diff options
Diffstat (limited to 'ext2fs/pager.c')
| -rw-r--r-- | ext2fs/pager.c | 83 |
1 files changed, 52 insertions, 31 deletions
diff --git a/ext2fs/pager.c b/ext2fs/pager.c index f28bcabc..47c5f947 100644 --- a/ext2fs/pager.c +++ b/ext2fs/pager.c @@ -840,13 +840,50 @@ int disk_cache_blocks; 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; +/* Linked list of potentially unused blocks. */ +static struct disk_cache_info *disk_cache_info_free; +static pthread_mutex_t disk_cache_info_free_lock; + +/* Get a reusable entry. Must be called with disk_cache_lock + held. */ +static struct disk_cache_info * +disk_cache_info_free_pop (void) +{ + struct disk_cache_info *p; + + do + { + pthread_mutex_lock (&disk_cache_info_free_lock); + p = disk_cache_info_free; + if (p) + { + disk_cache_info_free = p->next; + p->next = NULL; + } + pthread_mutex_unlock (&disk_cache_info_free_lock); + } + while (p && (p->flags & DC_DONT_REUSE || p->ref_count > 0)); + return p; +} + +/* Add P to the list of potentially re-usable entries. */ +static void +disk_cache_info_free_push (struct disk_cache_info *p) +{ + pthread_mutex_lock (&disk_cache_info_free_lock); + if (! p->next) + { + p->next = disk_cache_info_free; + disk_cache_info_free = p; + } + pthread_mutex_unlock (&disk_cache_info_free_lock); +} + /* Finish mapping initialization. */ static void disk_cache_init (void) @@ -857,6 +894,7 @@ disk_cache_init (void) pthread_mutex_init (&disk_cache_lock, NULL); pthread_cond_init (&disk_cache_reassociation, NULL); + pthread_mutex_init (&disk_cache_info_free_lock, NULL); /* Allocate space for block num -> in-memory pointer mapping. */ if (hurd_ihash_create (&disk_cache_bptr, HURD_IHASH_NO_LOCP)) @@ -867,19 +905,22 @@ disk_cache_init (void) 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++) + /* Initialize disk_cache_info. Start with the last entry so that + the first ends up at the front of the free list. This keeps the + assertions at the end of this function happy. */ + for (int i = disk_cache_blocks; i >= 0; i--) { disk_cache_info[i].block = DC_NO_BLOCK; disk_cache_info[i].flags = 0; disk_cache_info[i].ref_count = 0; + disk_cache_info[i].next = NULL; + disk_cache_info_free_push (&disk_cache_info[i]); #ifdef DEBUG_DISK_CACHE 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); @@ -958,6 +999,7 @@ disk_cache_return_unused (void) void * disk_cache_block_ref (block_t block) { + struct disk_cache_info *info; int index; void *bptr; hurd_ihash_locp_t slot; @@ -1005,34 +1047,10 @@ retry_ref: } /* 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; + info = disk_cache_info_free_pop (); /* Is suitable place found? */ - if ((disk_cache_info[index].flags & DC_DONT_REUSE) - || disk_cache_info[index].ref_count) + if (info == NULL) /* No place is found. Try to release some blocks and try again. */ { @@ -1046,6 +1064,7 @@ retry_ref: } /* Suitable place is found. */ + index = info - disk_cache_info; /* Calculate pointer to data. */ bptr = (char *)disk_cache + (index << log2_block_size); @@ -1177,6 +1196,8 @@ disk_cache_block_deref (void *ptr) assert (! (disk_cache_info[index].flags & DC_UNTOUCHED)); assert (disk_cache_info[index].ref_count >= 1); disk_cache_info[index].ref_count--; + if (disk_cache_info[index].ref_count == 0) + disk_cache_info_free_push (&disk_cache_info[index]); pthread_mutex_unlock (&disk_cache_lock); } |