Avoid mixing cluster numbers and sector numbers. Makes code more readable.

Obtained from:	NetBSD
MFC after:	2 weeks

diff --git a/sbin/fsck_msdosfs/boot.c b/sbin/fsck_msdosfs/boot.c
index 5816b986f694ce8e26ea57ad4c5028789e0a168e..61920e68af522fdc6ae1cd5c4d7863b1d22a65e1 100644 (file)
--- a/sbin/fsck_msdosfs/boot.c
+++ b/sbin/fsck_msdosfs/boot.c
@@ -259,12 +259,18 @@ readboot(int dosfs, struct bootblock *boot)
                return FSFATAL;
        }
 
-       boot->ClusterOffset = (boot->bpbRootDirEnts * 32 +
+       boot->FirstCluster = (boot->bpbRootDirEnts * 32 +
            boot->bpbBytesPerSec - 1) / boot->bpbBytesPerSec +
-           boot->bpbResSectors + boot->bpbFATs * boot->FATsecs -
-           CLUST_FIRST * boot->bpbSecPerClust;
-       boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) /
-           boot->bpbSecPerClust;
+           boot->bpbResSectors + boot->bpbFATs * boot->FATsecs;
+
+       if (boot->FirstCluster + boot->bpbSecPerClust > boot->NumSectors) {
+               pfatal("Cluster offset too large (%u clusters)\n",
+                   boot->FirstCluster);
+               return FSFATAL;
+       }
+
+       boot->NumClusters = (boot->NumSectors - boot->FirstCluster) / boot->bpbSecPerClust +
+           CLUST_FIRST;
 
        if (boot->flags & FAT32)
                boot->ClustMask = CLUST32_MASK;

diff --git a/sbin/fsck_msdosfs/dir.c b/sbin/fsck_msdosfs/dir.c
index 2163db049facd53e3ae57ee472e99d3ad03e76fb..7e459c75d4ffbaece0cb5e649952b2cd14977ae5 100644 (file)
--- a/sbin/fsck_msdosfs/dir.c
+++ b/sbin/fsck_msdosfs/dir.c
@@ -317,7 +317,8 @@ delete(int f, struct bootblock *boot, struct fatEntry *fat, cl_t startcl,
                                break;
                        e = delbuf + endoff;
                }
-               off = startcl * boot->bpbSecPerClust + boot->ClusterOffset;
+               off = (startcl - CLUST_FIRST) * boot->bpbSecPerClust + boot->FirstCluster;
+
                off *= boot->bpbBytesPerSec;
                if (lseek(f, off, SEEK_SET) != off) {
                        perr("Unable to lseek to %" PRId64, off);
@@ -457,7 +458,7 @@ check_subdirectory(int f, struct bootblock *boot, struct dosDirEntry *dir)
                off = boot->bpbResSectors + boot->bpbFATs *
                        boot->FATsecs;
        } else {
-               off = cl * boot->bpbSecPerClust + boot->ClusterOffset;
+               off = (cl - CLUST_FIRST) * boot->bpbSecPerClust + boot->FirstCluster;
        }
 
        /*
@@ -538,7 +539,7 @@ readDosDirSection(int f, struct bootblock *boot, struct fatEntry *fat,
                            boot->FATsecs;
                } else {
                        last = boot->bpbSecPerClust * boot->bpbBytesPerSec;
-                       off = cl * boot->bpbSecPerClust + boot->ClusterOffset;
+                       off = (cl - CLUST_FIRST) * boot->bpbSecPerClust + boot->FirstCluster;
                }
 
                off *= boot->bpbBytesPerSec;
@@ -1069,8 +1070,9 @@ reconnect(int dosfs, struct bootblock *boot, struct fatEntry *fat, cl_t head)
                        lfcl = (lostDir->head < boot->NumClusters) ? lostDir->head : 0;
                        return FSERROR;
                }
-               lfoff = lfcl * boot->ClusterSize
-                   + boot->ClusterOffset * boot->bpbBytesPerSec;
+               lfoff = (lfcl - CLUST_FIRST) * boot->ClusterSize
+                   + boot->FirstCluster * boot->bpbBytesPerSec;
+
                if (lseek(dosfs, lfoff, SEEK_SET) != lfoff
                    || (size_t)read(dosfs, lfbuf, boot->ClusterSize) != boot->ClusterSize) {
                        perr("could not read LOST.DIR");

diff --git a/sbin/fsck_msdosfs/dosfs.h b/sbin/fsck_msdosfs/dosfs.h
index 3d84ea01519ea9e49ca5d68f21ad72674954b60a..9f1480f17b003638f787423e667f73378f87e50e 100644 (file)
--- a/sbin/fsck_msdosfs/dosfs.h
+++ b/sbin/fsck_msdosfs/dosfs.h
@@ -74,7 +74,7 @@ struct bootblock {
        u_int32_t NumSectors;           /* how many sectors are there */
        u_int32_t FATsecs;              /* how many sectors are in FAT */
        u_int32_t NumFatEntries;        /* how many entries really are there */
-       u_int   ClusterOffset;          /* at what sector would sector 0 start */
+       u_int   FirstCluster;           /* at what sector is Cluster CLUST_FIRST */
        u_int   ClusterSize;            /* Cluster size in bytes */
 
        /* Now some statistics: */