// SPDX-License-Identifier: GPL-2.0-only

#include "dev.h"
#include "fuse_i.h"
#include <linux/pagemap.h>

static int fuse_notify_poll(struct fuse_conn *fc, unsigned int size,
			    struct fuse_copy_state *cs)
{
	struct fuse_notify_poll_wakeup_out outarg;
	int err;

	if (size != sizeof(outarg))
		return -EINVAL;

	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
	if (err)
		return err;

	fuse_copy_finish(cs);
	return fuse_notify_poll_wakeup(fc, &outarg);
}

static int fuse_notify_inval_inode(struct fuse_conn *fc, unsigned int size,
				   struct fuse_copy_state *cs)
{
	struct fuse_notify_inval_inode_out outarg;
	int err;

	if (size != sizeof(outarg))
		return -EINVAL;

	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
	if (err)
		return err;
	fuse_copy_finish(cs);

	down_read(&fc->killsb);
	err = fuse_reverse_inval_inode(fc, outarg.ino,
				       outarg.off, outarg.len);
	up_read(&fc->killsb);
	return err;
}

static int fuse_notify_inval_entry(struct fuse_conn *fc, unsigned int size,
				   struct fuse_copy_state *cs)
{
	struct fuse_notify_inval_entry_out outarg;
	int err;
	char *buf;
	struct qstr name;

	if (size < sizeof(outarg))
		return -EINVAL;

	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
	if (err)
		return err;

	if (outarg.namelen > fc->name_max)
		return -ENAMETOOLONG;

	err = -EINVAL;
	if (size != sizeof(outarg) + outarg.namelen + 1)
		return -EINVAL;

	buf = kzalloc(outarg.namelen + 1, GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	name.name = buf;
	name.len = outarg.namelen;
	err = fuse_copy_one(cs, buf, outarg.namelen + 1);
	if (err)
		goto err;
	fuse_copy_finish(cs);
	buf[outarg.namelen] = 0;

	down_read(&fc->killsb);
	err = fuse_reverse_inval_entry(fc, outarg.parent, 0, &name, outarg.flags);
	up_read(&fc->killsb);
err:
	kfree(buf);
	return err;
}

static int fuse_notify_delete(struct fuse_conn *fc, unsigned int size,
			      struct fuse_copy_state *cs)
{
	struct fuse_notify_delete_out outarg;
	int err;
	char *buf;
	struct qstr name;

	if (size < sizeof(outarg))
		return -EINVAL;

	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
	if (err)
		return err;

	if (outarg.namelen > fc->name_max)
		return -ENAMETOOLONG;

	if (size != sizeof(outarg) + outarg.namelen + 1)
		return -EINVAL;

	buf = kzalloc(outarg.namelen + 1, GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	name.name = buf;
	name.len = outarg.namelen;
	err = fuse_copy_one(cs, buf, outarg.namelen + 1);
	if (err)
		goto err;
	fuse_copy_finish(cs);
	buf[outarg.namelen] = 0;

	down_read(&fc->killsb);
	err = fuse_reverse_inval_entry(fc, outarg.parent, outarg.child, &name, 0);
	up_read(&fc->killsb);
err:
	kfree(buf);
	return err;
}

static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
			     struct fuse_copy_state *cs)
{
	struct fuse_notify_store_out outarg;
	struct inode *inode;
	struct address_space *mapping;
	u64 nodeid;
	int err;
	unsigned int num;
	loff_t file_size;
	loff_t pos;
	loff_t end;

	if (size < sizeof(outarg))
		return -EINVAL;

	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
	if (err)
		return err;

	if (size - sizeof(outarg) != outarg.size)
		return -EINVAL;

	if (outarg.offset >= MAX_LFS_FILESIZE)
		return -EINVAL;

	nodeid = outarg.nodeid;
	pos = outarg.offset;
	num = min(outarg.size, MAX_LFS_FILESIZE - pos);

	down_read(&fc->killsb);

	err = -ENOENT;
	inode = fuse_ilookup(fc, nodeid,  NULL);
	if (!inode)
		goto out_up_killsb;
	if (!S_ISREG(inode->i_mode)) {
		err = -EINVAL;
		goto out_iput;
	}

	mapping = inode->i_mapping;
	file_size = i_size_read(inode);
	end = pos + num;
	if (end > file_size) {
		file_size = end;
		fuse_write_update_attr(inode, file_size, num);
	}

	while (num) {
		struct folio *folio;
		unsigned int folio_offset;
		unsigned int nr_bytes;
		pgoff_t index = pos >> PAGE_SHIFT;

		folio = filemap_grab_folio(mapping, index);
		err = PTR_ERR(folio);
		if (IS_ERR(folio))
			goto out_iput;

		folio_offset = offset_in_folio(folio, pos);
		nr_bytes = min(num, folio_size(folio) - folio_offset);

		err = fuse_copy_folio(cs, &folio, folio_offset, nr_bytes, 0);
		if (!folio_test_uptodate(folio) && !err && folio_offset == 0 &&
		    (nr_bytes == folio_size(folio) || file_size == end)) {
			folio_zero_segment(folio, nr_bytes, folio_size(folio));
			folio_mark_uptodate(folio);
		}
		folio_unlock(folio);
		folio_put(folio);

		if (err)
			goto out_iput;

		pos += nr_bytes;
		num -= nr_bytes;
	}

	err = 0;

out_iput:
	iput(inode);
out_up_killsb:
	up_read(&fc->killsb);
	return err;
}

struct fuse_retrieve_args {
	struct fuse_args_pages ap;
	struct fuse_notify_retrieve_in inarg;
};

static void fuse_retrieve_end(struct fuse_args *args, int error)
{
	struct fuse_retrieve_args *ra =
		container_of(args, typeof(*ra), ap.args);

	release_pages(ra->ap.folios, ra->ap.num_folios);
	kfree(ra);
}

static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
			 struct fuse_notify_retrieve_out *outarg)
{
	int err;
	struct address_space *mapping = inode->i_mapping;
	loff_t file_size;
	unsigned int num;
	unsigned int offset;
	size_t total_len = 0;
	unsigned int num_pages;
	struct fuse_conn *fc = fm->fc;
	struct fuse_retrieve_args *ra;
	size_t args_size = sizeof(*ra);
	struct fuse_args_pages *ap;
	struct fuse_args *args;
	loff_t pos = outarg->offset;

	offset = offset_in_page(pos);
	file_size = i_size_read(inode);

	num = min(outarg->size, fc->max_write);
	if (pos > file_size)
		num = 0;
	else if (num > file_size - pos)
		num = file_size - pos;

	num_pages = DIV_ROUND_UP(num + offset, PAGE_SIZE);
	num_pages = min(num_pages, fc->max_pages);
	num = min(num, num_pages << PAGE_SHIFT);

	args_size += num_pages * (sizeof(ap->folios[0]) + sizeof(ap->descs[0]));

	ra = kzalloc(args_size, GFP_KERNEL);
	if (!ra)
		return -ENOMEM;

	ap = &ra->ap;
	ap->folios = (void *) (ra + 1);
	ap->descs = (void *) (ap->folios + num_pages);

	args = &ap->args;
	args->nodeid = outarg->nodeid;
	args->opcode = FUSE_NOTIFY_REPLY;
	args->in_numargs = 3;
	args->in_pages = true;
	args->end = fuse_retrieve_end;

	while (num && ap->num_folios < num_pages) {
		struct folio *folio;
		unsigned int folio_offset;
		unsigned int nr_bytes;
		pgoff_t index = pos >> PAGE_SHIFT;

		folio = filemap_get_folio(mapping, index);
		if (IS_ERR(folio))
			break;
		if (!folio_test_uptodate(folio)) {
			folio_put(folio);
			break;
		}

		folio_offset = offset_in_folio(folio, pos);
		nr_bytes = min(folio_size(folio) - folio_offset, num);

		ap->folios[ap->num_folios] = folio;
		ap->descs[ap->num_folios].offset = folio_offset;
		ap->descs[ap->num_folios].length = nr_bytes;
		ap->num_folios++;

		pos += nr_bytes;
		num -= nr_bytes;
		total_len += nr_bytes;
	}
	ra->inarg.offset = outarg->offset;
	ra->inarg.size = total_len;
	fuse_set_zero_arg0(args);
	args->in_args[1].size = sizeof(ra->inarg);
	args->in_args[1].value = &ra->inarg;
	args->in_args[2].size = total_len;

	err = fuse_simple_notify_reply(fm, args, outarg->notify_unique);
	if (err)
		fuse_retrieve_end(args, err);

	return err;
}

static int fuse_notify_retrieve(struct fuse_conn *fc, unsigned int size,
				struct fuse_copy_state *cs)
{
	struct fuse_notify_retrieve_out outarg;
	struct fuse_mount *fm;
	struct inode *inode;
	u64 nodeid;
	int err;

	if (size != sizeof(outarg))
		return -EINVAL;

	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
	if (err)
		return err;

	fuse_copy_finish(cs);

	if (outarg.offset >= MAX_LFS_FILESIZE)
		return -EINVAL;

	down_read(&fc->killsb);
	err = -ENOENT;
	nodeid = outarg.nodeid;

	inode = fuse_ilookup(fc, nodeid, &fm);
	if (inode) {
		err = -EINVAL;
		if (S_ISREG(inode->i_mode))
			err = fuse_retrieve(fm, inode, &outarg);
		iput(inode);
	}
	up_read(&fc->killsb);

	return err;
}

static int fuse_notify_resend(struct fuse_conn *fc)
{
	fuse_chan_resend(fc->chan);
	return 0;
}

/*
 * Increments the fuse connection epoch.  This will cause dentries and
 * readdir caches from previous epochs to be invalidated.  Additionally,
 * if inval_wq is set, a work queue is scheduled to trigger the invalidation.
 */
static int fuse_notify_inc_epoch(struct fuse_conn *fc)
{
	atomic_inc(&fc->epoch);
	if (inval_wq)
		schedule_work(&fc->epoch_work);

	return 0;
}

static int fuse_notify_prune(struct fuse_conn *fc, unsigned int size,
			     struct fuse_copy_state *cs)
{
	struct fuse_notify_prune_out outarg;
	const unsigned int batch = 512;
	u64 *nodeids __free(kfree) = kmalloc(sizeof(u64) * batch, GFP_KERNEL);
	unsigned int num, i;
	int err;

	if (!nodeids)
		return -ENOMEM;

	if (size < sizeof(outarg))
		return -EINVAL;

	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
	if (err)
		return err;

	if (size - sizeof(outarg) != array_size(outarg.count, sizeof(u64)))
		return -EINVAL;

	for (; outarg.count; outarg.count -= num) {
		num = min(batch, outarg.count);
		err = fuse_copy_one(cs, nodeids, num * sizeof(u64));
		if (err)
			return err;

		scoped_guard(rwsem_read, &fc->killsb) {
			for (i = 0; i < num; i++)
				fuse_try_prune_one_inode(fc, nodeids[i]);
		}
	}
	return 0;
}

int fuse_notify(struct fuse_conn *fc, enum fuse_notify_code code,
		unsigned int size, struct fuse_copy_state *cs)
{
	switch (code) {
	case FUSE_NOTIFY_POLL:
		return fuse_notify_poll(fc, size, cs);

	case FUSE_NOTIFY_INVAL_INODE:
		return fuse_notify_inval_inode(fc, size, cs);

	case FUSE_NOTIFY_INVAL_ENTRY:
		return fuse_notify_inval_entry(fc, size, cs);

	case FUSE_NOTIFY_STORE:
		return fuse_notify_store(fc, size, cs);

	case FUSE_NOTIFY_RETRIEVE:
		return fuse_notify_retrieve(fc, size, cs);

	case FUSE_NOTIFY_DELETE:
		return fuse_notify_delete(fc, size, cs);

	case FUSE_NOTIFY_RESEND:
		return fuse_notify_resend(fc);

	case FUSE_NOTIFY_INC_EPOCH:
		return fuse_notify_inc_epoch(fc);

	case FUSE_NOTIFY_PRUNE:
		return fuse_notify_prune(fc, size, cs);

	default:
		return -EINVAL;
	}
}