libext2fs: Implement ext2fs_find_first_zero_generic_bmap().

This function searches a bitmap for the first zero bit within a range.
It checks if there is a bitmap backend specific implementation
available (if the relevant field in bitmap_ops is non-NULL). If not,
it uses a generic and slow method by repeatedly calling test_bmap() in
a loop. Also change ext2fs_new_inode() to use this new function.

This change in itself does not result in a large speedup, rather it
refactors the code in preparation for the introduction of a faster
find_first_zero() for bitarray based bitmaps.

Signed-off-by: Sami Liedes <sami.liedes@iki.fi>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/lib/ext2fs/alloc.c b/lib/ext2fs/alloc.c
index bcdc2d4..752c4da 100644 (file)
--- a/lib/ext2fs/alloc.c
+++ b/lib/ext2fs/alloc.c
@@ -106,10 +106,10 @@ errcode_t ext2fs_new_inode(ext2_filsys fs, ext2_ino_t dir,
                           int mode EXT2FS_ATTR((unused)),
                           ext2fs_inode_bitmap map, ext2_ino_t *ret)
 {
-       ext2_ino_t      dir_group = 0;
-       ext2_ino_t      i;
-       ext2_ino_t      start_inode;
-       ext2_ino_t      ino_in_group;
+       ext2_ino_t      start_inode = 0;
+       ext2_ino_t      i, ino_in_group, upto, first_zero;
+       errcode_t       retval;
+       dgrp_t          group;
 
        EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 
@@ -118,31 +118,37 @@ errcode_t ext2fs_new_inode(ext2_filsys fs, ext2_ino_t dir,
        if (!map)
                return EXT2_ET_NO_INODE_BITMAP;
 
-       if (dir > 0)
-               dir_group = (dir - 1) / EXT2_INODES_PER_GROUP(fs->super);
-
-       start_inode = (dir_group * EXT2_INODES_PER_GROUP(fs->super)) + 1;
+       if (dir > 0) {
+               group = (dir - 1) / EXT2_INODES_PER_GROUP(fs->super);
+               start_inode = (group * EXT2_INODES_PER_GROUP(fs->super)) + 1;
+       }
        if (start_inode < EXT2_FIRST_INODE(fs->super))
                start_inode = EXT2_FIRST_INODE(fs->super);
        if (start_inode > fs->super->s_inodes_count)
                return EXT2_ET_INODE_ALLOC_FAIL;
        i = start_inode;
-       ino_in_group = (i - 1) % EXT2_INODES_PER_GROUP(fs->super);
-
        do {
-               if (ino_in_group == 0)
-                       check_inode_uninit(fs, map, (i - 1) /
-                                          EXT2_INODES_PER_GROUP(fs->super));
-
-               if (!ext2fs_fast_test_inode_bitmap2(map, i))
+               ino_in_group = (i - 1) % EXT2_INODES_PER_GROUP(fs->super);
+               group = (i - 1) / EXT2_INODES_PER_GROUP(fs->super);
+
+               check_inode_uninit(fs, map, group);
+               upto = i + (EXT2_INODES_PER_GROUP(fs->super) - ino_in_group);
+               if (i < start_inode && upto >= start_inode)
+                       upto = start_inode - 1;
+               if (upto > fs->super->s_inodes_count)
+                       upto = fs->super->s_inodes_count;
+
+               retval = ext2fs_find_first_zero_inode_bitmap2(map, i, upto,
+                                                             &first_zero);
+               if (retval == 0) {
+                       i = first_zero;
                        break;
-               if (++ino_in_group == EXT2_INODES_PER_GROUP(fs->super))
-                       ino_in_group = 0;
-               if (++i > fs->super->s_inodes_count) {
-                       i = EXT2_FIRST_INODE(fs->super);
-                       ino_in_group = ((i - 1) % 
-                                       EXT2_INODES_PER_GROUP(fs->super));
                }
+               if (retval != ENOENT)
+                       return EXT2_ET_INODE_ALLOC_FAIL;
+               i = upto + 1;
+               if (i > fs->super->s_inodes_count)
+                       i = EXT2_FIRST_INODE(fs->super);
        } while (i != start_inode);
 
        if (ext2fs_test_inode_bitmap2(map, i))

diff --git a/lib/ext2fs/bitops.h b/lib/ext2fs/bitops.h
index 83a01e4..9382790 100644 (file)
--- a/lib/ext2fs/bitops.h
+++ b/lib/ext2fs/bitops.h
@@ -152,6 +152,14 @@ extern void ext2fs_fast_unmark_inode_bitmap2(ext2fs_inode_bitmap bitmap,
                                            ext2_ino_t inode);
 extern int ext2fs_fast_test_inode_bitmap2(ext2fs_inode_bitmap bitmap,
                                          ext2_ino_t inode);
+extern errcode_t ext2fs_find_first_zero_block_bitmap2(ext2fs_block_bitmap bitmap,
+                                                     ext2_ino_t start,
+                                                     ext2_ino_t end,
+                                                     ext2_ino_t *out);
+extern errcode_t ext2fs_find_first_zero_inode_bitmap2(ext2fs_inode_bitmap bitmap,
+                                                     ext2_ino_t start,
+                                                     ext2_ino_t end,
+                                                     ext2_ino_t *out);
 extern blk64_t ext2fs_get_block_bitmap_start2(ext2fs_block_bitmap bitmap);
 extern ext2_ino_t ext2fs_get_inode_bitmap_start2(ext2fs_inode_bitmap bitmap);
 extern blk64_t ext2fs_get_block_bitmap_end2(ext2fs_block_bitmap bitmap);
@@ -188,6 +196,9 @@ extern void ext2fs_mark_block_bitmap_range2(ext2fs_block_bitmap bitmap,
                                            blk64_t block, unsigned int num);
 extern void ext2fs_unmark_block_bitmap_range2(ext2fs_block_bitmap bitmap,
                                              blk64_t block, unsigned int num);
+extern errcode_t ext2fs_find_first_zero_generic_bmap(ext2fs_generic_bitmap bitmap,
+                                                    __u64 start, __u64 end,
+                                                    __u64 *out);
 
 /*
  * The inline routines themselves...
@@ -593,6 +604,36 @@ _INLINE_ int ext2fs_fast_test_inode_bitmap2(ext2fs_inode_bitmap bitmap,
                                        inode);
 }
 
+_INLINE_ errcode_t ext2fs_find_first_zero_block_bitmap2(ext2fs_block_bitmap bitmap,
+                                                       ext2_ino_t start,
+                                                       ext2_ino_t end,
+                                                       ext2_ino_t *out)
+{
+       __u64 o;
+       errcode_t rv;
+
+       rv = ext2fs_find_first_zero_generic_bmap((ext2fs_generic_bitmap) bitmap,
+                                                start, end, &o);
+       if (!rv)
+               *out = o;
+       return rv;
+}
+
+_INLINE_ errcode_t ext2fs_find_first_zero_inode_bitmap2(ext2fs_inode_bitmap bitmap,
+                                                       ext2_ino_t start,
+                                                       ext2_ino_t end,
+                                                       ext2_ino_t *out)
+{
+       __u64 o;
+       errcode_t rv;
+
+       rv = ext2fs_find_first_zero_generic_bmap((ext2fs_generic_bitmap) bitmap,
+                                                start, end, &o);
+       if (!rv)
+               *out = o;
+       return rv;
+}
+
 _INLINE_ blk64_t ext2fs_get_block_bitmap_start2(ext2fs_block_bitmap bitmap)
 {
        return ext2fs_get_generic_bmap_start((ext2fs_generic_bitmap) bitmap);

diff --git a/lib/ext2fs/bmap64.h b/lib/ext2fs/bmap64.h
index 288e1b6..f44d379 100644 (file)
--- a/lib/ext2fs/bmap64.h
+++ b/lib/ext2fs/bmap64.h
@@ -89,6 +89,11 @@ struct ext2_bitmap_ops {
                                    __u64 start, size_t num, void *out);
        void (*clear_bmap)(ext2fs_generic_bitmap bitmap);
        void (*print_stats)(ext2fs_generic_bitmap);
+
+       /* Find the first zero bit between start and end, inclusive.
+        * May be NULL, in which case a generic function is used. */
+       errcode_t (*find_first_zero)(ext2fs_generic_bitmap bitmap,
+                                    __u64 start, __u64 end, __u64 *out);
 };
 
 extern struct ext2_bitmap_ops ext2fs_blkmap64_bitarray;

diff --git a/lib/ext2fs/gen_bitmap64.c b/lib/ext2fs/gen_bitmap64.c
index fa8d7b7..b57df54 100644 (file)
--- a/lib/ext2fs/gen_bitmap64.c
+++ b/lib/ext2fs/gen_bitmap64.c
@@ -762,3 +762,31 @@ errcode_t ext2fs_convert_subcluster_bitmap(ext2_filsys fs,
        *bitmap = cmap;
        return 0;
 }
+
+errcode_t ext2fs_find_first_zero_generic_bmap(ext2fs_generic_bitmap bitmap,
+                                             __u64 start, __u64 end, __u64 *out)
+{
+       int b;
+
+       if (bitmap->bitmap_ops->find_first_zero)
+               return bitmap->bitmap_ops->find_first_zero(bitmap, start, end, out);
+
+       if (!bitmap || !EXT2FS_IS_64_BITMAP(bitmap) || bitmap->cluster_bits)
+               return EINVAL;
+
+       if (start < bitmap->start || end > bitmap->end || start > end) {
+               warn_bitmap(bitmap, EXT2FS_TEST_ERROR, start);
+               return EINVAL;
+       }
+
+       while (start <= end) {
+               b = bitmap->bitmap_ops->test_bmap(bitmap, start);
+               if (!b) {
+                       *out = start;
+                       return 0;
+               }
+               start++;
+       }
+
+       return ENOENT;
+}