fs/adfs: map: incorporate map offsets into layout

lookup_zone() and scan_free_map() cope in different ways with the
location of the map data within a zone:

1. lookup_zone() adds a four byte offset to the map data pointer to
   skip over the check and free link bytes.

2. scan_free_map() needs to use the free link pointer, which is an
   offset from itself, so we end up adding a 32-bit offset to the
   end pointer (aka mapsize) which is really confusing.

Rename mapsize to endbit as this is really what it is, and incorporate
the 32-bit offset into the map layout.  This means that both dm_startbit
and dm_endbit are now bit offsets from the start of the buffer, rather
than four bytes in to the buffer.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/adfs/map.c b/fs/adfs/map.c
index 8ba8877110ffecbb6d365871d12b47c1a7dc0c62..55bd7c20158ccfdc713e288c9fa252a07a23cde3 100644 (file)
--- a/fs/adfs/map.c
+++ b/fs/adfs/map.c
@@ -68,9 +68,9 @@ static DEFINE_RWLOCK(adfs_map_lock);
 static int lookup_zone(const struct adfs_discmap *dm, const unsigned int idlen,
                       const u32 frag_id, unsigned int *offset)
 {
-       const unsigned int mapsize = dm->dm_endbit;
+       const unsigned int endbit = dm->dm_endbit;
        const u32 idmask = (1 << idlen) - 1;
-       unsigned char *map = dm->dm_bh->b_data + 4;
+       unsigned char *map = dm->dm_bh->b_data;
        unsigned int start = dm->dm_startbit;
        unsigned int mapptr;
        u32 frag;
@@ -87,7 +87,7 @@ static int lookup_zone(const struct adfs_discmap *dm, const unsigned int idlen,
                        u32 v = le32_to_cpu(_map[mapptr >> 5]) >> (mapptr & 31);
                        while (v == 0) {
                                mapptr = (mapptr & ~31) + 32;
-                               if (mapptr >= mapsize)
+                               if (mapptr >= endbit)
                                        goto error;
                                v = le32_to_cpu(_map[mapptr >> 5]);
                        }
@@ -99,7 +99,7 @@ static int lookup_zone(const struct adfs_discmap *dm, const unsigned int idlen,
                        goto found;
 again:
                start = mapptr;
-       } while (mapptr < mapsize);
+       } while (mapptr < endbit);
        return -1;
 
 error:
@@ -127,7 +127,7 @@ found:
 static unsigned int
 scan_free_map(struct adfs_sb_info *asb, struct adfs_discmap *dm)
 {
-       const unsigned int mapsize = dm->dm_endbit + 32;
+       const unsigned int endbit = dm->dm_endbit;
        const unsigned int idlen  = asb->s_idlen;
        const unsigned int frag_idlen = idlen <= 15 ? idlen : 15;
        const u32 idmask = (1 << frag_idlen) - 1;
@@ -165,7 +165,7 @@ scan_free_map(struct adfs_sb_info *asb, struct adfs_discmap *dm)
                        u32 v = le32_to_cpu(_map[mapptr >> 5]) >> (mapptr & 31);
                        while (v == 0) {
                                mapptr = (mapptr & ~31) + 32;
-                               if (mapptr >= mapsize)
+                               if (mapptr >= endbit)
                                        goto error;
                                v = le32_to_cpu(_map[mapptr >> 5]);
                        }
@@ -345,19 +345,19 @@ static void adfs_map_layout(struct adfs_discmap *dm, unsigned int nzones,
 
        dm[0].dm_bh       = NULL;
        dm[0].dm_startblk = 0;
-       dm[0].dm_startbit = ADFS_DR_SIZE_BITS;
-       dm[0].dm_endbit   = zone_size;
+       dm[0].dm_startbit = 32 + ADFS_DR_SIZE_BITS;
+       dm[0].dm_endbit   = 32 + zone_size;
 
        for (zone = 1; zone < nzones; zone++) {
                dm[zone].dm_bh       = NULL;
                dm[zone].dm_startblk = zone * zone_size - ADFS_DR_SIZE_BITS;
-               dm[zone].dm_startbit = 0;
-               dm[zone].dm_endbit   = zone_size;
+               dm[zone].dm_startbit = 32;
+               dm[zone].dm_endbit   = 32 + zone_size;
        }
 
        size = adfs_disc_size(dr) >> dr->log2bpmb;
        size -= (nzones - 1) * zone_size - ADFS_DR_SIZE_BITS;
-       dm[nzones - 1].dm_endbit = size;
+       dm[nzones - 1].dm_endbit = 32 + size;
 }
 
 static int adfs_map_read(struct adfs_discmap *dm, struct super_block *sb,