// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS filesystem directory editing
 *
 * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/pagemap.h>
#include <linux/iversion.h>
#include <linux/folio_queue.h>
#include "internal.h"
#include "xdr_fs.h"

/*
 * Find a number of contiguous clear bits in a directory block bitmask.
 *
 * There are 64 slots, which means we can load the entire bitmap into a
 * variable.  The first bit doesn't count as it corresponds to the block header
 * slot.  nr_slots is between 1 and 9.
 */
static int afs_find_contig_bits(union afs_xdr_dir_block *block, unsigned int nr_slots)
{
        u64 bitmap;
        u32 mask;
        int bit, n;

        bitmap  = (u64)block->hdr.bitmap[0] << 0 * 8;
        bitmap |= (u64)block->hdr.bitmap[1] << 1 * 8;
        bitmap |= (u64)block->hdr.bitmap[2] << 2 * 8;
        bitmap |= (u64)block->hdr.bitmap[3] << 3 * 8;
        bitmap |= (u64)block->hdr.bitmap[4] << 4 * 8;
        bitmap |= (u64)block->hdr.bitmap[5] << 5 * 8;
        bitmap |= (u64)block->hdr.bitmap[6] << 6 * 8;
        bitmap |= (u64)block->hdr.bitmap[7] << 7 * 8;
        bitmap >>= 1; /* The first entry is metadata */
        bit = 1;
        mask = (1 << nr_slots) - 1;

        do {
                if (sizeof(unsigned long) == 8)
                        n = ffz(bitmap);
                else
                        n = ((u32)bitmap) != 0 ?
                                ffz((u32)bitmap) :
                                ffz((u32)(bitmap >> 32)) + 32;
                bitmap >>= n;
                bit += n;

                if ((bitmap & mask) == 0) {
                        if (bit > 64 - nr_slots)
                                return -1;
                        return bit;
                }

                n = __ffs(bitmap);
                bitmap >>= n;
                bit += n;
        } while (bitmap);

        return -1;
}

/*
 * Set a number of contiguous bits in the directory block bitmap.
 */
static void afs_set_contig_bits(union afs_xdr_dir_block *block,
                                int bit, unsigned int nr_slots)
{
        u64 mask;

        mask = (1 << nr_slots) - 1;
        mask <<= bit;

        block->hdr.bitmap[0] |= (u8)(mask >> 0 * 8);
        block->hdr.bitmap[1] |= (u8)(mask >> 1 * 8);
        block->hdr.bitmap[2] |= (u8)(mask >> 2 * 8);
        block->hdr.bitmap[3] |= (u8)(mask >> 3 * 8);
        block->hdr.bitmap[4] |= (u8)(mask >> 4 * 8);
        block->hdr.bitmap[5] |= (u8)(mask >> 5 * 8);
        block->hdr.bitmap[6] |= (u8)(mask >> 6 * 8);
        block->hdr.bitmap[7] |= (u8)(mask >> 7 * 8);
}

/*
 * Clear a number of contiguous bits in the directory block bitmap.
 */
static void afs_clear_contig_bits(union afs_xdr_dir_block *block,
                                  int bit, unsigned int nr_slots)
{
        u64 mask;

        mask = (1 << nr_slots) - 1;
        mask <<= bit;

        block->hdr.bitmap[0] &= ~(u8)(mask >> 0 * 8);
        block->hdr.bitmap[1] &= ~(u8)(mask >> 1 * 8);
        block->hdr.bitmap[2] &= ~(u8)(mask >> 2 * 8);
        block->hdr.bitmap[3] &= ~(u8)(mask >> 3 * 8);
        block->hdr.bitmap[4] &= ~(u8)(mask >> 4 * 8);
        block->hdr.bitmap[5] &= ~(u8)(mask >> 5 * 8);
        block->hdr.bitmap[6] &= ~(u8)(mask >> 6 * 8);
        block->hdr.bitmap[7] &= ~(u8)(mask >> 7 * 8);
}

/*
 * Get a specific block, extending the directory storage to cover it as needed.
 */
static union afs_xdr_dir_block *afs_dir_get_block(struct afs_dir_iter *iter, size_t block)
{
        struct folio_queue *fq;
        struct afs_vnode *dvnode = iter->dvnode;
        struct folio *folio;
        size_t blpos = block * AFS_DIR_BLOCK_SIZE;
        size_t blend = (block + 1) * AFS_DIR_BLOCK_SIZE, fpos = iter->fpos;
        int ret;

        if (dvnode->directory_size < blend) {
                size_t cur_size = dvnode->directory_size;

                ret = netfs_alloc_folioq_buffer(
                        NULL, &dvnode->directory, &cur_size, blend,
                        mapping_gfp_mask(dvnode->netfs.inode.i_mapping));
                dvnode->directory_size = cur_size;
                if (ret < 0)
                        goto fail;
        }

        fq = iter->fq;
        if (!fq)
                fq = dvnode->directory;

        /* Search the folio queue for the folio containing the block... */
        for (; fq; fq = fq->next) {
                for (int s = iter->fq_slot; s < folioq_count(fq); s++) {
                        size_t fsize = folioq_folio_size(fq, s);

                        if (blend <= fpos + fsize) {
                                /* ... and then return the mapped block. */
                                folio = folioq_folio(fq, s);
                                if (WARN_ON_ONCE(folio_pos(folio) != fpos))
                                        goto fail;
                                iter->fq = fq;
                                iter->fq_slot = s;
                                iter->fpos = fpos;
                                return kmap_local_folio(folio, blpos - fpos);
                        }
                        fpos += fsize;
                }
                iter->fq_slot = 0;
        }

fail:
        iter->fq = NULL;
        iter->fq_slot = 0;
        afs_invalidate_dir(dvnode, afs_dir_invalid_edit_get_block);
        return NULL;
}

/*
 * Scan a directory block looking for a dirent of the right name.
 */
static int afs_dir_scan_block(const union afs_xdr_dir_block *block, const struct qstr *name,
                              unsigned int blocknum)
{
        const union afs_xdr_dirent *de;
        u64 bitmap;
        int d, len, n;

        _enter("");

        bitmap  = (u64)block->hdr.bitmap[0] << 0 * 8;
        bitmap |= (u64)block->hdr.bitmap[1] << 1 * 8;
        bitmap |= (u64)block->hdr.bitmap[2] << 2 * 8;
        bitmap |= (u64)block->hdr.bitmap[3] << 3 * 8;
        bitmap |= (u64)block->hdr.bitmap[4] << 4 * 8;
        bitmap |= (u64)block->hdr.bitmap[5] << 5 * 8;
        bitmap |= (u64)block->hdr.bitmap[6] << 6 * 8;
        bitmap |= (u64)block->hdr.bitmap[7] << 7 * 8;

        for (d = (blocknum == 0 ? AFS_DIR_RESV_BLOCKS0 : AFS_DIR_RESV_BLOCKS);
             d < AFS_DIR_SLOTS_PER_BLOCK;
             d++) {
                if (!((bitmap >> d) & 1))
                        continue;
                de = &block->dirents[d];
                if (de->u.valid != 1)
                        continue;

                /* The block was NUL-terminated by afs_dir_check_page(). */
                len = strlen(de->u.name);
                if (len == name->len &&
                    memcmp(de->u.name, name->name, name->len) == 0)
                        return d;

                n = round_up(12 + len + 1 + 4, AFS_DIR_DIRENT_SIZE);
                n /= AFS_DIR_DIRENT_SIZE;
                d += n - 1;
        }

        return -1;
}

/*
 * Initialise a new directory block.  Note that block 0 is special and contains
 * some extra metadata.
 */
static void afs_edit_init_block(union afs_xdr_dir_block *meta,
                                union afs_xdr_dir_block *block, int block_num)
{
        memset(block, 0, sizeof(*block));
        block->hdr.npages = htons(1);
        block->hdr.magic = AFS_DIR_MAGIC;
        block->hdr.bitmap[0] = 1;

        if (block_num == 0) {
                block->hdr.bitmap[0] = 0xff;
                block->hdr.bitmap[1] = 0x1f;
                memset(block->meta.alloc_ctrs,
                       AFS_DIR_SLOTS_PER_BLOCK,
                       sizeof(block->meta.alloc_ctrs));
                meta->meta.alloc_ctrs[0] =
                        AFS_DIR_SLOTS_PER_BLOCK - AFS_DIR_RESV_BLOCKS0;
        }

        if (block_num < AFS_DIR_BLOCKS_WITH_CTR)
                meta->meta.alloc_ctrs[block_num] =
                        AFS_DIR_SLOTS_PER_BLOCK - AFS_DIR_RESV_BLOCKS;
}

/*
 * Edit a directory's file data to add a new directory entry.  Doing this after
 * create, mkdir, symlink, link or rename if the data version number is
 * incremented by exactly one avoids the need to re-download the entire
 * directory contents.
 *
 * The caller must hold the inode locked.
 */
void afs_edit_dir_add(struct afs_vnode *vnode,
                      const struct qstr *name, struct afs_fid *new_fid,
                      enum afs_edit_dir_reason why)
{
        union afs_xdr_dir_block *meta, *block;
        union afs_xdr_dirent *de;
        struct afs_dir_iter iter = { .dvnode = vnode };
        unsigned int nr_blocks, b, entry;
        loff_t i_size;
        int slot;

        _enter(",,{%d,%s},", name->len, name->name);

        i_size = i_size_read(&vnode->netfs.inode);
        if (i_size > AFS_DIR_BLOCK_SIZE * AFS_DIR_MAX_BLOCKS ||
            (i_size & (AFS_DIR_BLOCK_SIZE - 1))) {
                afs_invalidate_dir(vnode, afs_dir_invalid_edit_add_bad_size);
                return;
        }

        meta = afs_dir_get_block(&iter, 0);
        if (!meta)
                return;

        /* Work out how many slots we're going to need. */
        iter.nr_slots = afs_dir_calc_slots(name->len);

        if (i_size == 0)
                goto new_directory;
        nr_blocks = i_size / AFS_DIR_BLOCK_SIZE;

        /* Find a block that has sufficient slots available.  Each folio
         * contains two or more directory blocks.
         */
        for (b = 0; b < nr_blocks + 1; b++) {
                /* If the directory extended into a new folio, then we need to
                 * tack a new folio on the end.
                 */
                if (nr_blocks >= AFS_DIR_MAX_BLOCKS)
                        goto error_too_many_blocks;

                /* Lower dir blocks have a counter in the header we can check. */
                if (b < AFS_DIR_BLOCKS_WITH_CTR &&
                    meta->meta.alloc_ctrs[b] < iter.nr_slots)
                        continue;

                block = afs_dir_get_block(&iter, b);
                if (!block)
                        goto error;

                /* Abandon the edit if we got a callback break. */
                if (!test_bit(AFS_VNODE_DIR_VALID, &vnode->flags))
                        goto already_invalidated;

                _debug("block %u: %2u %3u %u",
                       b,
                       (b < AFS_DIR_BLOCKS_WITH_CTR) ? meta->meta.alloc_ctrs[b] : 99,
                       ntohs(block->hdr.npages),
                       ntohs(block->hdr.magic));

                /* Initialise the block if necessary. */
                if (b == nr_blocks) {
                        _debug("init %u", b);
                        afs_edit_init_block(meta, block, b);
                        afs_set_i_size(vnode, (b + 1) * AFS_DIR_BLOCK_SIZE);
                }

                /* We need to try and find one or more consecutive slots to
                 * hold the entry.
                 */
                slot = afs_find_contig_bits(block, iter.nr_slots);
                if (slot >= 0) {
                        _debug("slot %u", slot);
                        goto found_space;
                }

                kunmap_local(block);
        }

        /* There are no spare slots of sufficient size, yet the operation
         * succeeded.  Download the directory again.
         */
        trace_afs_edit_dir(vnode, why, afs_edit_dir_create_nospc, 0, 0, 0, 0, name->name);
        afs_invalidate_dir(vnode, afs_dir_invalid_edit_add_no_slots);
        goto out_unmap;

new_directory:
        afs_edit_init_block(meta, meta, 0);
        i_size = AFS_DIR_BLOCK_SIZE;
        afs_set_i_size(vnode, i_size);
        slot = AFS_DIR_RESV_BLOCKS0;
        block = afs_dir_get_block(&iter, 0);
        nr_blocks = 1;
        b = 0;

found_space:
        /* Set the dirent slot. */
        trace_afs_edit_dir(vnode, why, afs_edit_dir_create, b, slot,
                           new_fid->vnode, new_fid->unique, name->name);
        de = &block->dirents[slot];
        de->u.valid     = 1;
        de->u.unused[0] = 0;
        de->u.hash_next = 0; // TODO: Really need to maintain this
        de->u.vnode     = htonl(new_fid->vnode);
        de->u.unique    = htonl(new_fid->unique);
        memcpy(de->u.name, name->name, name->len + 1);
        de->u.name[name->len] = 0;

        /* Adjust the bitmap. */
        afs_set_contig_bits(block, slot, iter.nr_slots);

        /* Adjust the allocation counter. */
        if (b < AFS_DIR_BLOCKS_WITH_CTR)
                meta->meta.alloc_ctrs[b] -= iter.nr_slots;

        /* Adjust the hash chain. */
        entry = b * AFS_DIR_SLOTS_PER_BLOCK + slot;
        iter.bucket = afs_dir_hash_name(name);
        de->u.hash_next = meta->meta.hashtable[iter.bucket];
        meta->meta.hashtable[iter.bucket] = htons(entry);
        kunmap_local(block);

        inode_inc_iversion_raw(&vnode->netfs.inode);
        afs_stat_v(vnode, n_dir_cr);
        _debug("Insert %s in %u[%u]", name->name, b, slot);

        netfs_single_mark_inode_dirty(&vnode->netfs.inode);

out_unmap:
        kunmap_local(meta);
        _leave("");
        return;

already_invalidated:
        trace_afs_edit_dir(vnode, why, afs_edit_dir_create_inval, 0, 0, 0, 0, name->name);
        kunmap_local(block);
        goto out_unmap;

error_too_many_blocks:
        afs_invalidate_dir(vnode, afs_dir_invalid_edit_add_too_many_blocks);
error:
        trace_afs_edit_dir(vnode, why, afs_edit_dir_create_error, 0, 0, 0, 0, name->name);
        goto out_unmap;
}

/*
 * Edit a directory's file data to remove a new directory entry.  Doing this
 * after unlink, rmdir or rename if the data version number is incremented by
 * exactly one avoids the need to re-download the entire directory contents.
 *
 * The caller must hold the inode locked.
 */
void afs_edit_dir_remove(struct afs_vnode *vnode,
                         const struct qstr *name, enum afs_edit_dir_reason why)
{
        union afs_xdr_dir_block *meta, *block, *pblock;
        union afs_xdr_dirent *de, *pde;
        struct afs_dir_iter iter = { .dvnode = vnode };
        struct afs_fid fid;
        unsigned int b, slot, entry;
        loff_t i_size;
        __be16 next;
        int found;

        _enter(",,{%d,%s},", name->len, name->name);

        i_size = i_size_read(&vnode->netfs.inode);
        if (i_size < AFS_DIR_BLOCK_SIZE ||
            i_size > AFS_DIR_BLOCK_SIZE * AFS_DIR_MAX_BLOCKS ||
            (i_size & (AFS_DIR_BLOCK_SIZE - 1))) {
                afs_invalidate_dir(vnode, afs_dir_invalid_edit_rem_bad_size);
                return;
        }

        if (!afs_dir_init_iter(&iter, name))
                return;

        meta = afs_dir_find_block(&iter, 0);
        if (!meta)
                return;

        /* Find the entry in the blob. */
        found = afs_dir_search_bucket(&iter, name, &fid);
        if (found < 0) {
                /* Didn't find the dirent to clobber.  Re-download. */
                trace_afs_edit_dir(vnode, why, afs_edit_dir_delete_noent,
                                   0, 0, 0, 0, name->name);
                afs_invalidate_dir(vnode, afs_dir_invalid_edit_rem_wrong_name);
                goto out_unmap;
        }

        entry = found;
        b    = entry / AFS_DIR_SLOTS_PER_BLOCK;
        slot = entry % AFS_DIR_SLOTS_PER_BLOCK;

        block = afs_dir_find_block(&iter, b);
        if (!block)
                goto error;
        if (!test_bit(AFS_VNODE_DIR_VALID, &vnode->flags))
                goto already_invalidated;

        /* Check and clear the entry. */
        de = &block->dirents[slot];
        if (de->u.valid != 1)
                goto error_unmap;

        trace_afs_edit_dir(vnode, why, afs_edit_dir_delete, b, slot,
                           ntohl(de->u.vnode), ntohl(de->u.unique),
                           name->name);

        /* Adjust the bitmap. */
        afs_clear_contig_bits(block, slot, iter.nr_slots);

        /* Adjust the allocation counter. */
        if (b < AFS_DIR_BLOCKS_WITH_CTR)
                meta->meta.alloc_ctrs[b] += iter.nr_slots;

        /* Clear the constituent entries. */
        next = de->u.hash_next;
        memset(de, 0, sizeof(*de) * iter.nr_slots);
        kunmap_local(block);

        /* Adjust the hash chain: if iter->prev_entry is 0, the hashtable head
         * index is previous; otherwise it's slot number of the previous entry.
         */
        if (!iter.prev_entry) {
                __be16 prev_next = meta->meta.hashtable[iter.bucket];

                if (unlikely(prev_next != htons(entry))) {
                        pr_warn("%llx:%llx:%x: not head of chain b=%x p=%x,%x e=%x %*s",
                                vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique,
                                iter.bucket, iter.prev_entry, prev_next, entry,
                                name->len, name->name);
                        goto error;
                }
                meta->meta.hashtable[iter.bucket] = next;
        } else {
                unsigned int pb = iter.prev_entry / AFS_DIR_SLOTS_PER_BLOCK;
                unsigned int ps = iter.prev_entry % AFS_DIR_SLOTS_PER_BLOCK;
                __be16 prev_next;

                pblock = afs_dir_find_block(&iter, pb);
                if (!pblock)
                        goto error;
                pde = &pblock->dirents[ps];
                prev_next = pde->u.hash_next;
                if (prev_next != htons(entry)) {
                        kunmap_local(pblock);
                        pr_warn("%llx:%llx:%x: not prev in chain b=%x p=%x,%x e=%x %*s",
                                vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique,
                                iter.bucket, iter.prev_entry, prev_next, entry,
                                name->len, name->name);
                        goto error;
                }
                pde->u.hash_next = next;
                kunmap_local(pblock);
        }

        netfs_single_mark_inode_dirty(&vnode->netfs.inode);

        inode_set_iversion_raw(&vnode->netfs.inode, vnode->status.data_version);
        afs_stat_v(vnode, n_dir_rm);
        _debug("Remove %s from %u[%u]", name->name, b, slot);

out_unmap:
        kunmap_local(meta);
        _leave("");
        return;

already_invalidated:
        kunmap_local(block);
        trace_afs_edit_dir(vnode, why, afs_edit_dir_delete_inval,
                           0, 0, 0, 0, name->name);
        goto out_unmap;

error_unmap:
        kunmap_local(block);
error:
        trace_afs_edit_dir(vnode, why, afs_edit_dir_delete_error,
                           0, 0, 0, 0, name->name);
        goto out_unmap;
}

/*
 * Edit an entry in a directory to update the vnode it refers to.  This is also
 * used to update the ".." entry in a directory.
 */
void afs_edit_dir_update(struct afs_vnode *vnode, const struct qstr *name,
                         struct afs_vnode *new_dvnode, enum afs_edit_dir_reason why)
{
        union afs_xdr_dir_block *block;
        union afs_xdr_dirent *de;
        struct afs_dir_iter iter = { .dvnode = vnode };
        unsigned int nr_blocks, b;
        loff_t i_size;
        int slot;

        _enter("");

        i_size = i_size_read(&vnode->netfs.inode);
        if (i_size < AFS_DIR_BLOCK_SIZE) {
                afs_invalidate_dir(vnode, afs_dir_invalid_edit_upd_bad_size);
                return;
        }

        nr_blocks = i_size / AFS_DIR_BLOCK_SIZE;

        /* Find a block that has sufficient slots available.  Each folio
         * contains two or more directory blocks.
         */
        for (b = 0; b < nr_blocks; b++) {
                block = afs_dir_get_block(&iter, b);
                if (!block)
                        goto error;

                /* Abandon the edit if we got a callback break. */
                if (!test_bit(AFS_VNODE_DIR_VALID, &vnode->flags))
                        goto already_invalidated;

                slot = afs_dir_scan_block(block, name, b);
                if (slot >= 0)
                        goto found_dirent;

                kunmap_local(block);
        }

        /* Didn't find the dirent to clobber.  Download the directory again. */
        trace_afs_edit_dir(vnode, why, afs_edit_dir_update_nodd,
                           0, 0, 0, 0, name->name);
        afs_invalidate_dir(vnode, afs_dir_invalid_edit_upd_no_dd);
        goto out;

found_dirent:
        de = &block->dirents[slot];
        de->u.vnode  = htonl(new_dvnode->fid.vnode);
        de->u.unique = htonl(new_dvnode->fid.unique);

        trace_afs_edit_dir(vnode, why, afs_edit_dir_update_dd, b, slot,
                           ntohl(de->u.vnode), ntohl(de->u.unique), name->name);

        kunmap_local(block);
        netfs_single_mark_inode_dirty(&vnode->netfs.inode);
        inode_set_iversion_raw(&vnode->netfs.inode, vnode->status.data_version);

out:
        _leave("");
        return;

already_invalidated:
        kunmap_local(block);
        trace_afs_edit_dir(vnode, why, afs_edit_dir_update_inval,
                           0, 0, 0, 0, name->name);
        goto out;

error:
        trace_afs_edit_dir(vnode, why, afs_edit_dir_update_error,
                           0, 0, 0, 0, name->name);
        goto out;
}

/*
 * Initialise a new directory.  We need to fill in the "." and ".." entries.
 */
void afs_mkdir_init_dir(struct afs_vnode *dvnode, struct afs_vnode *parent_dvnode)
{
        union afs_xdr_dir_block *meta;
        struct afs_dir_iter iter = { .dvnode = dvnode };
        union afs_xdr_dirent *de;
        unsigned int slot = AFS_DIR_RESV_BLOCKS0;
        loff_t i_size;

        i_size = i_size_read(&dvnode->netfs.inode);
        if (i_size != AFS_DIR_BLOCK_SIZE) {
                afs_invalidate_dir(dvnode, afs_dir_invalid_edit_add_bad_size);
                return;
        }

        meta = afs_dir_get_block(&iter, 0);
        if (!meta)
                return;

        afs_edit_init_block(meta, meta, 0);

        de = &meta->dirents[slot];
        de->u.valid  = 1;
        de->u.vnode  = htonl(dvnode->fid.vnode);
        de->u.unique = htonl(dvnode->fid.unique);
        memcpy(de->u.name, ".", 2);
        trace_afs_edit_dir(dvnode, afs_edit_dir_for_mkdir, afs_edit_dir_mkdir, 0, slot,
                           dvnode->fid.vnode, dvnode->fid.unique, ".");
        slot++;

        de = &meta->dirents[slot];
        de->u.valid  = 1;
        de->u.vnode  = htonl(parent_dvnode->fid.vnode);
        de->u.unique = htonl(parent_dvnode->fid.unique);
        memcpy(de->u.name, "..", 3);
        trace_afs_edit_dir(dvnode, afs_edit_dir_for_mkdir, afs_edit_dir_mkdir, 0, slot,
                           parent_dvnode->fid.vnode, parent_dvnode->fid.unique, "..");

        afs_set_contig_bits(meta, AFS_DIR_RESV_BLOCKS0, 2);
        meta->meta.alloc_ctrs[0] -= 2;
        kunmap_local(meta);

        netfs_single_mark_inode_dirty(&dvnode->netfs.inode);
        set_bit(AFS_VNODE_DIR_VALID, &dvnode->flags);
        set_bit(AFS_VNODE_DIR_READ, &dvnode->flags);
}