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/*

 *  linux/fs/ext4/ialloc.c

 *

 * Copyright (C) 1992, 1993, 1994, 1995

 * Remy Card (card@masi.ibp.fr)

 * Laboratoire MASI - Institut Blaise Pascal

 * Universite Pierre et Marie Curie (Paris VI)

 *

 *  BSD ufs-inspired inode and directory allocation by

 *  Stephen Tweedie (sct@redhat.com), 1993

 *  Big-endian to little-endian byte-swapping/bitmaps by

 *        David S. Miller (davem@caip.rutgers.edu), 1995

 */

#include <linux/time.h>

#include <linux/fs.h>

#include <linux/jbd2.h>

#include <linux/ext4_fs.h>

#include <linux/ext4_jbd2.h>

#include <linux/stat.h>

#include <linux/string.h>

#include <linux/quotaops.h>

#include <linux/buffer_head.h>

#include <linux/random.h>

#include <linux/bitops.h>

#include <linux/blkdev.h>

#include <asm/byteorder.h>

#include "xattr.h"

#include "acl.h"

#include "group.h"

/*

 * ialloc.c contains the inodes allocation and deallocation routines

 */

/*

 * The free inodes are managed by bitmaps.  A file system contains several

 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap

 * block for inodes, N blocks for the inode table and data blocks.

 *

 * The file system contains group descriptors which are located after the

 * super block.  Each descriptor contains the number of the bitmap block and

 * the free blocks count in the block.

 */

/*

 * To avoid calling the atomic setbit hundreds or thousands of times, we only

 * need to use it within a single byte (to ensure we get endianness right).

 * We can use memset for the rest of the bitmap as there are no other users.

 */

void mark_bitmap_end(int start_bit, int end_bit, char *bitmap)

{

        int i;

        if (start_bit >= end_bit)

                return;

        ext4_debug("mark end bits +%d through +%d used\n", start_bit, end_bit);

        for (i = start_bit; i < ((start_bit + 7) & ~7UL); i++)

                ext4_set_bit(i, bitmap);

        if (i < end_bit)

                memset(bitmap + (i >> 3), 0xff, (end_bit - i) >> 3);

}

/* Initializes an uninitialized inode bitmap */

unsigned ext4_init_inode_bitmap(struct super_block *sb,

                                struct buffer_head *bh, int block_group,

                                struct ext4_group_desc *gdp)

{

        struct ext4_sb_info *sbi = EXT4_SB(sb);

        J_ASSERT_BH(bh, buffer_locked(bh));

        /* If checksum is bad mark all blocks and inodes use to prevent

         * allocation, essentially implementing a per-group read-only flag. */

        if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {

                ext4_error(sb, __FUNCTION__, "Checksum bad for group %u\n",

                           block_group);

                gdp->bg_free_blocks_count = 0;

                gdp->bg_free_inodes_count = 0;

                gdp->bg_itable_unused = 0;

                memset(bh->b_data, 0xff, sb->s_blocksize);

                return 0;

        }

        memset(bh->b_data, 0, (EXT4_INODES_PER_GROUP(sb) + 7) / 8);

        mark_bitmap_end(EXT4_INODES_PER_GROUP(sb), EXT4_BLOCKS_PER_GROUP(sb),

                        bh->b_data);

        return EXT4_INODES_PER_GROUP(sb);

}

/*

 * Read the inode allocation bitmap for a given block_group, reading

 * into the specified slot in the superblock's bitmap cache.

 *

 * Return buffer_head of bitmap on success or NULL.

 */

static struct buffer_head *

read_inode_bitmap(struct super_block * sb, unsigned long block_group)

{

        struct ext4_group_desc *desc;

        struct buffer_head *bh = NULL;

        desc = ext4_get_group_desc(sb, block_group, NULL);

        if (!desc)

                goto error_out;

        if (desc->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {

                bh = sb_getblk(sb, ext4_inode_bitmap(sb, desc));

                if (!buffer_uptodate(bh)) {

                        lock_buffer(bh);

                        if (!buffer_uptodate(bh)) {

                                ext4_init_inode_bitmap(sb, bh, block_group,

                                                       desc);

                                set_buffer_uptodate(bh);

                        }

                        unlock_buffer(bh);

                }

        } else {

                bh = sb_bread(sb, ext4_inode_bitmap(sb, desc));

        }

        if (!bh)

                ext4_error(sb, "read_inode_bitmap",

                            "Cannot read inode bitmap - "

                            "block_group = %lu, inode_bitmap = %llu",

                            block_group, ext4_inode_bitmap(sb, desc));

error_out:

        return bh;

}

/*

 * NOTE! When we get the inode, we're the only people

 * that have access to it, and as such there are no

 * race conditions we have to worry about. The inode

 * is not on the hash-lists, and it cannot be reached

 * through the filesystem because the directory entry

 * has been deleted earlier.

 *

 * HOWEVER: we must make sure that we get no aliases,

 * which means that we have to call "clear_inode()"

 * _before_ we mark the inode not in use in the inode

 * bitmaps. Otherwise a newly created file might use

 * the same inode number (not actually the same pointer

 * though), and then we'd have two inodes sharing the

 * same inode number and space on the harddisk.

 */

void ext4_free_inode (handle_t *handle, struct inode * inode)

{

        struct super_block * sb = inode->i_sb;

        int is_directory;

        unsigned long ino;

        struct buffer_head *bitmap_bh = NULL;

        struct buffer_head *bh2;

        unsigned long block_group;

        unsigned long bit;

        struct ext4_group_desc * gdp;

        struct ext4_super_block * es;

        struct ext4_sb_info *sbi;

        int fatal = 0, err;

        if (atomic_read(&inode->i_count) > 1) {

                printk ("ext4_free_inode: inode has count=%d\n",

                                        atomic_read(&inode->i_count));

                return;

        }

        if (inode->i_nlink) {

                printk ("ext4_free_inode: inode has nlink=%d\n",

                        inode->i_nlink);

                return;

        }

        if (!sb) {

                printk("ext4_free_inode: inode on nonexistent device\n");

                return;

        }

        sbi = EXT4_SB(sb);

        ino = inode->i_ino;

        ext4_debug ("freeing inode %lu\n", ino);

        /*

         * Note: we must free any quota before locking the superblock,

         * as writing the quota to disk may need the lock as well.

         */

        DQUOT_INIT(inode);

        ext4_xattr_delete_inode(handle, inode);

        DQUOT_FREE_INODE(inode);

        DQUOT_DROP(inode);

        is_directory = S_ISDIR(inode->i_mode);

        /* Do this BEFORE marking the inode not in use or returning an error */

        clear_inode (inode);

        es = EXT4_SB(sb)->s_es;

        if (ino < EXT4_FIRST_INO(sb) || ino > le32_to_cpu(es->s_inodes_count)) {

                ext4_error (sb, "ext4_free_inode",

                            "reserved or nonexistent inode %lu", ino);

                goto error_return;

        }

        block_group = (ino - 1) / EXT4_INODES_PER_GROUP(sb);

        bit = (ino - 1) % EXT4_INODES_PER_GROUP(sb);

        bitmap_bh = read_inode_bitmap(sb, block_group);

        if (!bitmap_bh)

                goto error_return;

        BUFFER_TRACE(bitmap_bh, "get_write_access");

        fatal = ext4_journal_get_write_access(handle, bitmap_bh);

        if (fatal)

                goto error_return;

        /* Ok, now we can actually update the inode bitmaps.. */

        if (!ext4_clear_bit_atomic(sb_bgl_lock(sbi, block_group),

                                        bit, bitmap_bh->b_data))

                ext4_error (sb, "ext4_free_inode",

                              "bit already cleared for inode %lu", ino);

        else {

                gdp = ext4_get_group_desc (sb, block_group, &bh2);

                BUFFER_TRACE(bh2, "get_write_access");

                fatal = ext4_journal_get_write_access(handle, bh2);

                if (fatal) goto error_return;

                if (gdp) {

                        spin_lock(sb_bgl_lock(sbi, block_group));

                        gdp->bg_free_inodes_count = cpu_to_le16(

                                le16_to_cpu(gdp->bg_free_inodes_count) + 1);

                        if (is_directory)

                                gdp->bg_used_dirs_count = cpu_to_le16(

                                  le16_to_cpu(gdp->bg_used_dirs_count) - 1);

                        gdp->bg_checksum = ext4_group_desc_csum(sbi,

                                                        block_group, gdp);

                        spin_unlock(sb_bgl_lock(sbi, block_group));

                        percpu_counter_inc(&sbi->s_freeinodes_counter);

                        if (is_directory)

                                percpu_counter_dec(&sbi->s_dirs_counter);

                }

                BUFFER_TRACE(bh2, "call ext4_journal_dirty_metadata");

                err = ext4_journal_dirty_metadata(handle, bh2);

                if (!fatal) fatal = err;

        }

        BUFFER_TRACE(bitmap_bh, "call ext4_journal_dirty_metadata");

        err = ext4_journal_dirty_metadata(handle, bitmap_bh);

        if (!fatal)

                fatal = err;

        sb->s_dirt = 1;

error_return:

        brelse(bitmap_bh);

        ext4_std_error(sb, fatal);

}

/*

 * There are two policies for allocating an inode.  If the new inode is

 * a directory, then a forward search is made for a block group with both

 * free space and a low directory-to-inode ratio; if that fails, then of

 * the groups with above-average free space, that group with the fewest

 * directories already is chosen.

 *

 * For other inodes, search forward from the parent directory\'s block

 * group to find a free inode.

 */

static int find_group_dir(struct super_block *sb, struct inode *parent)

{

        int ngroups = EXT4_SB(sb)->s_groups_count;

        unsigned int freei, avefreei;

        struct ext4_group_desc *desc, *best_desc = NULL;

        int group, best_group = -1;

        freei = percpu_counter_read_positive(&EXT4_SB(sb)->s_freeinodes_counter);

        avefreei = freei / ngroups;

        for (group = 0; group < ngroups; group++) {

                desc = ext4_get_group_desc (sb, group, NULL);

                if (!desc || !desc->bg_free_inodes_count)

                        continue;

                if (le16_to_cpu(desc->bg_free_inodes_count) < avefreei)

                        continue;

                if (!best_desc ||

                    (le16_to_cpu(desc->bg_free_blocks_count) >

                     le16_to_cpu(best_desc->bg_free_blocks_count))) {

                        best_group = group;

                        best_desc = desc;

                }

        }

        return best_group;

}

/*

 * Orlov's allocator for directories.

 *

 * We always try to spread first-level directories.

 *

 * If there are blockgroups with both free inodes and free blocks counts

 * not worse than average we return one with smallest directory count.

 * Otherwise we simply return a random group.

 *

 * For the rest rules look so:

 *

 * It's OK to put directory into a group unless

 * it has too many directories already (max_dirs) or

 * it has too few free inodes left (min_inodes) or

 * it has too few free blocks left (min_blocks) or

 * it's already running too large debt (max_debt).

 * Parent's group is prefered, if it doesn't satisfy these

 * conditions we search cyclically through the rest. If none

 * of the groups look good we just look for a group with more

 * free inodes than average (starting at parent's group).

 *

 * Debt is incremented each time we allocate a directory and decremented

 * when we allocate an inode, within 0--255.

 */

#define INODE_COST 64

#define BLOCK_COST 256

static int find_group_orlov(struct super_block *sb, struct inode *parent)

{

        int parent_group = EXT4_I(parent)->i_block_group;

        struct ext4_sb_info *sbi = EXT4_SB(sb);

        struct ext4_super_block *es = sbi->s_es;

        int ngroups = sbi->s_groups_count;

        int inodes_per_group = EXT4_INODES_PER_GROUP(sb);

        unsigned int freei, avefreei;

        ext4_fsblk_t freeb, avefreeb;

        ext4_fsblk_t blocks_per_dir;

        unsigned int ndirs;

        int max_debt, max_dirs, min_inodes;

        ext4_grpblk_t min_blocks;

        int group = -1, i;

        struct ext4_group_desc *desc;

        freei = percpu_counter_read_positive(&sbi->s_freeinodes_counter);

        avefreei = freei / ngroups;

        freeb = percpu_counter_read_positive(&sbi->s_freeblocks_counter);

        avefreeb = freeb;

        do_div(avefreeb, ngroups);

        ndirs = percpu_counter_read_positive(&sbi->s_dirs_counter);

        if ((parent == sb->s_root->d_inode) ||

            (EXT4_I(parent)->i_flags & EXT4_TOPDIR_FL)) {

                int best_ndir = inodes_per_group;

                int best_group = -1;

                get_random_bytes(&group, sizeof(group));

                parent_group = (unsigned)group % ngroups;

                for (i = 0; i < ngroups; i++) {

                        group = (parent_group + i) % ngroups;

                        desc = ext4_get_group_desc (sb, group, NULL);

                        if (!desc || !desc->bg_free_inodes_count)

                                continue;

                        if (le16_to_cpu(desc->bg_used_dirs_count) >= best_ndir)

                                continue;

                        if (le16_to_cpu(desc->bg_free_inodes_count) < avefreei)

                                continue;

                        if (le16_to_cpu(desc->bg_free_blocks_count) < avefreeb)

                                continue;

                        best_group = group;

                        best_ndir = le16_to_cpu(desc->bg_used_dirs_count);

                }

                if (best_group >= 0)

                        return best_group;

                goto fallback;

        }

        blocks_per_dir = ext4_blocks_count(es) - freeb;

        do_div(blocks_per_dir, ndirs);

        max_dirs = ndirs / ngroups + inodes_per_group / 16;

        min_inodes = avefreei - inodes_per_group / 4;

        min_blocks = avefreeb - EXT4_BLOCKS_PER_GROUP(sb) / 4;

        max_debt = EXT4_BLOCKS_PER_GROUP(sb);

        max_debt /= max_t(int, blocks_per_dir, BLOCK_COST);

        if (max_debt * INODE_COST > inodes_per_group)

                max_debt = inodes_per_group / INODE_COST;

        if (max_debt > 255)

                max_debt = 255;

        if (max_debt == 0)

                max_debt = 1;

        for (i = 0; i < ngroups; i++) {

                group = (parent_group + i) % ngroups;

                desc = ext4_get_group_desc (sb, group, NULL);

                if (!desc || !desc->bg_free_inodes_count)

                        continue;

                if (le16_to_cpu(desc->bg_used_dirs_count) >= max_dirs)

                        continue;

                if (le16_to_cpu(desc->bg_free_inodes_count) < min_inodes)

                        continue;

                if (le16_to_cpu(desc->bg_free_blocks_count) < min_blocks)

                        continue;

                return group;

        }

fallback:

        for (i = 0; i < ngroups; i++) {

                group = (parent_group + i) % ngroups;

                desc = ext4_get_group_desc (sb, group, NULL);

                if (!desc || !desc->bg_free_inodes_count)

                        continue;

                if (le16_to_cpu(desc->bg_free_inodes_count) >= avefreei)

                        return group;

        }

        if (avefreei) {

                /*

                 * The free-inodes counter is approximate, and for really small

                 * filesystems the above test can fail to find any blockgroups

                 */

                avefreei = 0;

                goto fallback;

        }

        return -1;

}

static int find_group_other(struct super_block *sb, struct inode *parent)

{

        int parent_group = EXT4_I(parent)->i_block_group;

        int ngroups = EXT4_SB(sb)->s_groups_count;

        struct ext4_group_desc *desc;

        int group, i;

        /*

         * Try to place the inode in its parent directory

         */

        group = parent_group;

        desc = ext4_get_group_desc (sb, group, NULL);

        if (desc && le16_to_cpu(desc->bg_free_inodes_count) &&

                        le16_to_cpu(desc->bg_free_blocks_count))

                return group;

        /*

         * We're going to place this inode in a different blockgroup from its

         * parent.  We want to cause files in a common directory to all land in

         * the same blockgroup.  But we want files which are in a different

         * directory which shares a blockgroup with our parent to land in a

         * different blockgroup.

         *

         * So add our directory's i_ino into the starting point for the hash.

         */

        group = (group + parent->i_ino) % ngroups;

        /*

         * Use a quadratic hash to find a group with a free inode and some free

         * blocks.

         */

        for (i = 1; i < ngroups; i <<= 1) {

                group += i;

                if (group >= ngroups)

                        group -= ngroups;

                desc = ext4_get_group_desc (sb, group, NULL);

                if (desc && le16_to_cpu(desc->bg_free_inodes_count) &&

                                le16_to_cpu(desc->bg_free_blocks_count))

                        return group;

        }

        /*

         * That failed: try linear search for a free inode, even if that group

         * has no free blocks.

         */

        group = parent_group;

        for (i = 0; i < ngroups; i++) {

                if (++group >= ngroups)

                        group = 0;

                desc = ext4_get_group_desc (sb, group, NULL);

                if (desc && le16_to_cpu(desc->bg_free_inodes_count))

                        return group;

        }

        return -1;

}

/*

 * There are two policies for allocating an inode.  If the new inode is

 * a directory, then a forward search is made for a block group with both

 * free space and a low directory-to-inode ratio; if that fails, then of

 * the groups with above-average free space, that group with the fewest

 * directories already is chosen.

 *

 * For other inodes, search forward from the parent directory's block

 * group to find a free inode.

 */

struct inode *ext4_new_inode(handle_t *handle, struct inode * dir, int mode)

{

        struct super_block *sb;

        struct buffer_head *bitmap_bh = NULL;

        struct buffer_head *bh2;

        int group;

        unsigned long ino = 0;

        struct inode * inode;

        struct ext4_group_desc * gdp = NULL;

        struct ext4_super_block * es;

        struct ext4_inode_info *ei;

        struct ext4_sb_info *sbi;

        int err = 0;

        struct inode *ret;

        int i, free = 0;

        /* Cannot create files in a deleted directory */

        if (!dir || !dir->i_nlink)

                return ERR_PTR(-EPERM);

        sb = dir->i_sb;

        inode = new_inode(sb);

        if (!inode)

                return ERR_PTR(-ENOMEM);

        ei = EXT4_I(inode);

        sbi = EXT4_SB(sb);

        es = sbi->s_es;

        if (S_ISDIR(mode)) {

                if (test_opt (sb, OLDALLOC))

                        group = find_group_dir(sb, dir);

                else

                        group = find_group_orlov(sb, dir);

        } else

                group = find_group_other(sb, dir);

        err = -ENOSPC;

        if (group == -1)

                goto out;

        for (i = 0; i < sbi->s_groups_count; i++) {

                err = -EIO;

                gdp = ext4_get_group_desc(sb, group, &bh2);

                if (!gdp)

                        goto fail;

                brelse(bitmap_bh);

                bitmap_bh = read_inode_bitmap(sb, group);

                if (!bitmap_bh)

                        goto fail;

                ino = 0;

repeat_in_this_group:

                ino = ext4_find_next_zero_bit((unsigned long *)

                                bitmap_bh->b_data, EXT4_INODES_PER_GROUP(sb), ino);

                if (ino < EXT4_INODES_PER_GROUP(sb)) {

                        BUFFER_TRACE(bitmap_bh, "get_write_access");

                        err = ext4_journal_get_write_access(handle, bitmap_bh);

                        if (err)

                                goto fail;

                        if (!ext4_set_bit_atomic(sb_bgl_lock(sbi, group),

                                                ino, bitmap_bh->b_data)) {

                                /* we won it */

                                BUFFER_TRACE(bitmap_bh,

                                        "call ext4_journal_dirty_metadata");

                                err = ext4_journal_dirty_metadata(handle,

                                                                bitmap_bh);

                                if (err)

                                        goto fail;

                                goto got;

                        }

                        /* we lost it */

                        jbd2_journal_release_buffer(handle, bitmap_bh);

                        if (++ino < EXT4_INODES_PER_GROUP(sb))

                                goto repeat_in_this_group;

                }

                /*

                 * This case is possible in concurrent environment.  It is very

                 * rare.  We cannot repeat the find_group_xxx() call because

                 * that will simply return the same blockgroup, because the

                 * group descriptor metadata has not yet been updated.

                 * So we just go onto the next blockgroup.

                 */

                if (++group == sbi->s_groups_count)

                        group = 0;

        }

        err = -ENOSPC;

        goto out;

got:

        ino++;

        if ((group == 0 && ino < EXT4_FIRST_INO(sb)) ||

            ino > EXT4_INODES_PER_GROUP(sb)) {

                ext4_error(sb, __FUNCTION__,

                           "reserved inode or inode > inodes count - "

                           "block_group = %d, inode=%lu", group,

                           ino + group * EXT4_INODES_PER_GROUP(sb));

                err = -EIO;

                goto fail;

        }

        BUFFER_TRACE(bh2, "get_write_access");

        err = ext4_journal_get_write_access(handle, bh2);

        if (err) goto fail;

        /* We may have to initialize the block bitmap if it isn't already */

        if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM) &&

            gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {

                struct buffer_head *block_bh = read_block_bitmap(sb, group);

                BUFFER_TRACE(block_bh, "get block bitmap access");

                err = ext4_journal_get_write_access(handle, block_bh);

                if (err) {

                        brelse(block_bh);

                        goto fail;

                }

                free = 0;

                spin_lock(sb_bgl_lock(sbi, group));

                /* recheck and clear flag under lock if we still need to */

                if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {

                        gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);

                        free = ext4_free_blocks_after_init(sb, group, gdp);

                        gdp->bg_free_blocks_count = cpu_to_le16(free);

                }

                spin_unlock(sb_bgl_lock(sbi, group));

                /* Don't need to dirty bitmap block if we didn't change it */

                if (free) {

                        BUFFER_TRACE(block_bh, "dirty block bitmap");

                        err = ext4_journal_dirty_metadata(handle, block_bh);

                }

                brelse(block_bh);

                if (err)

                        goto fail;

        }

        spin_lock(sb_bgl_lock(sbi, group));

        /* If we didn't allocate from within the initialized part of the inode

         * table then we need to initialize up to this inode. */

        if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {

                if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {

                        gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT);

                        /* When marking the block group with

                         * ~EXT4_BG_INODE_UNINIT we don't want to depend

                         * on the value of bg_itable_unsed even though

                         * mke2fs could have initialized the same for us.

                         * Instead we calculated the value below

                         */

                        free = 0;

                } else {

                        free = EXT4_INODES_PER_GROUP(sb) -

                                le16_to_cpu(gdp->bg_itable_unused);

                }

                /*

                 * Check the relative inode number against the last used

                 * relative inode number in this group. if it is greater

                 * we need to  update the bg_itable_unused count

                 *

                 */

                if (ino > free)

                        gdp->bg_itable_unused =

                                cpu_to_le16(EXT4_INODES_PER_GROUP(sb) - ino);

        }

        gdp->bg_free_inodes_count =

                cpu_to_le16(le16_to_cpu(gdp->bg_free_inodes_count) - 1);

        if (S_ISDIR(mode)) {

                gdp->bg_used_dirs_count =

                        cpu_to_le16(le16_to_cpu(gdp->bg_used_dirs_count) + 1);

        }

        gdp->bg_checksum = ext4_group_desc_csum(sbi, group, gdp);

        spin_unlock(sb_bgl_lock(sbi, group));

        BUFFER_TRACE(bh2, "call ext4_journal_dirty_metadata");

        err = ext4_journal_dirty_metadata(handle, bh2);

        if (err) goto fail;

        percpu_counter_dec(&sbi->s_freeinodes_counter);

        if (S_ISDIR(mode))

                percpu_counter_inc(&sbi->s_dirs_counter);