inode.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/apfs/inode.c
 *
 * Copyright (C) 2018 Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
 */

#include <linux/slab.h>
#include <linux/buffer_head.h>
#include <linux/mpage.h>
#include <asm/div64.h>
#include "apfs.h"
#include "btree.h"
#include "dir.h"
#include "extents.h"
#include "inode.h"
#include "key.h"
#include "message.h"
#include "node.h"
#include "super.h"
#include "xattr.h"

static int apfs_readpage(struct file *file, struct page *page)
{
	return mpage_readpage(page, apfs_get_block);
}

#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 8, 0) /* Misses mpage_readpages() */

static void apfs_readahead(struct readahead_control *rac)
{
	mpage_readahead(rac, apfs_get_block);
}

#else /* LINUX_VERSION_CODE >= KERNEL_VERSION(5, 8, 0) */

static int apfs_readpages(struct file *file, struct address_space *mapping,
			  struct list_head *pages, unsigned int nr_pages)
{
	return mpage_readpages(mapping, pages, nr_pages, apfs_get_block);
}

#endif /* LINUX_VERSION_CODE >= KERNEL_VERSION(5, 8, 0) */

static sector_t apfs_bmap(struct address_space *mapping, sector_t block)
{
	return generic_block_bmap(mapping, block, apfs_get_block);
}

static const struct address_space_operations apfs_aops = {
	.readpage	= apfs_readpage,
#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 8, 0)
	.readahead	= apfs_readahead,
#else
	.readpages	= apfs_readpages,
#endif
	.bmap		= apfs_bmap,
};

/**
 * apfs_inode_from_query - Read the inode found by a successful query
 * @query:	the query that found the record
 * @inode:	vfs inode to be filled with the read data
 *
 * Reads the inode record into @inode and performs some basic sanity checks,
 * mostly as a protection against crafted filesystems.  Returns 0 on success
 * or a negative error code otherwise.
 */
static int apfs_inode_from_query(struct apfs_query *query, struct inode *inode)
{
	struct apfs_inode_info *ai = APFS_I(inode);
	struct apfs_inode_val *inode_val;
	struct apfs_dstream *dstream = NULL;
	struct apfs_xf_blob *xblob;
	struct apfs_x_field *xfield;
	char *raw = query->node->object.bh->b_data;
	int rest, i;
	u64 secs;

	if (query->len < sizeof(*inode_val))
		return -EFSCORRUPTED;

	inode_val = (struct apfs_inode_val *)(raw + query->off);

	ai->i_extent_id = le64_to_cpu(inode_val->private_id);
	inode->i_mode = le16_to_cpu(inode_val->mode);
	i_uid_write(inode, (uid_t)le32_to_cpu(inode_val->owner));
	i_gid_write(inode, (gid_t)le32_to_cpu(inode_val->group));

	if (S_ISREG(inode->i_mode) || S_ISLNK(inode->i_mode)) {
		/*
		 * It seems that hard links are only allowed for regular files,
		 * and perhaps for symlinks.
		 *
		 * Directory inodes don't store their link count, so to provide
		 * it we would have to actually count the subdirectories. The
		 * HFS/HFS+ modules just leave it at 1, and so do we, for now.
		 */
		set_nlink(inode, le32_to_cpu(inode_val->nlink));
	}

	/* APFS stores the time as unsigned nanoseconds since the epoch */
	secs = le64_to_cpu(inode_val->access_time);
	inode->i_atime.tv_nsec = do_div(secs, NSEC_PER_SEC);
	inode->i_atime.tv_sec = secs;
	secs = le64_to_cpu(inode_val->change_time);
	inode->i_ctime.tv_nsec = do_div(secs, NSEC_PER_SEC);
	inode->i_ctime.tv_sec = secs;
	secs = le64_to_cpu(inode_val->mod_time);
	inode->i_mtime.tv_nsec = do_div(secs, NSEC_PER_SEC);
	inode->i_mtime.tv_sec = secs;
	secs = le64_to_cpu(inode_val->create_time);
	ai->i_crtime.tv_nsec = do_div(secs, NSEC_PER_SEC);
	ai->i_crtime.tv_sec = secs;

	xblob = (struct apfs_xf_blob *) inode_val->xfields;
	xfield = (struct apfs_x_field *) xblob->xf_data;
	rest = query->len - (sizeof(*inode_val) + sizeof(*xblob));
	rest -= le16_to_cpu(xblob->xf_num_exts) * sizeof(xfield[0]);
	if (rest < 0)
		return -EFSCORRUPTED;
	for (i = 0; i < le16_to_cpu(xblob->xf_num_exts); ++i) {
		int attrlen;

		/* Attribute length is padded to a multiple of 8 */
		attrlen = round_up(le16_to_cpu(xfield[i].x_size), 8);
		if (attrlen > rest)
			break;
		if (xfield[i].x_type == APFS_INO_EXT_TYPE_DSTREAM) {
			/* The only optional attr we care about, for now */
			dstream = (struct apfs_dstream *)
					((char *)inode_val + query->len - rest);
			break;
		}
		rest -= attrlen;
	}

	if (dstream) {
		inode->i_size = le64_to_cpu(dstream->size);
		inode->i_blocks = le64_to_cpu(dstream->alloced_size) >> 9;
	} else {
		/*
		 * This inode is "empty", but it may actually hold compressed
		 * data in the named attribute com.apple.decmpfs, and sometimes
		 * in com.apple.ResourceFork
		 */
		inode->i_size = inode->i_blocks = 0;
	}

	return 0;
}

/**
 * apfs_inode_lookup - Lookup an inode record in the b-tree and read its data
 * @inode:	vfs inode to lookup and fill
 *
 * Queries the b-tree for the @inode->i_ino inode record and reads its data to
 * @inode.  Returns 0 on success or a negative error code otherwise.
 */
static int apfs_inode_lookup(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;
	struct apfs_sb_info *sbi = APFS_SB(sb);
	struct apfs_key key;
	struct apfs_query *query;
	u64 cnid = inode->i_ino;
	int ret;

	apfs_init_inode_key(cnid, &key);

	query = apfs_alloc_query(sbi->s_cat_root, NULL /* parent */);
	if (!query)
		return -ENOMEM;
	query->key = &key;
	query->flags |= APFS_QUERY_CAT | APFS_QUERY_EXACT;

	ret = apfs_btree_query(sb, &query);
	if (ret)
		goto done;

	ret = apfs_inode_from_query(query, inode);
	if (ret)
		apfs_alert(sb, "bad inode record for inode 0x%llx", cnid);

done:
	apfs_free_query(sb, query);
	return ret;
}

#if BITS_PER_LONG == 64
#define apfs_iget_locked iget_locked
#else /* 64-bit inode numbers may not fit in the vfs inode */

/**
 * apfs_test_inode - Check if the inode matches a 64-bit inode number
 * @inode:	inode to test
 * @cnid:	pointer to the inode number
 */
static int apfs_test_inode(struct inode *inode, void *cnid)
{
	struct apfs_inode_info *ai = APFS_I(inode);
	u64 *ino = cnid;

	return ai->i_ino == *ino;
}

/**
 * apfs_set_inode - Set a 64-bit inode number on the given inode
 * @inode:	inode to set
 * @cnid:	pointer to the inode number
 */
static int apfs_set_inode(struct inode *inode, void *cnid)
{
	struct apfs_inode_info *ai = APFS_I(inode);
	u64 *ino = cnid;

	ai->i_ino = *ino;
	inode->i_ino = *ino; /* Just discard the higher bits here... */
	return 0;
}

/**
 * apfs_iget_locked - Wrapper for iget5_locked()
 * @sb:		filesystem superblock
 * @cnid:	64-bit inode number
 *
 * Works the same as iget_locked(), but supports 64-bit inode numbers.
 */
static struct inode *apfs_iget_locked(struct super_block *sb, u64 cnid)
{
	return iget5_locked(sb, cnid, apfs_test_inode, apfs_set_inode, &cnid);
}

#endif /* BITS_PER_LONG == 64 */

/**
 * apfs_iget - Populate inode structures with metadata from disk
 * @sb:		filesystem superblock
 * @cnid:	inode number
 *
 * Populates the vfs inode and the corresponding apfs_inode_info structure.
 * Returns a pointer to the vfs inode in case of success, or an appropriate
 * error pointer otherwise.
 */
struct inode *apfs_iget(struct super_block *sb, u64 cnid)
{
	struct apfs_sb_info *sbi = APFS_SB(sb);
	struct inode *inode;
	int err;

	inode = apfs_iget_locked(sb, cnid);
	if (!inode)
		return ERR_PTR(-ENOMEM);
	if (!(inode->i_state & I_NEW))
		return inode;

	err = apfs_inode_lookup(inode);
	if (err) {
		iget_failed(inode);
		return ERR_PTR(err);
	}

	/* Allow the user to override the ownership */
	if (sbi->s_flags & APFS_UID_OVERRIDE)
		inode->i_uid = sbi->s_uid;
	if (sbi->s_flags & APFS_GID_OVERRIDE)
		inode->i_gid = sbi->s_gid;

	/* A lot of operations still missing, of course */
	if (S_ISREG(inode->i_mode)) {
		inode->i_op = &apfs_file_inode_operations;
		inode->i_fop = &apfs_file_operations;
		inode->i_mapping->a_ops = &apfs_aops;
	} else if (S_ISDIR(inode->i_mode)) {
		inode->i_op = &apfs_dir_inode_operations;
		inode->i_fop = &apfs_dir_operations;
	} else if (S_ISLNK(inode->i_mode)) {
		inode->i_op = &apfs_symlink_inode_operations;
	} else {
		inode->i_op = &apfs_special_inode_operations;
	}

	/* Inode flags are not important for now, leave them at 0 */
	unlock_new_inode(inode);
	return inode;
}

#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 11, 0) /* No statx yet... */

int apfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
		 struct kstat *stat)
{
	struct inode *inode = d_inode(dentry);

	generic_fillattr(inode, stat);
#if BITS_PER_LONG == 32
	stat->ino = ai->i_ino;
#endif /* BITS_PER_LONG == 32 */
	return 0;
}

#else /* LINUX_VERSION_CODE < KERNEL_VERSION(4, 11, 0) */

int apfs_getattr(const struct path *path, struct kstat *stat,
		 u32 request_mask, unsigned int query_flags)
{
	struct inode *inode = d_inode(path->dentry);
	struct apfs_inode_info *ai = APFS_I(inode);

	stat->result_mask |= STATX_BTIME;
	stat->btime = ai->i_crtime;

	if (apfs_xattr_get(inode, APFS_XATTR_NAME_COMPRESSED, NULL, 0) >= 0)
		stat->attributes |= STATX_ATTR_COMPRESSED;

	stat->attributes_mask |= STATX_ATTR_COMPRESSED;

	generic_fillattr(inode, stat);
#if BITS_PER_LONG == 32
	stat->ino = ai->i_ino;
#endif /* BITS_PER_LONG == 32 */
	return 0;
}

#endif /* LINUX_VERSION_CODE < KERNEL_VERSION(4, 11, 0) */