linux/fs/logfs/inode.c
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   1/*
   2 * fs/logfs/inode.c     - inode handling code
   3 *
   4 * As should be obvious for Linux kernel code, license is GPLv2
   5 *
   6 * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
   7 */
   8#include "logfs.h"
   9#include <linux/slab.h>
  10#include <linux/writeback.h>
  11#include <linux/backing-dev.h>
  12
  13/*
  14 * How soon to reuse old inode numbers?  LogFS doesn't store deleted inodes
  15 * on the medium.  It therefore also lacks a method to store the previous
  16 * generation number for deleted inodes.  Instead a single generation number
  17 * is stored which will be used for new inodes.  Being just a 32bit counter,
  18 * this can obvious wrap relatively quickly.  So we only reuse inodes if we
  19 * know that a fair number of inodes can be created before we have to increment
  20 * the generation again - effectively adding some bits to the counter.
  21 * But being too aggressive here means we keep a very large and very sparse
  22 * inode file, wasting space on indirect blocks.
  23 * So what is a good value?  Beats me.  64k seems moderately bad on both
  24 * fronts, so let's use that for now...
  25 *
  26 * NFS sucks, as everyone already knows.
  27 */
  28#define INOS_PER_WRAP (0x10000)
  29
  30/*
  31 * Logfs' requirement to read inodes for garbage collection makes life a bit
  32 * harder.  GC may have to read inodes that are in I_FREEING state, when they
  33 * are being written out - and waiting for GC to make progress, naturally.
  34 *
  35 * So we cannot just call iget() or some variant of it, but first have to check
  36 * whether the inode in question might be in I_FREEING state.  Therefore we
  37 * maintain our own per-sb list of "almost deleted" inodes and check against
  38 * that list first.  Normally this should be at most 1-2 entries long.
  39 *
  40 * Also, inodes have logfs-specific reference counting on top of what the vfs
  41 * does.  When .destroy_inode is called, normally the reference count will drop
  42 * to zero and the inode gets deleted.  But if GC accessed the inode, its
  43 * refcount will remain nonzero and final deletion will have to wait.
  44 *
  45 * As a result we have two sets of functions to get/put inodes:
  46 * logfs_safe_iget/logfs_safe_iput      - safe to call from GC context
  47 * logfs_iget/iput                      - normal version
  48 */
  49static struct kmem_cache *logfs_inode_cache;
  50
  51static DEFINE_SPINLOCK(logfs_inode_lock);
  52
  53static void logfs_inode_setops(struct inode *inode)
  54{
  55        switch (inode->i_mode & S_IFMT) {
  56        case S_IFDIR:
  57                inode->i_op = &logfs_dir_iops;
  58                inode->i_fop = &logfs_dir_fops;
  59                inode->i_mapping->a_ops = &logfs_reg_aops;
  60                break;
  61        case S_IFREG:
  62                inode->i_op = &logfs_reg_iops;
  63                inode->i_fop = &logfs_reg_fops;
  64                inode->i_mapping->a_ops = &logfs_reg_aops;
  65                break;
  66        case S_IFLNK:
  67                inode->i_op = &page_symlink_inode_operations;
  68                inode_nohighmem(inode);
  69                inode->i_mapping->a_ops = &logfs_reg_aops;
  70                break;
  71        case S_IFSOCK:  /* fall through */
  72        case S_IFBLK:   /* fall through */
  73        case S_IFCHR:   /* fall through */
  74        case S_IFIFO:
  75                init_special_inode(inode, inode->i_mode, inode->i_rdev);
  76                break;
  77        default:
  78                BUG();
  79        }
  80}
  81
  82static struct inode *__logfs_iget(struct super_block *sb, ino_t ino)
  83{
  84        struct inode *inode = iget_locked(sb, ino);
  85        int err;
  86
  87        if (!inode)
  88                return ERR_PTR(-ENOMEM);
  89        if (!(inode->i_state & I_NEW))
  90                return inode;
  91
  92        err = logfs_read_inode(inode);
  93        if (err || inode->i_nlink == 0) {
  94                /* inode->i_nlink == 0 can be true when called from
  95                 * block validator */
  96                /* set i_nlink to 0 to prevent caching */
  97                clear_nlink(inode);
  98                logfs_inode(inode)->li_flags |= LOGFS_IF_ZOMBIE;
  99                iget_failed(inode);
 100                if (!err)
 101                        err = -ENOENT;
 102                return ERR_PTR(err);
 103        }
 104
 105        logfs_inode_setops(inode);
 106        unlock_new_inode(inode);
 107        return inode;
 108}
 109
 110struct inode *logfs_iget(struct super_block *sb, ino_t ino)
 111{
 112        BUG_ON(ino == LOGFS_INO_MASTER);
 113        BUG_ON(ino == LOGFS_INO_SEGFILE);
 114        return __logfs_iget(sb, ino);
 115}
 116
 117/*
 118 * is_cached is set to 1 if we hand out a cached inode, 0 otherwise.
 119 * this allows logfs_iput to do the right thing later
 120 */
 121struct inode *logfs_safe_iget(struct super_block *sb, ino_t ino, int *is_cached)
 122{
 123        struct logfs_super *super = logfs_super(sb);
 124        struct logfs_inode *li;
 125
 126        if (ino == LOGFS_INO_MASTER)
 127                return super->s_master_inode;
 128        if (ino == LOGFS_INO_SEGFILE)
 129                return super->s_segfile_inode;
 130
 131        spin_lock(&logfs_inode_lock);
 132        list_for_each_entry(li, &super->s_freeing_list, li_freeing_list)
 133                if (li->vfs_inode.i_ino == ino) {
 134                        li->li_refcount++;
 135                        spin_unlock(&logfs_inode_lock);
 136                        *is_cached = 1;
 137                        return &li->vfs_inode;
 138                }
 139        spin_unlock(&logfs_inode_lock);
 140
 141        *is_cached = 0;
 142        return __logfs_iget(sb, ino);
 143}
 144
 145static void logfs_i_callback(struct rcu_head *head)
 146{
 147        struct inode *inode = container_of(head, struct inode, i_rcu);
 148        kmem_cache_free(logfs_inode_cache, logfs_inode(inode));
 149}
 150
 151static void __logfs_destroy_inode(struct inode *inode)
 152{
 153        struct logfs_inode *li = logfs_inode(inode);
 154
 155        BUG_ON(li->li_block);
 156        list_del(&li->li_freeing_list);
 157        call_rcu(&inode->i_rcu, logfs_i_callback);
 158}
 159
 160static void __logfs_destroy_meta_inode(struct inode *inode)
 161{
 162        struct logfs_inode *li = logfs_inode(inode);
 163        BUG_ON(li->li_block);
 164        call_rcu(&inode->i_rcu, logfs_i_callback);
 165}
 166
 167static void logfs_destroy_inode(struct inode *inode)
 168{
 169        struct logfs_inode *li = logfs_inode(inode);
 170
 171        if (inode->i_ino < LOGFS_RESERVED_INOS) {
 172                /*
 173                 * The reserved inodes are never destroyed unless we are in
 174                 * unmont path.
 175                 */
 176                __logfs_destroy_meta_inode(inode);
 177                return;
 178        }
 179
 180        BUG_ON(list_empty(&li->li_freeing_list));
 181        spin_lock(&logfs_inode_lock);
 182        li->li_refcount--;
 183        if (li->li_refcount == 0)
 184                __logfs_destroy_inode(inode);
 185        spin_unlock(&logfs_inode_lock);
 186}
 187
 188void logfs_safe_iput(struct inode *inode, int is_cached)
 189{
 190        if (inode->i_ino == LOGFS_INO_MASTER)
 191                return;
 192        if (inode->i_ino == LOGFS_INO_SEGFILE)
 193                return;
 194
 195        if (is_cached) {
 196                logfs_destroy_inode(inode);
 197                return;
 198        }
 199
 200        iput(inode);
 201}
 202
 203static void logfs_init_inode(struct super_block *sb, struct inode *inode)
 204{
 205        struct logfs_inode *li = logfs_inode(inode);
 206        int i;
 207
 208        li->li_flags    = 0;
 209        li->li_height   = 0;
 210        li->li_used_bytes = 0;
 211        li->li_block    = NULL;
 212        i_uid_write(inode, 0);
 213        i_gid_write(inode, 0);
 214        inode->i_size   = 0;
 215        inode->i_blocks = 0;
 216        inode->i_ctime  = current_time(inode);
 217        inode->i_mtime  = current_time(inode);
 218        li->li_refcount = 1;
 219        INIT_LIST_HEAD(&li->li_freeing_list);
 220
 221        for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
 222                li->li_data[i] = 0;
 223
 224        return;
 225}
 226
 227static struct inode *logfs_alloc_inode(struct super_block *sb)
 228{
 229        struct logfs_inode *li;
 230
 231        li = kmem_cache_alloc(logfs_inode_cache, GFP_NOFS);
 232        if (!li)
 233                return NULL;
 234        logfs_init_inode(sb, &li->vfs_inode);
 235        return &li->vfs_inode;
 236}
 237
 238/*
 239 * In logfs inodes are written to an inode file.  The inode file, like any
 240 * other file, is managed with a inode.  The inode file's inode, aka master
 241 * inode, requires special handling in several respects.  First, it cannot be
 242 * written to the inode file, so it is stored in the journal instead.
 243 *
 244 * Secondly, this inode cannot be written back and destroyed before all other
 245 * inodes have been written.  The ordering is important.  Linux' VFS is happily
 246 * unaware of the ordering constraint and would ordinarily destroy the master
 247 * inode at umount time while other inodes are still in use and dirty.  Not
 248 * good.
 249 *
 250 * So logfs makes sure the master inode is not written until all other inodes
 251 * have been destroyed.  Sadly, this method has another side-effect.  The VFS
 252 * will notice one remaining inode and print a frightening warning message.
 253 * Worse, it is impossible to judge whether such a warning was caused by the
 254 * master inode or any other inodes have leaked as well.
 255 *
 256 * Our attempt of solving this is with logfs_new_meta_inode() below.  Its
 257 * purpose is to create a new inode that will not trigger the warning if such
 258 * an inode is still in use.  An ugly hack, no doubt.  Suggections for
 259 * improvement are welcome.
 260 *
 261 * AV: that's what ->put_super() is for...
 262 */
 263struct inode *logfs_new_meta_inode(struct super_block *sb, u64 ino)
 264{
 265        struct inode *inode;
 266
 267        inode = new_inode(sb);
 268        if (!inode)
 269                return ERR_PTR(-ENOMEM);
 270
 271        inode->i_mode = S_IFREG;
 272        inode->i_ino = ino;
 273        inode->i_data.a_ops = &logfs_reg_aops;
 274        mapping_set_gfp_mask(&inode->i_data, GFP_NOFS);
 275
 276        return inode;
 277}
 278
 279struct inode *logfs_read_meta_inode(struct super_block *sb, u64 ino)
 280{
 281        struct inode *inode;
 282        int err;
 283
 284        inode = logfs_new_meta_inode(sb, ino);
 285        if (IS_ERR(inode))
 286                return inode;
 287
 288        err = logfs_read_inode(inode);
 289        if (err) {
 290                iput(inode);
 291                return ERR_PTR(err);
 292        }
 293        logfs_inode_setops(inode);
 294        return inode;
 295}
 296
 297static int logfs_write_inode(struct inode *inode, struct writeback_control *wbc)
 298{
 299        int ret;
 300        long flags = WF_LOCK;
 301
 302        /* Can only happen if creat() failed.  Safe to skip. */
 303        if (logfs_inode(inode)->li_flags & LOGFS_IF_STILLBORN)
 304                return 0;
 305
 306        ret = __logfs_write_inode(inode, NULL, flags);
 307        LOGFS_BUG_ON(ret, inode->i_sb);
 308        return ret;
 309}
 310
 311/* called with inode->i_lock held */
 312static int logfs_drop_inode(struct inode *inode)
 313{
 314        struct logfs_super *super = logfs_super(inode->i_sb);
 315        struct logfs_inode *li = logfs_inode(inode);
 316
 317        spin_lock(&logfs_inode_lock);
 318        list_move(&li->li_freeing_list, &super->s_freeing_list);
 319        spin_unlock(&logfs_inode_lock);
 320        return generic_drop_inode(inode);
 321}
 322
 323static void logfs_set_ino_generation(struct super_block *sb,
 324                struct inode *inode)
 325{
 326        struct logfs_super *super = logfs_super(sb);
 327        u64 ino;
 328
 329        mutex_lock(&super->s_journal_mutex);
 330        ino = logfs_seek_hole(super->s_master_inode, super->s_last_ino + 1);
 331        super->s_last_ino = ino;
 332        super->s_inos_till_wrap--;
 333        if (super->s_inos_till_wrap < 0) {
 334                super->s_last_ino = LOGFS_RESERVED_INOS;
 335                super->s_generation++;
 336                super->s_inos_till_wrap = INOS_PER_WRAP;
 337        }
 338        inode->i_ino = ino;
 339        inode->i_generation = super->s_generation;
 340        mutex_unlock(&super->s_journal_mutex);
 341}
 342
 343struct inode *logfs_new_inode(struct inode *dir, umode_t mode)
 344{
 345        struct super_block *sb = dir->i_sb;
 346        struct inode *inode;
 347
 348        inode = new_inode(sb);
 349        if (!inode)
 350                return ERR_PTR(-ENOMEM);
 351
 352        logfs_init_inode(sb, inode);
 353
 354        /* inherit parent flags */
 355        logfs_inode(inode)->li_flags |=
 356                logfs_inode(dir)->li_flags & LOGFS_FL_INHERITED;
 357
 358        inode->i_mode = mode;
 359        logfs_set_ino_generation(sb, inode);
 360
 361        inode_init_owner(inode, dir, mode);
 362        logfs_inode_setops(inode);
 363        insert_inode_hash(inode);
 364
 365        return inode;
 366}
 367
 368static void logfs_init_once(void *_li)
 369{
 370        struct logfs_inode *li = _li;
 371        int i;
 372
 373        li->li_flags = 0;
 374        li->li_used_bytes = 0;
 375        li->li_refcount = 1;
 376        for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
 377                li->li_data[i] = 0;
 378        inode_init_once(&li->vfs_inode);
 379}
 380
 381static int logfs_sync_fs(struct super_block *sb, int wait)
 382{
 383        logfs_get_wblocks(sb, NULL, WF_LOCK);
 384        logfs_write_anchor(sb);
 385        logfs_put_wblocks(sb, NULL, WF_LOCK);
 386        return 0;
 387}
 388
 389static void logfs_put_super(struct super_block *sb)
 390{
 391        struct logfs_super *super = logfs_super(sb);
 392        /* kill the meta-inodes */
 393        iput(super->s_segfile_inode);
 394        iput(super->s_master_inode);
 395        iput(super->s_mapping_inode);
 396}
 397
 398const struct super_operations logfs_super_operations = {
 399        .alloc_inode    = logfs_alloc_inode,
 400        .destroy_inode  = logfs_destroy_inode,
 401        .evict_inode    = logfs_evict_inode,
 402        .drop_inode     = logfs_drop_inode,
 403        .put_super      = logfs_put_super,
 404        .write_inode    = logfs_write_inode,
 405        .statfs         = logfs_statfs,
 406        .sync_fs        = logfs_sync_fs,
 407};
 408
 409int logfs_init_inode_cache(void)
 410{
 411        logfs_inode_cache = kmem_cache_create("logfs_inode_cache",
 412                        sizeof(struct logfs_inode), 0,
 413                        SLAB_RECLAIM_ACCOUNT|SLAB_ACCOUNT,
 414                        logfs_init_once);
 415        if (!logfs_inode_cache)
 416                return -ENOMEM;
 417        return 0;
 418}
 419
 420void logfs_destroy_inode_cache(void)
 421{
 422        /*
 423         * Make sure all delayed rcu free inodes are flushed before we
 424         * destroy cache.
 425         */
 426        rcu_barrier();
 427        kmem_cache_destroy(logfs_inode_cache);
 428}
 429