// 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"

static atomic_t cachefiles_object_debug_id;

/*
 * Allocate a cache object record.
 */
static
struct cachefiles_object *cachefiles_alloc_object(struct fscache_cookie *cookie)
{
        struct fscache_volume *vcookie = cookie->volume;
        struct cachefiles_volume *volume = vcookie->cache_priv;
        struct cachefiles_object *object;

        _enter("{%s},%x,", vcookie->key, cookie->debug_id);

        object = kmem_cache_zalloc(cachefiles_object_jar, GFP_KERNEL);
        if (!object)
                return NULL;

        refcount_set(&object->ref, 1);

        spin_lock_init(&object->lock);
        INIT_LIST_HEAD(&object->cache_link);
        object->volume = volume;
        object->debug_id = atomic_inc_return(&cachefiles_object_debug_id);
        object->cookie = fscache_get_cookie(cookie, fscache_cookie_get_attach_object);

        fscache_count_object(vcookie->cache);
        trace_cachefiles_ref(object->debug_id, cookie->debug_id, 1,
                             cachefiles_obj_new);
        return object;
}

/*
 * Note that an object has been seen.
 */
void cachefiles_see_object(struct cachefiles_object *object,
                           enum cachefiles_obj_ref_trace why)
{
        trace_cachefiles_ref(object->debug_id, object->cookie->debug_id,
                             refcount_read(&object->ref), why);
}

/*
 * Increment the usage count on an object;
 */
struct cachefiles_object *cachefiles_grab_object(struct cachefiles_object *object,
                                                 enum cachefiles_obj_ref_trace why)
{
        int r;

        __refcount_inc(&object->ref, &r);
        trace_cachefiles_ref(object->debug_id, object->cookie->debug_id, r, why);
        return object;
}

/*
 * dispose of a reference to an object
 */
void cachefiles_put_object(struct cachefiles_object *object,
                           enum cachefiles_obj_ref_trace why)
{
        unsigned int object_debug_id = object->debug_id;
        unsigned int cookie_debug_id = object->cookie->debug_id;
        struct fscache_cache *cache;
        bool done;
        int r;

        done = __refcount_dec_and_test(&object->ref, &r);
        trace_cachefiles_ref(object_debug_id, cookie_debug_id, r, why);
        if (done) {
                _debug("- kill object OBJ%x", object_debug_id);

                ASSERTCMP(object->file, ==, NULL);

                kfree(object->d_name);

                cache = object->volume->cache->cache;
                fscache_put_cookie(object->cookie, fscache_cookie_put_object);
                object->cookie = NULL;
                kmem_cache_free(cachefiles_object_jar, object);
                fscache_uncount_object(cache);
        }

        _leave("");
}

/*
 * Adjust the size of a cache file if necessary to match the DIO size.  We keep
 * the EOF marker a multiple of DIO blocks so that we don't fall back to doing
 * non-DIO for a partial block straddling the EOF, but we also have to be
 * careful of someone expanding the file and accidentally accreting the
 * padding.
 */
static int cachefiles_adjust_size(struct cachefiles_object *object)
{
        struct iattr newattrs;
        struct file *file = object->file;
        uint64_t ni_size;
        loff_t oi_size;
        int ret;

        ni_size = object->cookie->object_size;
        ni_size = round_up(ni_size, CACHEFILES_DIO_BLOCK_SIZE);

        _enter("{OBJ%x},[%llu]",
               object->debug_id, (unsigned long long) ni_size);

        if (!file)
                return -ENOBUFS;

        oi_size = i_size_read(file_inode(file));
        if (oi_size == ni_size)
                return 0;

        inode_lock(file_inode(file));

        /* if there's an extension to a partial page at the end of the backing
         * file, we need to discard the partial page so that we pick up new
         * data after it */
        if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
                _debug("discard tail %llx", oi_size);
                newattrs.ia_valid = ATTR_SIZE;
                newattrs.ia_size = oi_size & PAGE_MASK;
                ret = cachefiles_inject_remove_error();
                if (ret == 0)
                        ret = notify_change(&init_user_ns, file->f_path.dentry,
                                            &newattrs, NULL);
                if (ret < 0)
                        goto truncate_failed;
        }

        newattrs.ia_valid = ATTR_SIZE;
        newattrs.ia_size = ni_size;
        ret = cachefiles_inject_write_error();
        if (ret == 0)
                ret = notify_change(&init_user_ns, file->f_path.dentry,
                                    &newattrs, NULL);

truncate_failed:
        inode_unlock(file_inode(file));

        if (ret < 0)
                trace_cachefiles_io_error(NULL, file_inode(file), ret,
                                          cachefiles_trace_notify_change_error);
        if (ret == -EIO) {
                cachefiles_io_error_obj(object, "Size set failed");
                ret = -ENOBUFS;
        }

        _leave(" = %d", ret);
        return ret;
}

/*
 * Attempt to look up the nominated node in this cache
 */
static bool cachefiles_lookup_cookie(struct fscache_cookie *cookie)
{
        struct cachefiles_object *object;
        struct cachefiles_cache *cache = cookie->volume->cache->cache_priv;
        const struct cred *saved_cred;
        bool success;

        object = cachefiles_alloc_object(cookie);
        if (!object)
                goto fail;

        _enter("{OBJ%x}", object->debug_id);

        if (!cachefiles_cook_key(object))
                goto fail_put;

        cookie->cache_priv = object;

        cachefiles_begin_secure(cache, &saved_cred);

        success = cachefiles_look_up_object(object);
        if (!success)
                goto fail_withdraw;

        cachefiles_see_object(object, cachefiles_obj_see_lookup_cookie);

        spin_lock(&cache->object_list_lock);
        list_add(&object->cache_link, &cache->object_list);
        spin_unlock(&cache->object_list_lock);
        cachefiles_adjust_size(object);

        cachefiles_end_secure(cache, saved_cred);
        _leave(" = t");
        return true;

fail_withdraw:
        cachefiles_end_secure(cache, saved_cred);
        cachefiles_see_object(object, cachefiles_obj_see_lookup_failed);
        fscache_caching_failed(cookie);
        _debug("failed c=%08x o=%08x", cookie->debug_id, object->debug_id);
        /* The caller holds an access count on the cookie, so we need them to
         * drop it before we can withdraw the object.
         */
        return false;

fail_put:
        cachefiles_put_object(object, cachefiles_obj_put_alloc_fail);
fail:
        return false;
}

/*
 * Shorten the backing object to discard any dirty data and free up
 * any unused granules.
 */
static bool cachefiles_shorten_object(struct cachefiles_object *object,
                                      struct file *file, loff_t new_size)
{
        struct cachefiles_cache *cache = object->volume->cache;
        struct inode *inode = file_inode(file);
        loff_t i_size, dio_size;
        int ret;

        dio_size = round_up(new_size, CACHEFILES_DIO_BLOCK_SIZE);
        i_size = i_size_read(inode);

        trace_cachefiles_trunc(object, inode, i_size, dio_size,
                               cachefiles_trunc_shrink);
        ret = cachefiles_inject_remove_error();
        if (ret == 0)
                ret = vfs_truncate(&file->f_path, dio_size);
        if (ret < 0) {
                trace_cachefiles_io_error(object, file_inode(file), ret,
                                          cachefiles_trace_trunc_error);
                cachefiles_io_error_obj(object, "Trunc-to-size failed %d", ret);
                cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
                return false;
        }

        if (new_size < dio_size) {
                trace_cachefiles_trunc(object, inode, dio_size, new_size,
                                       cachefiles_trunc_dio_adjust);
                ret = cachefiles_inject_write_error();
                if (ret == 0)
                        ret = vfs_fallocate(file, FALLOC_FL_ZERO_RANGE,
                                            new_size, dio_size - new_size);
                if (ret < 0) {
                        trace_cachefiles_io_error(object, file_inode(file), ret,
                                                  cachefiles_trace_fallocate_error);
                        cachefiles_io_error_obj(object, "Trunc-to-dio-size failed %d", ret);
                        cachefiles_remove_object_xattr(cache, object, file->f_path.dentry);
                        return false;
                }
        }

        return true;
}

/*
 * Resize the backing object.
 */
static void cachefiles_resize_cookie(struct netfs_cache_resources *cres,
                                     loff_t new_size)
{
        struct cachefiles_object *object = cachefiles_cres_object(cres);
        struct cachefiles_cache *cache = object->volume->cache;
        struct fscache_cookie *cookie = object->cookie;
        const struct cred *saved_cred;
        struct file *file = cachefiles_cres_file(cres);
        loff_t old_size = cookie->object_size;

        _enter("%llu->%llu", old_size, new_size);

        if (new_size < old_size) {
                cachefiles_begin_secure(cache, &saved_cred);
                cachefiles_shorten_object(object, file, new_size);
                cachefiles_end_secure(cache, saved_cred);
                object->cookie->object_size = new_size;
                return;
        }

        /* The file is being expanded.  We don't need to do anything
         * particularly.  cookie->initial_size doesn't change and so the point
         * at which we have to download before doesn't change.
         */
        cookie->object_size = new_size;
}

/*
 * Commit changes to the object as we drop it.
 */
static void cachefiles_commit_object(struct cachefiles_object *object,
                                     struct cachefiles_cache *cache)
{
        bool update = false;

        if (test_and_clear_bit(FSCACHE_COOKIE_LOCAL_WRITE, &object->cookie->flags))
                update = true;
        if (test_and_clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags))
                update = true;
        if (update)
                cachefiles_set_object_xattr(object);

        if (test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags))
                cachefiles_commit_tmpfile(cache, object);
}

/*
 * Finalise and object and close the VFS structs that we have.
 */
static void cachefiles_clean_up_object(struct cachefiles_object *object,
                                       struct cachefiles_cache *cache)
{
        if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) {
                if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
                        cachefiles_see_object(object, cachefiles_obj_see_clean_delete);
                        _debug("- inval object OBJ%x", object->debug_id);
                        cachefiles_delete_object(object, FSCACHE_OBJECT_WAS_RETIRED);
                } else {
                        cachefiles_see_object(object, cachefiles_obj_see_clean_drop_tmp);
                        _debug("- inval object OBJ%x tmpfile", object->debug_id);
                }
        } else {
                cachefiles_see_object(object, cachefiles_obj_see_clean_commit);
                cachefiles_commit_object(object, cache);
        }

        cachefiles_unmark_inode_in_use(object, object->file);
        if (object->file) {
                fput(object->file);
                object->file = NULL;
        }
}

/*
 * Withdraw caching for a cookie.
 */
static void cachefiles_withdraw_cookie(struct fscache_cookie *cookie)
{
        struct cachefiles_object *object = cookie->cache_priv;
        struct cachefiles_cache *cache = object->volume->cache;
        const struct cred *saved_cred;

        _enter("o=%x", object->debug_id);
        cachefiles_see_object(object, cachefiles_obj_see_withdraw_cookie);

        if (!list_empty(&object->cache_link)) {
                spin_lock(&cache->object_list_lock);
                cachefiles_see_object(object, cachefiles_obj_see_withdrawal);
                list_del_init(&object->cache_link);
                spin_unlock(&cache->object_list_lock);
        }

        if (object->file) {
                cachefiles_begin_secure(cache, &saved_cred);
                cachefiles_clean_up_object(object, cache);
                cachefiles_end_secure(cache, saved_cred);
        }

        cookie->cache_priv = NULL;
        cachefiles_put_object(object, cachefiles_obj_put_detach);
}

/*
 * Invalidate the storage associated with a cookie.
 */
static bool cachefiles_invalidate_cookie(struct fscache_cookie *cookie)
{
        struct cachefiles_object *object = cookie->cache_priv;
        struct file *new_file, *old_file;
        bool old_tmpfile;

        _enter("o=%x,[%llu]", object->debug_id, object->cookie->object_size);

        old_tmpfile = test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);

        if (!object->file) {
                fscache_resume_after_invalidation(cookie);
                _leave(" = t [light]");
                return true;
        }

        new_file = cachefiles_create_tmpfile(object);
        if (IS_ERR(new_file))
                goto failed;

        /* Substitute the VFS target */
        _debug("sub");
        spin_lock(&object->lock);

        old_file = object->file;
        object->file = new_file;
        object->content_info = CACHEFILES_CONTENT_NO_DATA;
        set_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags);
        set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &object->cookie->flags);

        spin_unlock(&object->lock);
        _debug("subbed");

        /* Allow I/O to take place again */
        fscache_resume_after_invalidation(cookie);

        if (old_file) {
                if (!old_tmpfile) {
                        struct cachefiles_volume *volume = object->volume;
                        struct dentry *fan = volume->fanout[(u8)cookie->key_hash];

                        inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
                        cachefiles_bury_object(volume->cache, object, fan,
                                               old_file->f_path.dentry,
                                               FSCACHE_OBJECT_INVALIDATED);
                }
                fput(old_file);
        }

        _leave(" = t");
        return true;

failed:
        _leave(" = f");
        return false;
}

const struct fscache_cache_ops cachefiles_cache_ops = {
        .name                   = "cachefiles",
        .acquire_volume         = cachefiles_acquire_volume,
        .free_volume            = cachefiles_free_volume,
        .lookup_cookie          = cachefiles_lookup_cookie,
        .withdraw_cookie        = cachefiles_withdraw_cookie,
        .invalidate_cookie      = cachefiles_invalidate_cookie,
        .begin_operation        = cachefiles_begin_operation,
        .resize_cookie          = cachefiles_resize_cookie,
        .prepare_to_write       = cachefiles_prepare_to_write,
};