentry *dir,
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char *filename)
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{
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struct dentry *victim;
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int ret = 0;
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victim = cachefiles_lookup_for_cull(cache, dir, filename);
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if (IS_ERR(victim))
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return PTR_ERR(victim);
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inode_unlock(d_inode(dir));
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dput(victim);
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return ret;
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}
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