fs/logfs/inode.c

   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  * wether 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  */
  49 static struct kmem_cache *logfs_inode_cache;
  50
  51 static DEFINE_SPINLOCK(logfs_inode_lock);
  52
  53 static 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 = &logfs_symlink_iops;
  68                 inode->i_mapping->a_ops = &logfs_reg_aops;
  69                 break;
  70         case S_IFSOCK:  /* fall through */
  71         case S_IFBLK:   /* fall through */
  72         case S_IFCHR:   /* fall through */
  73         case S_IFIFO:
  74                 init_special_inode(inode, inode->i_mode, inode->i_rdev);
  75                 break;
  76         default:
  77                 BUG();
  78         }
  79 }
  80
  81 static struct inode *__logfs_iget(struct super_block *sb, ino_t ino)
  82 {
  83         struct inode *inode = iget_locked(sb, ino);
  84         int err;
  85
  86         if (!inode)
  87                 return ERR_PTR(-ENOMEM);
  88         if (!(inode->i_state & I_NEW))
  89                 return inode;
  90
  91         err = logfs_read_inode(inode);
  92         if (err || inode->i_nlink == 0) {
  93                 /* inode->i_nlink == 0 can be true when called from
  94                  * block validator */
  95                 /* set i_nlink to 0 to prevent caching */
  96                 inode->i_nlink = 0;
  97                 logfs_inode(inode)->li_flags |= LOGFS_IF_ZOMBIE;
  98                 iget_failed(inode);
  99                 if (!err)
 100                         err = -ENOENT;
 101                 return ERR_PTR(err);
 102         }
 103
 104         logfs_inode_setops(inode);
 105         unlock_new_inode(inode);
 106         return inode;
 107 }
 108
 109 struct inode *logfs_iget(struct super_block *sb, ino_t ino)
 110 {
 111         BUG_ON(ino == LOGFS_INO_MASTER);
 112         BUG_ON(ino == LOGFS_INO_SEGFILE);
 113         return __logfs_iget(sb, ino);
 114 }
 115
 116 /*
 117  * is_cached is set to 1 if we hand out a cached inode, 0 otherwise.
 118  * this allows logfs_iput to do the right thing later
 119  */
 120 struct inode *logfs_safe_iget(struct super_block *sb, ino_t ino, int *is_cached)
 121 {
 122         struct logfs_super *super = logfs_super(sb);
 123         struct logfs_inode *li;
 124
 125         if (ino == LOGFS_INO_MASTER)
 126                 return super->s_master_inode;
 127         if (ino == LOGFS_INO_SEGFILE)
 128                 return super->s_segfile_inode;
 129
 130         spin_lock(&logfs_inode_lock);
 131         list_for_each_entry(li, &super->s_freeing_list, li_freeing_list)
 132                 if (li->vfs_inode.i_ino == ino) {
 133                         li->li_refcount++;
 134                         spin_unlock(&logfs_inode_lock);
 135                         *is_cached = 1;
 136                         return &li->vfs_inode;
 137                 }
 138         spin_unlock(&logfs_inode_lock);
 139
 140         *is_cached = 0;
 141         return __logfs_iget(sb, ino);
 142 }
 143
 144 static void __logfs_destroy_inode(struct inode *inode)
 145 {
 146         struct logfs_inode *li = logfs_inode(inode);
 147
 148         BUG_ON(li->li_block);
 149         list_del(&li->li_freeing_list);
 150         kmem_cache_free(logfs_inode_cache, li);
 151 }
 152
 153 static void logfs_destroy_inode(struct inode *inode)
 154 {
 155         struct logfs_inode *li = logfs_inode(inode);
 156
 157         BUG_ON(list_empty(&li->li_freeing_list));
 158         spin_lock(&logfs_inode_lock);
 159         li->li_refcount--;
 160         if (li->li_refcount == 0)
 161                 __logfs_destroy_inode(inode);
 162         spin_unlock(&logfs_inode_lock);
 163 }
 164
 165 void logfs_safe_iput(struct inode *inode, int is_cached)
 166 {
 167         if (inode->i_ino == LOGFS_INO_MASTER)
 168                 return;
 169         if (inode->i_ino == LOGFS_INO_SEGFILE)
 170                 return;
 171
 172         if (is_cached) {
 173                 logfs_destroy_inode(inode);
 174                 return;
 175         }
 176
 177         iput(inode);
 178 }
 179
 180 static void logfs_init_inode(struct super_block *sb, struct inode *inode)
 181 {
 182         struct logfs_inode *li = logfs_inode(inode);
 183         int i;
 184
 185         li->li_flags    = 0;
 186         li->li_height   = 0;
 187         li->li_used_bytes = 0;
 188         li->li_block    = NULL;
 189         inode->i_uid    = 0;
 190         inode->i_gid    = 0;
 191         inode->i_size   = 0;
 192         inode->i_blocks = 0;
 193         inode->i_ctime  = CURRENT_TIME;
 194         inode->i_mtime  = CURRENT_TIME;
 195         inode->i_nlink  = 1;
 196         li->li_refcount = 1;
 197         INIT_LIST_HEAD(&li->li_freeing_list);
 198
 199         for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
 200                 li->li_data[i] = 0;
 201
 202         return;
 203 }
 204
 205 static struct inode *logfs_alloc_inode(struct super_block *sb)
 206 {
 207         struct logfs_inode *li;
 208
 209         li = kmem_cache_alloc(logfs_inode_cache, GFP_NOFS);
 210         if (!li)
 211                 return NULL;
 212         logfs_init_inode(sb, &li->vfs_inode);
 213         return &li->vfs_inode;
 214 }
 215
 216 /*
 217  * In logfs inodes are written to an inode file.  The inode file, like any
 218  * other file, is managed with a inode.  The inode file's inode, aka master
 219  * inode, requires special handling in several respects.  First, it cannot be
 220  * written to the inode file, so it is stored in the journal instead.
 221  *
 222  * Secondly, this inode cannot be written back and destroyed before all other
 223  * inodes have been written.  The ordering is important.  Linux' VFS is happily
 224  * unaware of the ordering constraint and would ordinarily destroy the master
 225  * inode at umount time while other inodes are still in use and dirty.  Not
 226  * good.
 227  *
 228  * So logfs makes sure the master inode is not written until all other inodes
 229  * have been destroyed.  Sadly, this method has another side-effect.  The VFS
 230  * will notice one remaining inode and print a frightening warning message.
 231  * Worse, it is impossible to judge whether such a warning was caused by the
 232  * master inode or any other inodes have leaked as well.
 233  *
 234  * Our attempt of solving this is with logfs_new_meta_inode() below.  Its
 235  * purpose is to create a new inode that will not trigger the warning if such
 236  * an inode is still in use.  An ugly hack, no doubt.  Suggections for
 237  * improvement are welcome.
 238  *
 239  * AV: that's what ->put_super() is for...
 240  */
 241 struct inode *logfs_new_meta_inode(struct super_block *sb, u64 ino)
 242 {
 243         struct inode *inode;
 244
 245         inode = new_inode(sb);
 246         if (!inode)
 247                 return ERR_PTR(-ENOMEM);
 248
 249         inode->i_mode = S_IFREG;
 250         inode->i_ino = ino;
 251         inode->i_data.a_ops = &logfs_reg_aops;
 252         mapping_set_gfp_mask(&inode->i_data, GFP_NOFS);
 253
 254         return inode;
 255 }
 256
 257 struct inode *logfs_read_meta_inode(struct super_block *sb, u64 ino)
 258 {
 259         struct inode *inode;
 260         int err;
 261
 262         inode = logfs_new_meta_inode(sb, ino);
 263         if (IS_ERR(inode))
 264                 return inode;
 265
 266         err = logfs_read_inode(inode);
 267         if (err) {
 268                 iput(inode);
 269                 return ERR_PTR(err);
 270         }
 271         logfs_inode_setops(inode);
 272         return inode;
 273 }
 274
 275 static int logfs_write_inode(struct inode *inode, struct writeback_control *wbc)
 276 {
 277         int ret;
 278         long flags = WF_LOCK;
 279
 280         /* Can only happen if creat() failed.  Safe to skip. */
 281         if (logfs_inode(inode)->li_flags & LOGFS_IF_STILLBORN)
 282                 return 0;
 283
 284         ret = __logfs_write_inode(inode, flags);
 285         LOGFS_BUG_ON(ret, inode->i_sb);
 286         return ret;
 287 }
 288
 289 /* called with inode_lock held */
 290 static int logfs_drop_inode(struct inode *inode)
 291 {
 292         struct logfs_super *super = logfs_super(inode->i_sb);
 293         struct logfs_inode *li = logfs_inode(inode);
 294
 295         spin_lock(&logfs_inode_lock);
 296         list_move(&li->li_freeing_list, &super->s_freeing_list);
 297         spin_unlock(&logfs_inode_lock);
 298         return generic_drop_inode(inode);
 299 }
 300
 301 static void logfs_set_ino_generation(struct super_block *sb,
 302                 struct inode *inode)
 303 {
 304         struct logfs_super *super = logfs_super(sb);
 305         u64 ino;
 306
 307         mutex_lock(&super->s_journal_mutex);
 308         ino = logfs_seek_hole(super->s_master_inode, super->s_last_ino + 1);
 309         super->s_last_ino = ino;
 310         super->s_inos_till_wrap--;
 311         if (super->s_inos_till_wrap < 0) {
 312                 super->s_last_ino = LOGFS_RESERVED_INOS;
 313                 super->s_generation++;
 314                 super->s_inos_till_wrap = INOS_PER_WRAP;
 315         }
 316         inode->i_ino = ino;
 317         inode->i_generation = super->s_generation;
 318         mutex_unlock(&super->s_journal_mutex);
 319 }
 320
 321 struct inode *logfs_new_inode(struct inode *dir, int mode)
 322 {
 323         struct super_block *sb = dir->i_sb;
 324         struct inode *inode;
 325
 326         inode = new_inode(sb);
 327         if (!inode)
 328                 return ERR_PTR(-ENOMEM);
 329
 330         logfs_init_inode(sb, inode);
 331
 332         /* inherit parent flags */
 333         logfs_inode(inode)->li_flags |=
 334                 logfs_inode(dir)->li_flags & LOGFS_FL_INHERITED;
 335
 336         inode->i_mode = mode;
 337         logfs_set_ino_generation(sb, inode);
 338
 339         inode_init_owner(inode, dir, mode);
 340         logfs_inode_setops(inode);
 341         insert_inode_hash(inode);
 342
 343         return inode;
 344 }
 345
 346 static void logfs_init_once(void *_li)
 347 {
 348         struct logfs_inode *li = _li;
 349         int i;
 350
 351         li->li_flags = 0;
 352         li->li_used_bytes = 0;
 353         li->li_refcount = 1;
 354         for (i = 0; i < LOGFS_EMBEDDED_FIELDS; i++)
 355                 li->li_data[i] = 0;
 356         inode_init_once(&li->vfs_inode);
 357 }
 358
 359 static int logfs_sync_fs(struct super_block *sb, int wait)
 360 {
 361         logfs_write_anchor(sb);
 362         return 0;
 363 }
 364
 365 static void logfs_put_super(struct super_block *sb)
 366 {
 367         struct logfs_super *super = logfs_super(sb);
 368         /* kill the meta-inodes */
 369         iput(super->s_master_inode);
 370         iput(super->s_segfile_inode);
 371         iput(super->s_mapping_inode);
 372 }
 373
 374 const struct super_operations logfs_super_operations = {
 375         .alloc_inode    = logfs_alloc_inode,
 376         .destroy_inode  = logfs_destroy_inode,
 377         .evict_inode    = logfs_evict_inode,
 378         .drop_inode     = logfs_drop_inode,
 379         .put_super      = logfs_put_super,
 380         .write_inode    = logfs_write_inode,
 381         .statfs         = logfs_statfs,
 382         .sync_fs        = logfs_sync_fs,
 383 };
 384
 385 int logfs_init_inode_cache(void)
 386 {
 387         logfs_inode_cache = kmem_cache_create("logfs_inode_cache",
 388                         sizeof(struct logfs_inode), 0, SLAB_RECLAIM_ACCOUNT,
 389                         logfs_init_once);
 390         if (!logfs_inode_cache)
 391                 return -ENOMEM;
 392         return 0;
 393 }
 394
 395 void logfs_destroy_inode_cache(void)
 396 {
 397         kmem_cache_destroy(logfs_inode_cache);
 398 }