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1f08c925e7
Implement the wrangling of backing files, including the following pieces: (1) Lookup and creation of a file on disk, using a tmpfile if the file isn't yet present. The file is then opened, sized for DIO and the file handle is attached to the cachefiles_object struct. The inode is marked to indicate that it's in use by a kernel service. (2) Invalidation of an object, creating a tmpfile and switching the file pointer in the cachefiles object. (3) Committing a file to disk, including setting the coherency xattr on it and, if necessary, creating a hard link to it. Note that this would be a good place to use Omar Sandoval's vfs_link() with AT_LINK_REPLACE[1] as I may have to unlink an old file before I can link a tmpfile into place. (4) Withdrawal of open objects when a cache is being withdrawn or a cookie is relinquished. This involves committing or discarding the file. Changes ======= ver #2: - Fix logging of wrong error[1]. 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/163819644097.215744.4505389616742411239.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906949512.143852.14222856795032602080.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967158526.1823006.17482695321424642675.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021557060.640689.16373541458119269871.stgit@warthog.procyon.org.uk/ # v4
367 lines
9.7 KiB
C
367 lines
9.7 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* FS-Cache interface to CacheFiles
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*
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* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#include <linux/slab.h>
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#include <linux/mount.h>
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#include <linux/xattr.h>
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#include <linux/file.h>
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#include <linux/falloc.h>
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#include <trace/events/fscache.h>
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#include "internal.h"
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static atomic_t cachefiles_object_debug_id;
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/*
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* Allocate a cache object record.
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*/
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static
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struct cachefiles_object *cachefiles_alloc_object(struct fscache_cookie *cookie)
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{
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struct fscache_volume *vcookie = cookie->volume;
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struct cachefiles_volume *volume = vcookie->cache_priv;
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struct cachefiles_object *object;
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_enter("{%s},%x,", vcookie->key, cookie->debug_id);
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object = kmem_cache_zalloc(cachefiles_object_jar, GFP_KERNEL);
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if (!object)
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return NULL;
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refcount_set(&object->ref, 1);
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spin_lock_init(&object->lock);
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INIT_LIST_HEAD(&object->cache_link);
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object->volume = volume;
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object->debug_id = atomic_inc_return(&cachefiles_object_debug_id);
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object->cookie = fscache_get_cookie(cookie, fscache_cookie_get_attach_object);
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fscache_count_object(vcookie->cache);
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trace_cachefiles_ref(object->debug_id, cookie->debug_id, 1,
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cachefiles_obj_new);
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return object;
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}
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/*
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* Note that an object has been seen.
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*/
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void cachefiles_see_object(struct cachefiles_object *object,
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enum cachefiles_obj_ref_trace why)
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{
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trace_cachefiles_ref(object->debug_id, object->cookie->debug_id,
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refcount_read(&object->ref), why);
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}
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/*
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* Increment the usage count on an object;
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*/
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struct cachefiles_object *cachefiles_grab_object(struct cachefiles_object *object,
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enum cachefiles_obj_ref_trace why)
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{
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int r;
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__refcount_inc(&object->ref, &r);
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trace_cachefiles_ref(object->debug_id, object->cookie->debug_id, r, why);
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return object;
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}
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/*
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* dispose of a reference to an object
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*/
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void cachefiles_put_object(struct cachefiles_object *object,
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enum cachefiles_obj_ref_trace why)
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{
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unsigned int object_debug_id = object->debug_id;
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unsigned int cookie_debug_id = object->cookie->debug_id;
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struct fscache_cache *cache;
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bool done;
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int r;
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done = __refcount_dec_and_test(&object->ref, &r);
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trace_cachefiles_ref(object_debug_id, cookie_debug_id, r, why);
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if (done) {
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_debug("- kill object OBJ%x", object_debug_id);
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ASSERTCMP(object->file, ==, NULL);
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kfree(object->d_name);
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cache = object->volume->cache->cache;
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fscache_put_cookie(object->cookie, fscache_cookie_put_object);
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object->cookie = NULL;
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kmem_cache_free(cachefiles_object_jar, object);
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fscache_uncount_object(cache);
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}
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_leave("");
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}
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/*
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* Adjust the size of a cache file if necessary to match the DIO size. We keep
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* the EOF marker a multiple of DIO blocks so that we don't fall back to doing
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* non-DIO for a partial block straddling the EOF, but we also have to be
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* careful of someone expanding the file and accidentally accreting the
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* padding.
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*/
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static int cachefiles_adjust_size(struct cachefiles_object *object)
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{
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struct iattr newattrs;
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struct file *file = object->file;
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uint64_t ni_size;
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loff_t oi_size;
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int ret;
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ni_size = object->cookie->object_size;
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ni_size = round_up(ni_size, CACHEFILES_DIO_BLOCK_SIZE);
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_enter("{OBJ%x},[%llu]",
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object->debug_id, (unsigned long long) ni_size);
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if (!file)
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return -ENOBUFS;
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oi_size = i_size_read(file_inode(file));
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if (oi_size == ni_size)
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return 0;
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inode_lock(file_inode(file));
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/* if there's an extension to a partial page at the end of the backing
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* file, we need to discard the partial page so that we pick up new
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* data after it */
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if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
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_debug("discard tail %llx", oi_size);
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newattrs.ia_valid = ATTR_SIZE;
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newattrs.ia_size = oi_size & PAGE_MASK;
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ret = cachefiles_inject_remove_error();
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if (ret == 0)
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ret = notify_change(&init_user_ns, file->f_path.dentry,
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&newattrs, NULL);
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if (ret < 0)
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goto truncate_failed;
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}
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newattrs.ia_valid = ATTR_SIZE;
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newattrs.ia_size = ni_size;
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ret = cachefiles_inject_write_error();
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if (ret == 0)
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ret = notify_change(&init_user_ns, file->f_path.dentry,
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&newattrs, NULL);
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truncate_failed:
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inode_unlock(file_inode(file));
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if (ret < 0)
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trace_cachefiles_io_error(NULL, file_inode(file), ret,
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cachefiles_trace_notify_change_error);
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if (ret == -EIO) {
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cachefiles_io_error_obj(object, "Size set failed");
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ret = -ENOBUFS;
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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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* Attempt to look up the nominated node in this cache
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*/
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static bool cachefiles_lookup_cookie(struct fscache_cookie *cookie)
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{
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struct cachefiles_object *object;
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struct cachefiles_cache *cache = cookie->volume->cache->cache_priv;
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const struct cred *saved_cred;
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bool success;
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object = cachefiles_alloc_object(cookie);
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if (!object)
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goto fail;
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_enter("{OBJ%x}", object->debug_id);
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if (!cachefiles_cook_key(object))
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goto fail_put;
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cookie->cache_priv = object;
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cachefiles_begin_secure(cache, &saved_cred);
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success = cachefiles_look_up_object(object);
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if (!success)
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goto fail_withdraw;
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cachefiles_see_object(object, cachefiles_obj_see_lookup_cookie);
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spin_lock(&cache->object_list_lock);
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list_add(&object->cache_link, &cache->object_list);
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spin_unlock(&cache->object_list_lock);
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cachefiles_adjust_size(object);
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cachefiles_end_secure(cache, saved_cred);
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_leave(" = t");
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return true;
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fail_withdraw:
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cachefiles_end_secure(cache, saved_cred);
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cachefiles_see_object(object, cachefiles_obj_see_lookup_failed);
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fscache_caching_failed(cookie);
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_debug("failed c=%08x o=%08x", cookie->debug_id, object->debug_id);
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/* The caller holds an access count on the cookie, so we need them to
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* drop it before we can withdraw the object.
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*/
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return false;
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fail_put:
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cachefiles_put_object(object, cachefiles_obj_put_alloc_fail);
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fail:
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return false;
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}
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/*
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* Commit changes to the object as we drop it.
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*/
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static void cachefiles_commit_object(struct cachefiles_object *object,
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struct cachefiles_cache *cache)
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{
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bool update = false;
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if (test_and_clear_bit(FSCACHE_COOKIE_LOCAL_WRITE, &object->cookie->flags))
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update = true;
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if (test_and_clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags))
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update = true;
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if (update)
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cachefiles_set_object_xattr(object);
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if (test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags))
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cachefiles_commit_tmpfile(cache, object);
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}
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/*
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* Finalise and object and close the VFS structs that we have.
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*/
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static void cachefiles_clean_up_object(struct cachefiles_object *object,
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struct cachefiles_cache *cache)
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{
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if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) {
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if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
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cachefiles_see_object(object, cachefiles_obj_see_clean_delete);
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_debug("- inval object OBJ%x", object->debug_id);
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cachefiles_delete_object(object, FSCACHE_OBJECT_WAS_RETIRED);
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} else {
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cachefiles_see_object(object, cachefiles_obj_see_clean_drop_tmp);
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_debug("- inval object OBJ%x tmpfile", object->debug_id);
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}
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} else {
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cachefiles_see_object(object, cachefiles_obj_see_clean_commit);
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cachefiles_commit_object(object, cache);
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}
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cachefiles_unmark_inode_in_use(object, object->file);
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if (object->file) {
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fput(object->file);
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object->file = NULL;
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}
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}
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/*
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* Withdraw caching for a cookie.
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*/
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static void cachefiles_withdraw_cookie(struct fscache_cookie *cookie)
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{
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struct cachefiles_object *object = cookie->cache_priv;
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struct cachefiles_cache *cache = object->volume->cache;
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const struct cred *saved_cred;
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_enter("o=%x", object->debug_id);
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cachefiles_see_object(object, cachefiles_obj_see_withdraw_cookie);
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if (!list_empty(&object->cache_link)) {
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spin_lock(&cache->object_list_lock);
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cachefiles_see_object(object, cachefiles_obj_see_withdrawal);
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list_del_init(&object->cache_link);
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spin_unlock(&cache->object_list_lock);
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}
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if (object->file) {
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cachefiles_begin_secure(cache, &saved_cred);
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cachefiles_clean_up_object(object, cache);
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cachefiles_end_secure(cache, saved_cred);
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}
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cookie->cache_priv = NULL;
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cachefiles_put_object(object, cachefiles_obj_put_detach);
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}
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/*
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* Invalidate the storage associated with a cookie.
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*/
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static bool cachefiles_invalidate_cookie(struct fscache_cookie *cookie)
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{
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struct cachefiles_object *object = cookie->cache_priv;
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struct file *new_file, *old_file;
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bool old_tmpfile;
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_enter("o=%x,[%llu]", object->debug_id, object->cookie->object_size);
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old_tmpfile = test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
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if (!object->file) {
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fscache_resume_after_invalidation(cookie);
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_leave(" = t [light]");
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return true;
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}
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new_file = cachefiles_create_tmpfile(object);
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if (IS_ERR(new_file))
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goto failed;
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/* Substitute the VFS target */
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_debug("sub");
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spin_lock(&object->lock);
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old_file = object->file;
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object->file = new_file;
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object->content_info = CACHEFILES_CONTENT_NO_DATA;
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set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
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set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);
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spin_unlock(&object->lock);
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_debug("subbed");
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/* Allow I/O to take place again */
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fscache_resume_after_invalidation(cookie);
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if (old_file) {
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if (!old_tmpfile) {
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struct cachefiles_volume *volume = object->volume;
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struct dentry *fan = volume->fanout[(u8)cookie->key_hash];
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inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
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cachefiles_bury_object(volume->cache, object, fan,
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old_file->f_path.dentry,
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FSCACHE_OBJECT_INVALIDATED);
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}
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fput(old_file);
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}
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_leave(" = t");
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return true;
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failed:
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_leave(" = f");
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return false;
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}
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const struct fscache_cache_ops cachefiles_cache_ops = {
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.name = "cachefiles",
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.acquire_volume = cachefiles_acquire_volume,
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.free_volume = cachefiles_free_volume,
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.lookup_cookie = cachefiles_lookup_cookie,
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.withdraw_cookie = cachefiles_withdraw_cookie,
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.invalidate_cookie = cachefiles_invalidate_cookie,
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.prepare_to_write = cachefiles_prepare_to_write,
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};
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