Large store support for ext2fs

This is a revised version of the large store patch for ext2fs, written
by Ognyan Kulev. It provides support for stores larger than 2 GiB.

* ext2fs/balloc.c: Use the new disk_cache_block_ref and disk_cache_block_deref
functions to access blocks from the disk cache.
* ext2fs/ext2fs.c (main): Update initialization call to pokel_init, and
call map_hypermetadata instead of get_hypermetadata.
* ext2fs/ext2fs.h: Include <hurd/store.h> and <hurd/ihash.h>.
(DISK_CACHE_BLOCKS): New macro.
(DC_INCORE): Likewise.
(DC_UNTOUCHED): Likewise.
(DC_FIXED): Likewise.
(DC_DONT_REUSE): Likewise.
(DC_NO_BLOCK): Likewise.
(DISK_CACHE_LAST_READ_XOR) [!NDEBUG]: Likewise.
(struct disk_cache_info): New structure.
(disk_cache): New external variable.
(disk_cache_size): Likewise.
(disk_cache_blocks): Likewise.
(disk_cache_bptr): Likewise.
(disk_cache_info): Likewise.
(disk_cache_lock): Likewise.
(disk_cache_reassociation): Likewise.
(disk_cache_block_ref): New declaration.
(disk_cache_block_ref_ptr): Likewise.
(disk_cache_block_deref): Likewise.
(disk_cache_block_is_ref): Likewise.
(map_hypermetadata): Likewise.
(trunc_block): Cast to off_t.
(round_block): Likewise.
(boffs): Likewise.
(bptr_index): New macro.
(boffs_ptr): Rewrite as an inline function to make it look up a block from
the disk cache.
(bptr_offs): Likewise.
(dino): Remove function, replaced with ...
(dino_ref): ... this one, which adds a reference to the inode block.
(dino_deref): New inline function.
(record_global_poke): Make sure block is referenced.
(record_indir_poke): Likewise.
(sync_global_ptr): Remove block reference, and adjust call to
pager_sync_some.
(sync_global): Add debug call to print wait parameter.
* ext2fs/getblk.c: Use the new disk_cache_block_ref and disk_cache_block_deref
functions to access blocks from the disk cache.
* ext2fs/hyper.c (get_hypermetadata): Read the superblock from the store
now that it's not directly mapped in memory. Move the initialization of
zeroblock here from ...
(map_hypermetadata): ... here. Also, set the superblock pointer.
(diskfs_set_hypermetadata): Add a reference to the superblock.
(diskfs_readonly_changed): Update call to mprotect.
* ext2fs/ialloc.c: Use the new disk_cache_block_ref, disk_cache_block_ref_ptr
and disk_cache_block_deref functions to access blocks from the disk cache.
* ext2fs/inode.c: Update calls that used the disk image to use the disk cache,
and use the new reference handling functions where appropriate.
* ext2fs/pager.c: Include <unistd.h> and "../libpager/priv.h".
(disk_image): Remove global variable.
(disk_pager_read_page): Update cache information.
(disk_pager_write_page): Likewise.
(disk_pager_notify_evict): New function.
(pager_notify_evict): Call disk_pager_notify_evict appropriately.
(disk_cache): New global variable.
(disk_cache_size): Likewise.
(disk_cache_blocks): Likewise.
(disk_cache_bptr): Likewise.
(disk_cache_info): Likewise.
(disk_cache_hint): Likewise.
(disk_cache_lock): Likewise.
(disk_cache_reassociation): Likewise.
(disk_cache_init): New function.
(disk_cache_return_unused): Likewise.
(disk_cache_block_ref): Likewise.
(disk_cache_block_ref_ptr): Likewise.
(disk_cache_block_deref): Likewise.
(disk_cache_block_is_ref): Likewise.
(create_disk_pager): Update initialization of the disk pager.
* ext2fs/pokel.c (pokel_add): Drop block references with disk_cache_block_deref.
(_pokel_exec): Likewise.
* ext2fs/truncate.c (trunc_indirect): Use the new disk_cache_block_ref and
disk_cache_block_deref functions to access blocks from the disk cache.

10 files changed, 733 insertions, 91 deletions

diff --git a/ext2fs/balloc.c b/ext2fs/balloc.c
index b2d2eab9..efef8ae4 100644
--- a/ext2fs/balloc.c
+++ b/ext2fs/balloc.c
@@ -92,7 +92,7 @@ ext2_free_blocks (block_t block, unsigned long count)
 		      block, count);
 	}
       gdp = group_desc (block_group);
-      bh = bptr (gdp->bg_block_bitmap);
+      bh = disk_cache_block_ref (gdp->bg_block_bitmap);
 
       if (in_range (gdp->bg_block_bitmap, block, gcount) ||
 	  in_range (gdp->bg_inode_bitmap, block, gcount) ||
@@ -114,6 +114,7 @@ ext2_free_blocks (block_t block, unsigned long count)
 	}
 
       record_global_poke (bh);
+      disk_cache_block_ref_ptr (gdp);
       record_global_poke (gdp);
 
       block += gcount;
@@ -139,7 +140,7 @@ ext2_new_block (block_t goal,
 		block_t prealloc_goal,
 		block_t *prealloc_count, block_t *prealloc_block)
 {
-  char *bh;
+  char *bh = NULL;
   char *p, *r;
   int i, j, k, tmp;
   unsigned long lmap;
@@ -165,6 +166,7 @@ ext2_new_block (block_t goal,
   ext2_debug ("goal=%u", goal);
 
 repeat:
+  assert (bh == NULL);
   /*
      * First, test whether the goal block is free.
    */
@@ -179,7 +181,7 @@ repeat:
       if (j)
 	goal_attempts++;
 #endif
-      bh = bptr (gdp->bg_block_bitmap);
+      bh = disk_cache_block_ref (gdp->bg_block_bitmap);
 
       ext2_debug ("goal is at %d:%d", i, j);
 
@@ -245,6 +247,9 @@ repeat:
 	  j = k;
 	  goto got_block;
 	}
+
+      disk_cache_block_deref (bh);
+      bh = NULL;
     }
 
   ext2_debug ("bit not found in block group %d", i);
@@ -267,7 +272,8 @@ repeat:
       pthread_spin_unlock (&global_lock);
       return 0;
     }
-  bh = bptr (gdp->bg_block_bitmap);
+  assert (bh == NULL);
+  bh = disk_cache_block_ref (gdp->bg_block_bitmap);
   r = memscan (bh, 0, sblock->s_blocks_per_group >> 3);
   j = (r - bh) << 3;
   if (j < sblock->s_blocks_per_group)
@@ -277,12 +283,15 @@ repeat:
 			     sblock->s_blocks_per_group);
   if (j >= sblock->s_blocks_per_group)
     {
+      disk_cache_block_deref (bh);
+      bh = NULL;
       ext2_error ("free blocks count corrupted for block group %d", i);
       pthread_spin_unlock (&global_lock);
       return 0;
     }
 
 search_back:
+  assert (bh != NULL);
   /*
      * We have succeeded in finding a free byte in the block
      * bitmap.  Now search backwards up to 7 bits to find the
@@ -291,6 +300,7 @@ search_back:
   for (k = 0; k < 7 && j > 0 && !test_bit (j - 1, bh); k++, j--);
 
 got_block:
+  assert (bh != NULL);
 
   ext2_debug ("using block group %d (%d)", i, gdp->bg_free_blocks_count);
 
@@ -304,6 +314,8 @@ got_block:
   if (set_bit (j, bh))
     {
       ext2_warning ("bit already set for block %d", j);
+      disk_cache_block_deref (bh);
+      bh = NULL;
       goto repeat;
     }
 
@@ -351,6 +363,7 @@ got_block:
   j = tmp;
 
   record_global_poke (bh);
+  bh = NULL;
 
   if (j >= sblock->s_blocks_count)
     {
@@ -363,12 +376,14 @@ got_block:
 	      j, goal_hits, goal_attempts);
 
   gdp->bg_free_blocks_count--;
+  disk_cache_block_ref_ptr (gdp);
   record_global_poke (gdp);
 
   sblock->s_free_blocks_count--;
   sblock_dirty = 1;
 
  sync_out:
+  assert (bh == NULL);
   pthread_spin_unlock (&global_lock);
   alloc_sync (0);
 
@@ -390,9 +405,12 @@ ext2_count_free_blocks ()
   gdp = NULL;
   for (i = 0; i < groups_count; i++)
     {
+      void *bh;
       gdp = group_desc (i);
       desc_count += gdp->bg_free_blocks_count;
-      x = count_free (bptr (gdp->bg_block_bitmap), block_size);
+      bh = disk_cache_block_ref (gdp->bg_block_bitmap);
+      x = count_free (bh, block_size);
+      disk_cache_block_deref (bh);
       printf ("group %d: stored = %d, counted = %lu",
 	      i, gdp->bg_free_blocks_count, x);
       bitmap_count += x;
@@ -453,7 +471,7 @@ ext2_check_blocks_bitmap ()
 
       gdp = group_desc (i);
       desc_count += gdp->bg_free_blocks_count;
-      bh = bptr (gdp->bg_block_bitmap);
+      bh = disk_cache_block_ref (gdp->bg_block_bitmap);
 
       if (!EXT2_HAS_RO_COMPAT_FEATURE (sblock,
 				       EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)
@@ -479,6 +497,7 @@ ext2_check_blocks_bitmap ()
 	  ext2_error ("block #%d of the inode table in group %d is marked free", j, i);
 
       x = count_free (bh, block_size);
+      disk_cache_block_deref (bh);
       if (gdp->bg_free_blocks_count != x)
 	ext2_error ("wrong free blocks count for group %d,"
 		    " stored = %d, counted = %lu",
diff --git a/ext2fs/ext2fs.c b/ext2fs/ext2fs.c
index 993f1997..128b6edd 100644
--- a/ext2fs/ext2fs.c
+++ b/ext2fs/ext2fs.c
@@ -181,9 +181,9 @@ main (int argc, char **argv)
   /* Map the entire disk. */
   create_disk_pager ();
 
-  pokel_init (&global_pokel, diskfs_disk_pager, disk_image);
+  pokel_init (&global_pokel, diskfs_disk_pager, disk_cache);
 
-  get_hypermetadata();
+  map_hypermetadata ();
 
   inode_init ();
 
@@ -211,6 +211,8 @@ diskfs_reload_global_state ()
 {
   pokel_flush (&global_pokel);
   pager_flush (diskfs_disk_pager, 1);
+  sblock = NULL;
   get_hypermetadata ();
+  map_hypermetadata ();
   return 0;
 }
diff --git a/ext2fs/ext2fs.h b/ext2fs/ext2fs.h
index 52bf2b19..e01d1a59 100644
--- a/ext2fs/ext2fs.h
+++ b/ext2fs/ext2fs.h
@@ -23,7 +23,9 @@
 #include <hurd/pager.h>
 #include <hurd/fshelp.h>
 #include <hurd/iohelp.h>
+#include <hurd/store.h>
 #include <hurd/diskfs.h>
+#include <hurd/ihash.h>
 #include <assert.h>
 #include <pthread.h>
 #include <sys/mman.h>
@@ -195,6 +197,8 @@ struct user_pager_info
 /* ---------------------------------------------------------------- */
 /* pager.c */
 
+#define DISK_CACHE_BLOCKS	65536
+
 #include <hurd/diskfs-pager.h>
 
 /* Set up the disk pager.  */
@@ -218,10 +222,54 @@ extern struct store *store;
 /* What the user specified.  */
 extern struct store_parsed *store_parsed;
 
-/* Mapped image of the disk.  */
-extern void *disk_image;
+/* Mapped image of cached blocks of the disk.  */
+extern void *disk_cache;
+extern store_offset_t disk_cache_size;
+extern int disk_cache_blocks;
+
+#define DC_INCORE	0x01	/* Not in core.  */
+#define DC_UNTOUCHED	0x02	/* Not touched by disk_pager_read_paged
+				   or disk_cache_block_ref.  */
+#define DC_FIXED	0x04	/* Must not be re-associated.  */
+
+/* Flags that forbid re-association of page.  DC_UNTOUCHED is included
+   because this flag is used only when page is already to be
+   re-associated, so it's not good candidate for another
+   remapping.  */
+#define DC_DONT_REUSE	(DC_INCORE | DC_UNTOUCHED | DC_FIXED)
+
+#define DC_NO_BLOCK	((block_t) -1L)
+
+#ifndef NDEBUG
+#define DISK_CACHE_LAST_READ_XOR	0xDEADBEEF
+#endif
+
+/* Disk cache blocks' meta info.  */
+struct disk_cache_info
+{
+  block_t block;
+  uint16_t flags;
+  uint16_t ref_count;
+#ifndef NDEBUG
+  block_t last_read, last_read_xor;
+#endif
+};
 
-/* Our in-core copy of the super-block (pointer into the disk_image).  */
+/* block num --> pointer to in-memory block */
+extern hurd_ihash_t disk_cache_bptr;
+/* Metadata about cached block. */
+extern struct disk_cache_info *disk_cache_info;
+/* Lock for these mappings */
+extern pthread_mutex_t disk_cache_lock;
+/* Fired when a re-association is done.  */
+extern pthread_cond_t disk_cache_reassociation;
+
+void *disk_cache_block_ref (block_t block);
+void disk_cache_block_ref_ptr (void *ptr);
+void disk_cache_block_deref (void *ptr);
+int disk_cache_block_is_ref (block_t block);
+
+/* Our in-core copy of the super-block (pointer into the disk_cache).  */
 struct ext2_super_block *sblock;
 /* True if sblock has been modified.  */
 int sblock_dirty;
@@ -251,6 +299,9 @@ vm_address_t zeroblock;
 
 /* Get the superblock from the disk, & setup various global info from it.  */
 void get_hypermetadata ();
+
+/* Map `sblock' and `group_desc_image' pointers to disk cache.  */
+void map_hypermetadata ();
 
 /* ---------------------------------------------------------------- */
 /* Random stuff calculated from the super block.  */
@@ -274,21 +325,51 @@ pthread_spinlock_t generation_lock;
 unsigned long next_generation;
 
 /* ---------------------------------------------------------------- */
-/* Functions for looking inside disk_image */
+/* Functions for looking inside disk_cache */
 
-#define trunc_block(offs) (((offs) >> log2_block_size) << log2_block_size)
+#define trunc_block(offs) \
+  ((off_t) ((offs) >> log2_block_size) << log2_block_size)
 #define round_block(offs) \
-  ((((offs) + block_size - 1) >> log2_block_size) << log2_block_size)
+  ((off_t) (((offs) + block_size - 1) >> log2_block_size) << log2_block_size)
 
 /* block num --> byte offset on disk */
-#define boffs(block) ((block) << log2_block_size)
+#define boffs(block) ((off_t) (block) << log2_block_size)
 /* byte offset on disk --> block num */
 #define boffs_block(offs) ((offs) >> log2_block_size)
 
+/* pointer to in-memory block -> index in disk_cache_info */
+#define bptr_index(ptr) (((char *)ptr - (char *)disk_cache) >> log2_block_size)
+
 /* byte offset on disk --> pointer to in-memory block */
-#define boffs_ptr(offs) (((char *)disk_image) + (offs))
+EXT2FS_EI char *
+boffs_ptr (off_t offset)
+{
+  block_t block = boffs_block (offset);
+  pthread_mutex_lock (&disk_cache_lock);
+  char *ptr = hurd_ihash_find (disk_cache_bptr, block);
+  pthread_mutex_unlock (&disk_cache_lock);
+  assert (ptr);
+  ptr += offset % block_size;
+  ext2_debug ("(%lld) = %p", offset, ptr);
+  return ptr;
+}
+
 /* pointer to in-memory block --> byte offset on disk */
-#define bptr_offs(ptr) ((char *)(ptr) - ((char *)disk_image))
+EXT2FS_EI off_t
+bptr_offs (void *ptr)
+{
+  vm_offset_t mem_offset = (char *)ptr - (char *)disk_cache;
+  off_t offset;
+  assert (mem_offset < disk_cache_size);
+  pthread_mutex_lock (&disk_cache_lock);
+  offset = (off_t) disk_cache_info[boffs_block (mem_offset)].block
+    << log2_block_size;
+  assert (offset || mem_offset < block_size);
+  offset += mem_offset % block_size;
+  pthread_mutex_unlock (&disk_cache_lock);
+  ext2_debug ("(%p) = %lld", ptr, offset);
+  return offset;
+}
 
 /* block num --> pointer to in-memory block */
 #define bptr(block) boffs_ptr(boffs(block))
@@ -308,14 +389,24 @@ extern struct ext2_inode *dino (ino_t inum);
 #if defined(__USE_EXTERN_INLINES) || defined(EXT2FS_DEFINE_EI)
 /* Convert an inode number to the dinode on disk. */
 EXT2FS_EI struct ext2_inode *
-dino (ino_t inum)
+dino_ref (ino_t inum)
 {
   unsigned long inodes_per_group = sblock->s_inodes_per_group;
   unsigned long bg_num = (inum - 1) / inodes_per_group;
   unsigned long group_inum = (inum - 1) % inodes_per_group;
-  struct ext2_group_desc *bg = group_desc(bg_num);
+  struct ext2_group_desc *bg = group_desc (bg_num);
   block_t block = bg->bg_inode_table + (group_inum / inodes_per_block);
-  return ((struct ext2_inode *)bptr(block)) + group_inum % inodes_per_block;
+  struct ext2_inode *inode = disk_cache_block_ref (block);
+  inode += group_inum % inodes_per_block;
+  ext2_debug ("(%llu) = %p", inum, inode);
+  return inode;
+}
+
+EXT2FS_EI void
+dino_deref (struct ext2_inode *inode)
+{
+  ext2_debug ("(%p)", inode);
+  disk_cache_block_deref (inode);
 }
 #endif /* Use extern inlines.  */
 
@@ -377,27 +468,38 @@ global_block_modified (block_t block)
 EXT2FS_EI void
 record_global_poke (void *ptr)
 {
-  int boffs = trunc_block (bptr_offs (ptr));
-  global_block_modified (boffs_block (boffs));
-  pokel_add (&global_pokel, boffs_ptr(boffs), block_size);
+  block_t block = boffs_block (bptr_offs (ptr));
+  void *block_ptr = bptr (block);
+  ext2_debug ("(%p = %p)", ptr, block_ptr);
+  assert (disk_cache_block_is_ref (block));
+  global_block_modified (block);
+  pokel_add (&global_pokel, block_ptr, block_size);
 }
 
 /* This syncs a modification to a non-file block.  */
 EXT2FS_EI void
 sync_global_ptr (void *bptr, int wait)
 {
-  vm_offset_t boffs = trunc_block (bptr_offs (bptr));
-  global_block_modified (boffs_block (boffs));
-  pager_sync_some (diskfs_disk_pager, trunc_page (boffs), vm_page_size, wait);
+  block_t block = boffs_block (bptr_offs (bptr));
+  void *block_ptr = bptr (block);
+  ext2_debug ("(%p -> %u)", bptr, block);
+  global_block_modified (block);
+  disk_cache_block_deref (block_ptr);
+  pager_sync_some (diskfs_disk_pager,
+		   block_ptr - disk_cache, block_size, wait);
+
 }
 
 /* This records a modification to one of a file's indirect blocks.  */
 EXT2FS_EI void
 record_indir_poke (struct node *node, void *ptr)
 {
-  int boffs = trunc_block (bptr_offs (ptr));
-  global_block_modified (boffs_block (boffs));
-  pokel_add (&node->dn->indir_pokel, boffs_ptr(boffs), block_size);
+  block_t block = boffs_block (bptr_offs (ptr));
+  void *block_ptr = bptr (block);
+  ext2_debug ("(%llu, %p)", node->cache_id, ptr);
+  assert (disk_cache_block_is_ref (block));
+  global_block_modified (block);
+  pokel_add (&node->dn->indir_pokel, block_ptr, block_size);
 }
 
 /* ---------------------------------------------------------------- */
@@ -405,6 +507,7 @@ record_indir_poke (struct node *node, void *ptr)
 EXT2FS_EI void
 sync_global (int wait)
 {
+  ext2_debug ("%d", wait);
   pokel_sync (&global_pokel, wait);
 }
 
diff --git a/ext2fs/getblk.c b/ext2fs/getblk.c
index 23ba6459..bde66e1c 100644
--- a/ext2fs/getblk.c
+++ b/ext2fs/getblk.c
@@ -104,7 +104,7 @@ ext2_alloc_block (struct node *node, block_t goal, int zero)
 
   if (result && zero)
     {
-      char *bh = bptr (result);
+      char *bh = disk_cache_block_ref (result);
       bzero (bh, block_size);
       record_indir_poke (node, bh);
     }
@@ -122,6 +122,8 @@ inode_getblk (struct node *node, int nr, int create, int zero,
   block_t hint;
 #endif
 
+  assert (0 <= nr && nr < EXT2_N_BLOCKS);
+
   *result = node->dn->info.i_data[nr];
   if (*result)
     return 0;
@@ -180,14 +182,20 @@ block_getblk (struct node *node, block_t block, int nr, int create, int zero,
 {
   int i;
   block_t goal = 0;
-  block_t *bh = (block_t *)bptr (block);
+  block_t *bh = (block_t *)disk_cache_block_ref (block);
 
   *result = bh[nr];
   if (*result)
-    return 0;
+    {
+      disk_cache_block_deref (bh);
+      return 0;
+    }
 
   if (!create)
-    return EINVAL;
+    {
+      disk_cache_block_deref (bh);
+      return EINVAL;
+    }
 
   if (node->dn->info.i_next_alloc_block == new_block)
     goal = node->dn->info.i_next_alloc_goal;
@@ -207,7 +215,10 @@ block_getblk (struct node *node, block_t block, int nr, int create, int zero,
 
   *result = ext2_alloc_block (node, goal, zero);
   if (!*result)
-    return ENOSPC;
+    {
+      disk_cache_block_deref (bh);
+      return ENOSPC;
+    }
 
   bh[nr] = *result;
 
diff --git a/ext2fs/hyper.c b/ext2fs/hyper.c
index bee4175f..5bcc2abe 100644
--- a/ext2fs/hyper.c
+++ b/ext2fs/hyper.c
@@ -58,11 +58,14 @@ static int ext2fs_clean;	/* fs clean before we started writing? */
 void
 get_hypermetadata (void)
 {
-  error_t err = diskfs_catch_exception ();
-  if (err)
-    ext2_panic ("can't read superblock: %s", strerror (err));
+  error_t err;
+  size_t read = 0;
 
-  sblock = (struct ext2_super_block *) boffs_ptr (SBLOCK_OFFS);
+  assert (! sblock);
+  err = store_read (store, SBLOCK_OFFS >> store->log2_block_size,
+		    SBLOCK_SIZE, (void **)&sblock, &read);
+  if (err || read != SBLOCK_SIZE)
+    ext2_panic ("Cannot read hypermetadata");
 
   if (sblock->s_magic != EXT2_SUPER_MAGIC
 #ifdef EXT2FS_PRE_02B_COMPAT
@@ -152,15 +155,25 @@ get_hypermetadata (void)
 
   allocate_mod_map ();
 
-  diskfs_end_catch_exception ();
+  /* A handy source of page-aligned zeros.  */
+  if (zeroblock == 0)
+    {
+      zeroblock = (vm_address_t) mmap (0, block_size, PROT_READ, MAP_ANON, 0, 0);
+      assert (zeroblock != (vm_address_t) MAP_FAILED);
+    }
+
+  munmap (sblock, SBLOCK_SIZE);
+  sblock = NULL;
+}
+
+void
+map_hypermetadata (void)
+{
+  sblock = (struct ext2_super_block *) boffs_ptr (SBLOCK_OFFS);
 
   /* Cache a convenient pointer to the block group descriptors for allocation.
      These are stored in the filesystem blocks following the superblock.  */
   group_desc_image = (struct ext2_group_desc *) bptr (bptr_block (sblock) + 1);
-
-  /* A handy source of page-aligned zeros.  */
-  if (zeroblock == 0)
-    zeroblock = (vm_address_t) mmap (0, block_size, PROT_READ, MAP_ANON, 0, 0);
 }
 
 error_t
@@ -183,6 +196,7 @@ diskfs_set_hypermetadata (int wait, int clean)
  if (sblock_dirty)
    {
      sblock_dirty = 0;
+     disk_cache_block_ref_ptr (sblock);
      record_global_poke (sblock);
    }
 
@@ -199,7 +213,8 @@ diskfs_readonly_changed (int readonly)
 
   (*(readonly ? store_set_flags : store_clear_flags)) (store, STORE_READONLY);
 
-  mprotect (disk_image, store->size, PROT_READ | (readonly ? 0 : PROT_WRITE));
+  mprotect (disk_cache, disk_cache_size,
+	    PROT_READ | (readonly ? 0 : PROT_WRITE));
 
   if (!readonly && !(sblock->s_state & EXT2_VALID_FS))
     ext2_warning ("UNCLEANED FILESYSTEM NOW WRITABLE");
diff --git a/ext2fs/ialloc.c b/ext2fs/ialloc.c
index aa018d94..2d8e51e0 100644
--- a/ext2fs/ialloc.c
+++ b/ext2fs/ialloc.c
@@ -75,22 +75,25 @@ diskfs_free_node (struct node *np, mode_t old_mode)
   bit = (inum - 1) % sblock->s_inodes_per_group;
 
   gdp = group_desc (block_group);
-  bh = bptr (gdp->bg_inode_bitmap);
+  bh = disk_cache_block_ref (gdp->bg_inode_bitmap);
 
   if (!clear_bit (bit, bh))
     ext2_warning ("bit already cleared for inode %Ld", inum);
   else
     {
+      disk_cache_block_ref_ptr (bh);
       record_global_poke (bh);
 
       gdp->bg_free_inodes_count++;
       if (S_ISDIR (old_mode))
 	gdp->bg_used_dirs_count--;
+      disk_cache_block_ref_ptr (gdp);
       record_global_poke (gdp);
 
       sblock->s_free_inodes_count++;
     }
 
+  disk_cache_block_deref (bh);
   sblock_dirty = 1;
   pthread_spin_unlock (&global_lock);
   alloc_sync(0);
@@ -111,7 +114,7 @@ diskfs_free_node (struct node *np, mode_t old_mode)
 ino_t
 ext2_alloc_inode (ino_t dir_inum, mode_t mode)
 {
-  char *bh;
+  char *bh = NULL;
   int i, j, inum, avefreei;
   struct ext2_group_desc *gdp;
   struct ext2_group_desc *tmp;
@@ -119,6 +122,7 @@ ext2_alloc_inode (ino_t dir_inum, mode_t mode)
   pthread_spin_lock (&global_lock);
 
 repeat:
+  assert (bh == NULL);
   gdp = NULL;
   i = 0;
 
@@ -213,7 +217,7 @@ repeat:
       return 0;
     }
 
-  bh = bptr (gdp->bg_inode_bitmap);
+  bh = disk_cache_block_ref (gdp->bg_inode_bitmap);
   if ((inum =
        find_first_zero_bit ((unsigned long *) bh, sblock->s_inodes_per_group))
       < sblock->s_inodes_per_group)
@@ -221,12 +225,17 @@ repeat:
       if (set_bit (inum, bh))
 	{
 	  ext2_warning ("bit already set for inode %d", inum);
+	  disk_cache_block_deref (bh);
+	  bh = NULL;
 	  goto repeat;
 	}
       record_global_poke (bh);
+      bh = NULL;
     }
   else
     {
+      disk_cache_block_deref (bh);
+      bh = NULL;
       if (gdp->bg_free_inodes_count != 0)
 	{
 	  ext2_error ("free inodes count corrupted in group %d", i);
@@ -248,15 +257,25 @@ repeat:
   gdp->bg_free_inodes_count--;
   if (S_ISDIR (mode))
     gdp->bg_used_dirs_count++;
+  disk_cache_block_ref_ptr (gdp);
   record_global_poke (gdp);
 
   sblock->s_free_inodes_count--;
   sblock_dirty = 1;
 
  sync_out:
+  assert (bh == NULL);
   pthread_spin_unlock (&global_lock);
   alloc_sync (0);
 
+  /* Make sure the coming read_node won't complain about bad
+     fields.  */
+  {
+    struct ext2_inode *di = dino_ref (inum);
+    memset (di, 0, sizeof *di);
+    dino_deref (di);
+  }
+
   return inum;
 }
 
@@ -353,10 +372,12 @@ ext2_count_free_inodes ()
   gdp = NULL;
   for (i = 0; i < groups_count; i++)
     {
+      void *bh;
       gdp = group_desc (i);
       desc_count += gdp->bg_free_inodes_count;
-      x = count_free (bptr (gdp->bg_inode_bitmap),
-		      sblock->s_inodes_per_group / 8);
+      bh = disk_cache_block_ref (gdp->bg_inode_bitmap);
+      x = count_free (bh, sblock->s_inodes_per_group / 8);
+      disk_cache_block_deref (bh);
       ext2_debug ("group %d: stored = %d, counted = %lu",
 		  i, gdp->bg_free_inodes_count, x);
       bitmap_count += x;
@@ -386,10 +407,12 @@ ext2_check_inodes_bitmap ()
   gdp = NULL;
   for (i = 0; i < groups_count; i++)
     {
+      void *bh;
       gdp = group_desc (i);
       desc_count += gdp->bg_free_inodes_count;
-      x = count_free (bptr (gdp->bg_inode_bitmap),
-		      sblock->s_inodes_per_group / 8);
+      bh = disk_cache_block_ref (gdp->bg_inode_bitmap);
+      x = count_free (bh, sblock->s_inodes_per_group / 8);
+      disk_cache_block_deref (bh);
       if (gdp->bg_free_inodes_count != x)
 	ext2_error ("wrong free inodes count in group %d, "
 		    "stored = %d, counted = %lu",
diff --git a/ext2fs/inode.c b/ext2fs/inode.c
index 2c442795..e75c63f9 100644
--- a/ext2fs/inode.c
+++ b/ext2fs/inode.c
@@ -92,7 +92,7 @@ diskfs_cached_lookup (ino_t inum, struct node **npp)
   dn->dir_idx = 0;
   dn->pager = 0;
   pthread_rwlock_init (&dn->alloc_lock, NULL);
-  pokel_init (&dn->indir_pokel, diskfs_disk_pager, disk_image);
+  pokel_init (&dn->indir_pokel, diskfs_disk_pager, disk_cache);
 
   /* Create the new node.  */
   np = diskfs_make_node (dn);
@@ -201,13 +201,17 @@ read_node (struct node *np)
   error_t err;
   struct stat *st = &np->dn_stat;
   struct disknode *dn = np->dn;
-  struct ext2_inode *di = dino (np->cache_id);
+  struct ext2_inode *di;
   struct ext2_inode_info *info = &dn->info;
 
+  ext2_debug ("(%llu)", np->cache_id);
+
   err = diskfs_catch_exception ();
   if (err)
     return err;
 
+  di = dino_ref (np->cache_id);
+
   st->st_fstype = FSTYPE_EXT2FS;
   st->st_fsid = getpid ();	/* This call is very cheap.  */
   st->st_ino = np->cache_id;
@@ -285,7 +289,9 @@ read_node (struct node *np)
       info->i_high_size = di->i_size_high;
       if (info->i_high_size)	/* XXX */
 	{
+	  dino_deref (di);
 	  ext2_warning ("cannot handle large file inode %Ld", np->cache_id);
+	  diskfs_end_catch_exception ();
 	  return EFBIG;
 	}
     }
@@ -307,6 +313,7 @@ read_node (struct node *np)
     }
   dn->info_i_translator = di->i_translator;
 
+  dino_deref (di);
   diskfs_end_catch_exception ();
 
   if (S_ISREG (st->st_mode) || S_ISDIR (st->st_mode)
@@ -408,7 +415,9 @@ write_node (struct node *np)
 {
   error_t err;
   struct stat *st = &np->dn_stat;
-  struct ext2_inode *di = dino (np->cache_id);
+  struct ext2_inode *di;
+
+  ext2_debug ("(%llu)", np->cache_id);
 
   if (np->dn->info.i_prealloc_count)
     ext2_discard_prealloc (np);
@@ -425,6 +434,8 @@ write_node (struct node *np)
       if (err)
 	return NULL;
 
+      di = dino_ref (np->cache_id);
+
       di->i_generation = st->st_gen;
 
       /* We happen to know that the stat mode bits are the same
@@ -505,6 +516,7 @@ write_node (struct node *np)
       diskfs_end_catch_exception ();
       np->dn_stat_dirty = 0;
 
+      /* Leave invoking dino_deref (di) to the caller.  */
       return di;
     }
   else
@@ -674,7 +686,7 @@ diskfs_set_translator (struct node *np, const char *name, unsigned namelen,
   if (err)
     return err;
 
-  di = dino (np->cache_id);
+  di = dino_ref (np->cache_id);
   blkno = di->i_translator;
 
   if (namelen && !blkno)
@@ -687,6 +699,7 @@ diskfs_set_translator (struct node *np, const char *name, unsigned namelen,
 			0, 0, 0);
       if (blkno == 0)
 	{
+	  dino_deref (di);
 	  diskfs_end_catch_exception ();
 	  return ENOSPC;
 	}
@@ -710,15 +723,20 @@ diskfs_set_translator (struct node *np, const char *name, unsigned namelen,
       np->dn_stat.st_mode &= ~S_IPTRANS;
       np->dn_set_ctime = 1;
     }
+  else
+    dino_deref (di);
 
   if (namelen)
     {
+      void *blkptr;
+
       buf[0] = namelen & 0xFF;
       buf[1] = (namelen >> 8) & 0xFF;
       bcopy (name, buf + 2, namelen);
 
-      bcopy (buf, bptr (blkno), block_size);
-      record_global_poke (bptr (blkno));
+      blkptr = disk_cache_block_ref (blkno);
+      memcpy (blkptr, buf, block_size);
+      record_global_poke (blkptr);
 
       np->dn_stat.st_mode |= S_IPTRANS;
       np->dn_set_ctime = 1;
@@ -736,7 +754,8 @@ diskfs_get_translator (struct node *np, char **namep, unsigned *namelen)
   error_t err = 0;
   daddr_t blkno;
   unsigned datalen;
-  const void *transloc;
+  void *transloc;
+  struct ext2_inode *di;
 
   assert (sblock->s_creator_os == EXT2_OS_HURD);
 
@@ -744,9 +763,11 @@ diskfs_get_translator (struct node *np, char **namep, unsigned *namelen)
   if (err)
     return err;
 
-  blkno = (dino (np->cache_id))->i_translator;
+  di = dino_ref (np->cache_id);
+  blkno = di->i_translator;
+  dino_deref (di);
   assert (blkno);
-  transloc = bptr (blkno);
+  transloc = disk_cache_block_ref (blkno);
 
   datalen =
     ((unsigned char *)transloc)[0] + (((unsigned char *)transloc)[1] << 8);
@@ -761,6 +782,7 @@ diskfs_get_translator (struct node *np, char **namep, unsigned *namelen)
 	memcpy (*namep, transloc + 2, datalen);
     }
 
+  disk_cache_block_deref (transloc);
   diskfs_end_catch_exception ();
 
   *namelen = datalen;
diff --git a/ext2fs/pager.c b/ext2fs/pager.c
index 92137112..6e99c837 100644
--- a/ext2fs/pager.c
+++ b/ext2fs/pager.c
@@ -18,17 +18,18 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
 
+#include <unistd.h>
 #include <string.h>
 #include <errno.h>
 #include <hurd/store.h>
 #include "ext2fs.h"
 
+/* XXX */
+#include "../libpager/priv.h"
+
 /* A ports bucket to hold pager ports.  */
 struct port_bucket *pager_bucket;
 
-/* Mapped image of the disk.  */
-void *disk_image;
-
 pthread_spinlock_t node_to_page_lock = PTHREAD_SPINLOCK_INITIALIZER;
 
 
@@ -165,6 +166,9 @@ file_pager_read_page (struct node *node, vm_offset_t page,
   block_t pending_blocks = 0;
   int num_pending_blocks = 0;
 
+  ext2_debug ("reading inode %llu page %lu[%u]",
+	      node->cache_id, page, vm_page_size);
+
   /* Read the NUM_PENDING_BLOCKS blocks in PENDING_BLOCKS, into the buffer
      pointed to by BUF (allocating it if necessary) at offset OFFS.  OFFS in
      adjusted by the amount read, and NUM_PENDING_BLOCKS is zeroed.  Any read
@@ -173,7 +177,8 @@ file_pager_read_page (struct node *node, vm_offset_t page,
     {
       if (num_pending_blocks > 0)
 	{
-	  block_t dev_block = pending_blocks << log2_dev_blocks_per_fs_block;
+	  store_offset_t dev_block = (store_offset_t) pending_blocks
+	    << log2_dev_blocks_per_fs_block;
 	  size_t amount = num_pending_blocks << log2_block_size;
 	  /* The buffer we try to read into; on the first read, we pass in a
 	     size of zero, so that the read is guaranteed to allocate a new
@@ -297,7 +302,8 @@ pending_blocks_write (struct pending_blocks *pb)
   if (pb->num > 0)
     {
       error_t err;
-      block_t dev_block = pb->block << log2_dev_blocks_per_fs_block;
+      store_offset_t dev_block = (store_offset_t) pb->block
+	<< log2_dev_blocks_per_fs_block;
       size_t length = pb->num << log2_block_size, amount;
 
       ext2_debug ("writing block %u[%ld]", pb->block, pb->num);
@@ -359,7 +365,7 @@ pending_blocks_add (struct pending_blocks *pb, block_t block)
   return 0;
 }
 
-/* Write one page for the pager backing NODE, at offset PAGE, into BUF.  This
+/* Write one page for the pager backing NODE, at OFFSET, into BUF.  This
    may need to write several filesystem blocks to satisfy one page, and tries
    to consolidate the i/o if possible.  */
 static error_t
@@ -411,12 +417,28 @@ disk_pager_read_page (vm_offset_t page, void **buf, int *writelock)
 {
   error_t err;
   size_t length = vm_page_size, read = 0;
-  vm_size_t dev_end = store->size;
+  store_offset_t offset = page, dev_end = store->size;
+  int index = offset >> log2_block_size;
+
+  pthread_mutex_lock (&disk_cache_lock);
+  offset = ((store_offset_t) disk_cache_info[index].block << log2_block_size)
+    + offset % block_size;
+  disk_cache_info[index].flags |= DC_INCORE;
+  disk_cache_info[index].flags &=~ DC_UNTOUCHED;
+#ifndef NDEBUG
+  disk_cache_info[index].last_read = disk_cache_info[index].block;
+  disk_cache_info[index].last_read_xor
+    = disk_cache_info[index].block ^ DISK_CACHE_LAST_READ_XOR;
+#endif
+  pthread_mutex_unlock (&disk_cache_lock);
+
+  ext2_debug ("(%lld)", offset >> log2_block_size);
 
-  if (page + vm_page_size > dev_end)
-    length = dev_end - page;
+  if (offset + vm_page_size > dev_end)
+    length = dev_end - offset;
 
-  err = store_read (store, page >> store->log2_block_size, length, buf, &read);
+  err = store_read (store, offset >> store->log2_block_size, length,
+		    buf, &read);
   if (read != length)
     return EIO;
   if (!err && length != vm_page_size)
@@ -432,26 +454,38 @@ disk_pager_write_page (vm_offset_t page, void *buf)
 {
   error_t err = 0;
   size_t length = vm_page_size, amount;
-  vm_size_t dev_end = store->size;
+  store_offset_t offset = page, dev_end = store->size;
+  int index = offset >> log2_block_size;
+
+  pthread_mutex_lock (&disk_cache_lock);
+  assert (disk_cache_info[index].block != DC_NO_BLOCK);
+  offset = ((store_offset_t) disk_cache_info[index].block << log2_block_size)
+    + offset % block_size;
+#ifndef NDEBUG			/* Not strictly needed.  */
+  assert ((disk_cache_info[index].last_read ^ DISK_CACHE_LAST_READ_XOR)
+	  == disk_cache_info[index].last_read_xor);
+  assert (disk_cache_info[index].last_read
+	  == disk_cache_info[index].block);
+#endif
+  pthread_mutex_unlock (&disk_cache_lock);
 
-  if (page + vm_page_size > dev_end)
-    length = dev_end - page;
+  if (offset + vm_page_size > dev_end)
+    length = dev_end - offset;
 
-  ext2_debug ("writing disk page %d[%d]", page, length);
+  ext2_debug ("writing disk page %lld[%zu]", offset, length);
 
   STAT_INC (disk_pageouts);
 
   if (modified_global_blocks)
     /* Be picky about which blocks in a page that we write.  */
     {
-      vm_offset_t offs = page;
       struct pending_blocks pb;
 
       pending_blocks_init (&pb, buf);
 
       while (length > 0 && !err)
 	{
-	  block_t block = boffs_block (offs);
+	  block_t block = boffs_block (offset);
 
 	  /* We don't clear the block modified bit here because this paging
 	     write request may not be the same one that actually set the bit,
@@ -469,7 +503,7 @@ disk_pager_write_page (vm_offset_t page, void *buf)
 	    /* Otherwise just skip it.  */
 	    err = pending_blocks_skip (&pb);
 
-	  offs += block_size;
+	  offset += block_size;
 	  length -= block_size;
 	}
 
@@ -478,7 +512,7 @@ disk_pager_write_page (vm_offset_t page, void *buf)
     }
   else
     {
-      err = store_write (store, page >> store->log2_block_size,
+      err = store_write (store, offset >> store->log2_block_size,
 			 buf, length, &amount);
       if (!err && length != amount)
 	err = EIO;
@@ -486,6 +520,18 @@ disk_pager_write_page (vm_offset_t page, void *buf)
 
   return err;
 }
+
+static void
+disk_pager_notify_evict (vm_offset_t page)
+{
+  unsigned long index = page >> log2_block_size;
+
+  ext2_debug ("(block %lu)", index);
+
+  pthread_mutex_lock (&disk_cache_lock);
+  disk_cache_info[index].flags &= ~DC_INCORE;
+  pthread_mutex_unlock (&disk_cache_lock);
+}
 
 /* Satisfy a pager read request for either the disk pager or file pager
    PAGER, to the page at offset PAGE into BUF.  WRITELOCK should be set if
@@ -515,7 +561,8 @@ pager_write_page (struct user_pager_info *pager, vm_offset_t page,
 void
 pager_notify_evict (struct user_pager_info *pager, vm_offset_t page)
 {
-  assert (!"unrequested notification on eviction");
+  if (pager->type == DISK)
+    disk_pager_notify_evict (page);
 }
 
 
@@ -774,6 +821,373 @@ pager_dropweak (struct user_pager_info *p __attribute__ ((unused)))
 {
 }
 
+/* Cached blocks from disk.  */
+void *disk_cache;
+
+/* DISK_CACHE size in bytes and blocks.  */
+store_offset_t disk_cache_size;
+int disk_cache_blocks;
+
+/* block num --> pointer to in-memory block */
+hurd_ihash_t disk_cache_bptr;
+/* Cached blocks' info.  */
+struct disk_cache_info *disk_cache_info;
+/* Hint index for which cache block to reuse next.  */
+int disk_cache_hint;
+/* Lock for these structures.  */
+pthread_mutex_t disk_cache_lock;
+/* Fired when a re-association is done.  */
+pthread_cond_t disk_cache_reassociation;
+
+/* Finish mapping initialization. */
+static void
+disk_cache_init (void)
+{
+  if (block_size != vm_page_size)
+    ext2_panic ("Block size %u != vm_page_size %u",
+		block_size, vm_page_size);
+
+  pthread_mutex_init (&disk_cache_lock, NULL);
+  pthread_cond_init (&disk_cache_reassociation, NULL);
+
+  /* Allocate space for block num -> in-memory pointer mapping.  */
+  if (hurd_ihash_create (&disk_cache_bptr, HURD_IHASH_NO_LOCP))
+    ext2_panic ("Can't allocate memory for disk_pager_bptr");
+
+  /* Allocate space for disk cache blocks' info.  */
+  disk_cache_info = malloc ((sizeof *disk_cache_info) * disk_cache_blocks);
+  if (!disk_cache_info)
+    ext2_panic ("Cannot allocate space for disk cache info");
+
+  /* Initialize disk_cache_info.  */
+  for (int i = 0; i < disk_cache_blocks; i++)
+    {
+      disk_cache_info[i].block = DC_NO_BLOCK;
+      disk_cache_info[i].flags = 0;
+      disk_cache_info[i].ref_count = 0;
+#ifndef NDEBUG
+      disk_cache_info[i].last_read = DC_NO_BLOCK;
+      disk_cache_info[i].last_read_xor
+	= DC_NO_BLOCK ^ DISK_CACHE_LAST_READ_XOR;
+#endif
+    }
+  disk_cache_hint = 0;
+
+  /* Map the superblock and the block group descriptors.  */
+  block_t fixed_first = boffs_block (SBLOCK_OFFS);
+  block_t fixed_last = fixed_first
+    + (round_block ((sizeof *group_desc_image) * groups_count)
+       >> log2_block_size);
+  ext2_debug ("%u-%u\n", fixed_first, fixed_last);
+  assert (fixed_last - fixed_first + 1 <= (block_t)disk_cache_blocks + 3);
+  for (block_t i = fixed_first; i <= fixed_last; i++)
+    {
+      disk_cache_block_ref (i);
+      assert (disk_cache_info[i-fixed_first].block == i);
+      disk_cache_info[i-fixed_first].flags |= DC_FIXED;
+    }
+}
+
+static void
+disk_cache_return_unused (void)
+{
+  int index;
+
+  /* XXX: Touch all pages.  It seems that sometimes GNU Mach "forgets"
+     to notify us about evicted pages.  Disk cache must be
+     unlocked.  */
+  for (vm_offset_t i = 0; i < disk_cache_size; i += vm_page_size)
+    *(volatile char *)(disk_cache + i);
+
+  /* Release some references to cached blocks.  */
+  pokel_sync (&global_pokel, 1);
+
+  /* Return unused pages that are in core.  */
+  int pending_begin = -1, pending_end = -1;
+  pthread_mutex_lock (&disk_cache_lock);
+  for (index = 0; index < disk_cache_blocks; index++)
+    if (! (disk_cache_info[index].flags & (DC_DONT_REUSE & ~DC_INCORE))
+	&& ! disk_cache_info[index].ref_count)
+      {
+	ext2_debug ("return %u -> %d",
+		    disk_cache_info[index].block, index);
+	if (index != pending_end)
+	  {
+	    /* Return previous region, if there is such, ... */
+	    if (pending_end >= 0)
+	      {
+		pthread_mutex_unlock (&disk_cache_lock);
+		pager_return_some (diskfs_disk_pager,
+				   pending_begin * vm_page_size,
+				   (pending_end - pending_begin)
+				   * vm_page_size, 1);
+		pthread_mutex_lock (&disk_cache_lock);
+	      }
+	    /* ... and start new region.  */
+	    pending_begin = index;
+	  }
+	pending_end = index + 1;
+      }
+
+  pthread_mutex_unlock (&disk_cache_lock);
+
+  /* Return last region, if there is such.   */
+  if (pending_end >= 0)
+    pager_return_some (diskfs_disk_pager,
+		       pending_begin * vm_page_size,
+		       (pending_end - pending_begin) * vm_page_size,
+		       1);
+  else
+    {
+      printf ("ext2fs: disk cache is starving\n");
+
+      /* Give it some time.  This should happen rarely.  */
+      sleep (1);
+    }
+}
+
+/* Map block and return pointer to it.  */
+void *
+disk_cache_block_ref (block_t block)
+{
+  int index;
+  void *bptr;
+
+  assert (0 <= block && block < store->size >> log2_block_size);
+
+  ext2_debug ("(%u)", block);
+
+retry_ref:
+  pthread_mutex_lock (&disk_cache_lock);
+
+  bptr = hurd_ihash_find (disk_cache_bptr, block);
+  if (bptr)
+    /* Already mapped.  */
+    {
+      index = bptr_index (bptr);
+
+      /* In process of re-associating?  */
+      if (disk_cache_info[index].flags & DC_UNTOUCHED)
+	{
+	  /* Wait re-association to finish.  */
+	  pthread_cond_wait (&disk_cache_reassociation, &disk_cache_lock);
+	  pthread_mutex_unlock (&disk_cache_lock);
+
+#if 0
+	  printf ("Re-association -- wait finished.\n");
+#endif
+
+	  goto retry_ref;
+	}
+
+      /* Just increment reference and return.  */
+      assert (disk_cache_info[index].ref_count + 1
+	      > disk_cache_info[index].ref_count);
+      disk_cache_info[index].ref_count++;
+
+      ext2_debug ("cached %u -> %d (ref_count = %hu, flags = %#hx, ptr = %p)",
+		  disk_cache_info[index].block, index,
+		  disk_cache_info[index].ref_count,
+		  disk_cache_info[index].flags, bptr);
+
+      pthread_mutex_unlock (&disk_cache_lock);
+
+      return bptr;
+    }
+
+  /* Search for a block that is not in core and is not referenced.  */
+  index = disk_cache_hint;
+  while ((disk_cache_info[index].flags & DC_DONT_REUSE)
+	 || (disk_cache_info[index].ref_count))
+    {
+      ext2_debug ("reject %u -> %d (ref_count = %hu, flags = %#hx)",
+		  disk_cache_info[index].block, index,
+		  disk_cache_info[index].ref_count,
+		  disk_cache_info[index].flags);
+
+      /* Just move to next block.  */
+      index++;
+      if (index >= disk_cache_blocks)
+	index -= disk_cache_blocks;
+
+      /* If we return to where we started, than there is no suitable
+	 block. */
+      if (index == disk_cache_hint)
+	break;
+    }
+
+  /* The next place in the disk cache becomes the current hint.  */
+  disk_cache_hint = index + 1;
+  if (disk_cache_hint >= disk_cache_blocks)
+    disk_cache_hint -= disk_cache_blocks;
+
+  /* Is suitable place found?  */
+  if ((disk_cache_info[index].flags & DC_DONT_REUSE)
+      || disk_cache_info[index].ref_count)
+    /* No place is found.  Try to release some blocks and try
+       again.  */
+    {
+      ext2_debug ("flush %u -> %d", disk_cache_info[index].block, index);
+
+      pthread_mutex_unlock (&disk_cache_lock);
+
+      disk_cache_return_unused ();
+
+      goto retry_ref;
+    }
+
+  /* Suitable place is found.  */
+
+  /* Calculate pointer to data.  */
+  bptr = (char *)disk_cache + (index << log2_block_size);
+  ext2_debug ("map %u -> %d (%p)", block, index, bptr);
+
+  /* This pager_return_some is used only to set PM_FORCEREAD for the
+     page.  DC_UNTOUCHED is set so that we catch if someone has
+     referenced the block while we didn't hold disk_cache_lock.  */
+  disk_cache_info[index].flags |= DC_UNTOUCHED;
+
+#if 0 /* XXX: Let's see if this is needed at all.  */
+
+  pthread_mutex_unlock (&disk_cache_lock);
+  pager_return_some (diskfs_disk_pager, bptr - disk_cache, vm_page_size, 1);
+  pthread_mutex_lock (&disk_cache_lock);
+
+  /* Has someone used our bptr?  Has someone mapped requested block
+     while we have unlocked disk_cache_lock?  If so, environment has
+     changed and we have to restart operation.  */
+  if ((! (disk_cache_info[index].flags & DC_UNTOUCHED))
+      || hurd_ihash_find (disk_cache_bptr, block))
+    {
+      pthread_mutex_unlock (&disk_cache_lock);
+      goto retry_ref;
+    }
+
+#elif 0
+
+  /* XXX: Use libpager internals.  */
+
+  pthread_mutex_lock (&diskfs_disk_pager->interlock);
+  int page = (bptr - disk_cache) / vm_page_size;
+  assert (page >= 0);
+  int is_incore = (page < diskfs_disk_pager->pagemapsize
+		   && (diskfs_disk_pager->pagemap[page] & PM_INCORE));
+  pthread_mutex_unlock (&diskfs_disk_pager->interlock);
+  if (is_incore)
+    {
+      pthread_mutex_unlock (&disk_cache_lock);
+      printf ("INCORE\n");
+      goto retry_ref;
+    }
+
+#endif
+
+  /* Re-associate.  */
+  if (disk_cache_info[index].block != DC_NO_BLOCK)
+    /* Remove old association.  */
+    hurd_ihash_remove (disk_cache_bptr, disk_cache_info[index].block);
+  /* New association.  */
+  if (hurd_ihash_add (disk_cache_bptr, block, bptr))
+    ext2_panic ("Couldn't hurd_ihash_add new disk block");
+  assert (! (disk_cache_info[index].flags & DC_DONT_REUSE & ~DC_UNTOUCHED));
+  disk_cache_info[index].block = block;
+  assert (! disk_cache_info[index].ref_count);
+  disk_cache_info[index].ref_count = 1;
+
+  /* All data structures are set up.  */
+  pthread_mutex_unlock (&disk_cache_lock);
+
+  /* Try to read page.  */
+  *(volatile char *) bptr;
+
+  /* Check if it's actually read.  */
+  pthread_mutex_lock (&disk_cache_lock);
+  if (disk_cache_info[index].flags & DC_UNTOUCHED)
+    /* It's not read.  */
+    {
+      /* Remove newly created association.  */
+      hurd_ihash_remove (disk_cache_bptr, block);
+      disk_cache_info[index].block = DC_NO_BLOCK;
+      disk_cache_info[index].flags &=~ DC_UNTOUCHED;
+      disk_cache_info[index].ref_count = 0;
+      pthread_mutex_unlock (&disk_cache_lock);
+
+      /* Prepare next time association of this page to succeed.  */
+      pager_flush_some (diskfs_disk_pager, bptr - disk_cache,
+			vm_page_size, 0);
+
+#if 0
+      printf ("Re-association failed.\n");
+#endif
+
+      goto retry_ref;
+    }
+
+  /* Re-association was successful.  */
+  pthread_cond_broadcast (&disk_cache_reassociation);
+
+  pthread_mutex_unlock (&disk_cache_lock);
+
+  ext2_debug ("(%u) = %p", block, bptr);
+  return bptr;
+}
+
+void
+disk_cache_block_ref_ptr (void *ptr)
+{
+  int index;
+
+  pthread_mutex_lock (&disk_cache_lock);
+  index = bptr_index (ptr);
+  assert (disk_cache_info[index].ref_count >= 1);
+  assert (disk_cache_info[index].ref_count + 1
+	  > disk_cache_info[index].ref_count);
+  disk_cache_info[index].ref_count++;
+  assert (! (disk_cache_info[index].flags & DC_UNTOUCHED));
+  ext2_debug ("(%p) (ref_count = %hu, flags = %#hx)",
+	      ptr,
+	      disk_cache_info[index].ref_count,
+	      disk_cache_info[index].flags);
+  pthread_mutex_unlock (&disk_cache_lock);
+}
+
+void
+disk_cache_block_deref (void *ptr)
+{
+  int index;
+
+  assert (disk_cache <= ptr && ptr <= disk_cache + disk_cache_size);
+
+  pthread_mutex_lock (&disk_cache_lock);
+  index = bptr_index (ptr);
+  ext2_debug ("(%p) (ref_count = %hu, flags = %#hx)",
+	      ptr,
+	      disk_cache_info[index].ref_count - 1,
+	      disk_cache_info[index].flags);
+  assert (! (disk_cache_info[index].flags & DC_UNTOUCHED));
+  assert (disk_cache_info[index].ref_count >= 1);
+  disk_cache_info[index].ref_count--;
+  pthread_mutex_unlock (&disk_cache_lock);
+}
+
+/* Not used.  */
+int
+disk_cache_block_is_ref (block_t block)
+{
+  int ref;
+  void *ptr;
+
+  pthread_mutex_lock (&disk_cache_lock);
+  ptr = hurd_ihash_find (disk_cache_bptr, block);
+  if (ptr == NULL)
+    ref = 0;
+  else				/* XXX: Should check for DC_UNTOUCHED too.  */
+    ref = disk_cache_info[bptr_index (ptr)].ref_count;
+  pthread_mutex_unlock (&disk_cache_lock);
+
+  return ref;
+}
+
 /* Create the DISK pager.  */
 void
 create_disk_pager (void)
@@ -783,9 +1197,12 @@ create_disk_pager (void)
     ext2_panic ("can't create disk pager: %s", strerror (errno));
   upi->type = DISK;
   pager_bucket = ports_create_bucket ();
-  diskfs_start_disk_pager (upi, pager_bucket, MAY_CACHE, 0,
-			   store->size, &disk_image);
-
+  get_hypermetadata ();
+  disk_cache_blocks = DISK_CACHE_BLOCKS;
+  disk_cache_size = disk_cache_blocks << log2_block_size;
+  diskfs_start_disk_pager (upi, pager_bucket, MAY_CACHE, 1,
+			   disk_cache_size, &disk_cache);
+  disk_cache_init ();
 }
 
 /* Call this to create a FILE_DATA pager and return a send right.
diff --git a/ext2fs/pokel.c b/ext2fs/pokel.c
index a8b16c97..3afb32e4 100644
--- a/ext2fs/pokel.c
+++ b/ext2fs/pokel.c
@@ -67,12 +67,27 @@ pokel_add (struct pokel *pokel, void *loc, vm_size_t length)
       vm_offset_t p_offs = pl->offset;
       vm_size_t p_end = p_offs + pl->length;
 
-      if (p_offs == offset && p_end == end)
-	break;
+      if (p_offs <= offset && end <= p_end)
+	{
+	  if (pokel->image == disk_cache)
+	    for (vm_offset_t i = offset; i < end; i += block_size)
+	      disk_cache_block_deref (disk_cache + i);
+
+	  break;
+	}
       else if (p_end >= offset && end >= p_offs)
 	{
 	  pl->offset = offset < p_offs ? offset : p_offs;
 	  pl->length = (end > p_end ? end : p_end) - pl->offset;
+
+	  if (pokel->image == disk_cache)
+	    {
+	      vm_offset_t i_begin = p_offs > offset ? p_offs : offset;
+	      vm_offset_t i_end = p_end < end ? p_end : end;
+	      for (vm_offset_t i = i_begin; i < i_end; i += block_size)
+		disk_cache_block_deref (disk_cache + i);
+	    }
+
 	  ext2_debug ("extended 0x%x[%ul] to 0x%x[%ul]",
 		      p_offs, p_end - p_offs, pl->offset, pl->length);
 	  break;
@@ -113,11 +128,21 @@ _pokel_exec (struct pokel *pokel, int sync, int wait)
   pthread_spin_unlock (&pokel->lock);
 
   for (pl = pokes; pl; last = pl, pl = pl->next)
-    if (sync)
-      {
-	ext2_debug ("syncing 0x%x[%ul]", pl->offset, pl->length);
-	pager_sync_some (pokel->pager, pl->offset, pl->length, wait);
-      }
+    {
+      if (sync)
+	{
+	  ext2_debug ("syncing 0x%lx[%ul]", pl->offset, pl->length);
+	  pager_sync_some (pokel->pager, pl->offset, pl->length, wait);
+	}
+
+      if (pokel->image == disk_cache)
+	{
+	  vm_offset_t begin = trunc_block (pl->offset);
+	  vm_offset_t end = round_block (pl->offset + pl->length);
+	  for (vm_offset_t i = begin; i != end; i += block_size)
+	    disk_cache_block_deref (pokel->image + i);
+	}
+    }
 
   if (last)
     {
diff --git a/ext2fs/truncate.c b/ext2fs/truncate.c
index 37e360bb..63d22955 100644
--- a/ext2fs/truncate.c
+++ b/ext2fs/truncate.c
@@ -124,7 +124,7 @@ trunc_indirect (struct node *node, block_t end,
     {
       unsigned index;
       int modified = 0, all_freed = 1;
-      block_t *ind_bh = (block_t *)bptr (*p);
+      block_t *ind_bh = (block_t *) disk_cache_block_ref (*p);
       unsigned first = end < offset ? 0 : end - offset;
 
       for (index = first; index < addr_per_block; index++)
@@ -139,11 +139,16 @@ trunc_indirect (struct node *node, block_t end,
 
       if (first == 0 && all_freed)
 	{
-	  pager_flush_some (diskfs_disk_pager, boffs (*p), block_size, 1);
+	  pager_flush_some (diskfs_disk_pager,
+			    bptr_index (ind_bh) << log2_block_size,
+			    block_size, 1);
 	  free_block_run_free_ptr (fbr, p);
+	  disk_cache_block_deref (ind_bh);
 	}
       else if (modified)
 	record_indir_poke (node, ind_bh);
+      else
+	disk_cache_block_deref (ind_bh);
     }
 }