libext2fs: Make icount use a 32-bit counter

In order to more accurately count the number of directories, which
with the DIR_NLINKS feature can now be greater than 65,000, change
icount to use a 32-bit counter.  This doesn't cost us anything extra
when the icount data structures are stored in memory, since due to
padding for alignment reasons.

If the actual count is greater than 65,500, we return 65,500.  This is
because e2fsck doesn't actually need to know the exact count; it only
needs to know if the number of subdirectories is greater than 65,000.
In the future if someone really needs to know the exact number, we
could add a 32-bit interface.  One isn't needed now, though.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/lib/ext2fs/icount.c b/lib/ext2fs/icount.c
index 2905676..bec0f5f 100644 (file)
--- a/lib/ext2fs/icount.c
+++ b/lib/ext2fs/icount.c
@@ -43,7 +43,7 @@
 
 struct ext2_icount_el {
        ext2_ino_t      ino;
-       __u16   count;
+       __u32           count;
 };
 
 struct ext2_icount {
@@ -60,6 +60,15 @@ struct ext2_icount {
        TDB_CONTEXT             *tdb;
 };
 
+/*
+ * We now use a 32-bit counter field because it doesn't cost us
+ * anything extra for the in-memory data structure, due to alignment
+ * padding.  But there's no point changing the interface if most of
+ * the time we only care if the number is bigger than 65,000 or not.
+ * So use the following translation function to return a 16-bit count.
+ */
+#define icount_16_xlate(x) (((x) > 65500) ? 65500 : (x))
+
 void ext2fs_free_icount(ext2_icount_t icount)
 {
        if (!icount)
@@ -398,7 +407,7 @@ static struct ext2_icount_el *get_icount_el(ext2_icount_t icount,
 }
 
 static errcode_t set_inode_count(ext2_icount_t icount, ext2_ino_t ino,
-                                __u16 count)
+                                __u32 count)
 {
        struct ext2_icount_el   *el;
        TDB_DATA key, data;
@@ -407,7 +416,7 @@ static errcode_t set_inode_count(ext2_icount_t icount, ext2_ino_t ino,
                key.dptr = (unsigned char *) &ino;
                key.dsize = sizeof(ext2_ino_t);
                data.dptr = (unsigned char *) &count;
-               data.dsize = sizeof(__u16);
+               data.dsize = sizeof(__u32);
                if (count) {
                        if (tdb_store(icount->tdb, key, data, TDB_REPLACE))
                                return tdb_error(icount->tdb) +
@@ -429,7 +438,7 @@ static errcode_t set_inode_count(ext2_icount_t icount, ext2_ino_t ino,
 }
 
 static errcode_t get_inode_count(ext2_icount_t icount, ext2_ino_t ino,
-                                __u16 *count)
+                                __u32 *count)
 {
        struct ext2_icount_el   *el;
        TDB_DATA key, data;
@@ -444,7 +453,7 @@ static errcode_t get_inode_count(ext2_icount_t icount, ext2_ino_t ino,
                        return tdb_error(icount->tdb) + EXT2_ET_TDB_SUCCESS;
                }
 
-               *count = *((__u16 *) data.dptr);
+               *count = *((__u32 *) data.dptr);
                free(data.dptr);
                return 0;
        }
@@ -483,6 +492,7 @@ errcode_t ext2fs_icount_validate(ext2_icount_t icount, FILE *out)
 
 errcode_t ext2fs_icount_fetch(ext2_icount_t icount, ext2_ino_t ino, __u16 *ret)
 {
+       __u32   val;
        EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);
 
        if (!ino || (ino > icount->num_inodes))
@@ -497,14 +507,15 @@ errcode_t ext2fs_icount_fetch(ext2_icount_t icount, ext2_ino_t ino, __u16 *ret)
                *ret = 0;
                return 0;
        }
-       get_inode_count(icount, ino, ret);
+       get_inode_count(icount, ino, &val);
+       *ret = icount_16_xlate(val);
        return 0;
 }
 
 errcode_t ext2fs_icount_increment(ext2_icount_t icount, ext2_ino_t ino,
                                  __u16 *ret)
 {
-       __u16                   curr_value;
+       __u32                   curr_value;
 
        EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);
 
@@ -554,14 +565,14 @@ errcode_t ext2fs_icount_increment(ext2_icount_t icount, ext2_ino_t ino,
        if (icount->multiple)
                ext2fs_mark_inode_bitmap(icount->multiple, ino);
        if (ret)
-               *ret = curr_value;
+               *ret = icount_16_xlate(curr_value);
        return 0;
 }
 
 errcode_t ext2fs_icount_decrement(ext2_icount_t icount, ext2_ino_t ino,
                                  __u16 *ret)
 {
-       __u16                   curr_value;
+       __u32                   curr_value;
 
        if (!ino || (ino > icount->num_inodes))
                return EXT2_ET_INVALID_ARGUMENT;
@@ -597,7 +608,7 @@ errcode_t ext2fs_icount_decrement(ext2_icount_t icount, ext2_ino_t ino,
                ext2fs_unmark_inode_bitmap(icount->multiple, ino);
 
        if (ret)
-               *ret = curr_value;
+               *ret = icount_16_xlate(curr_value);
        return 0;
 }