vfs: room for 32 disks and partitions, 32 mounts, 16 SchFS volumes

NBLKDEV was 16 for every disk and partition together, which a laptop's
NVMe drive with its eight partitions and a USB stick come close to. The
mount table held 8, SchFS 4 volumes and 4 snapshots, FAT 4 volumes.
Now 32, 32, 16, 8 and 8; the device numbers still fit between the ones
already fixed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4

include/blkdev.h

@@ -15,7 +15,9 @@
 // a Linux driver for SchFS will see when it is handed /dev/sda2.
 
 #define BLKDEV_FIRST   4
-#define NBLKDEV       16        // so device numbers stay below SCHFS_DEV (64)
+// Disks and partitions together. A laptop's NVMe drive alone often carries
+// eight partitions, and a stick or an SD card more, so 16 ran out.
+#define NBLKDEV       32        // device numbers 4..35, below SCHFS_DEV (64)
 
 // The GPT partition type of a SchFS volume, as it is written and printed:
 // 47138FA9-B79C-47A6-9F7D-AC1F7F572D5E. sgdisk and fdisk accept it as is.

include/fat.h

@@ -9,7 +9,7 @@
 
 // Filesystem device numbers for mounted FAT volumes. Like SCHFS_DEV, runtime
 // identities for the inode cache that nothing on disk records.
-#define FAT_VOL_SLOTS 4
+#define FAT_VOL_SLOTS 8    // 104..111
 #define FAT_DEV       104
 #define FAT_IS_DEV(d) ((d) >= FAT_DEV && (d) < FAT_DEV + FAT_VOL_SLOTS)
 

include/file.h

@@ -139,7 +139,8 @@ struct inode {
 // /dev/hdb /mnt` ignored its source argument entirely and handed back whichever
 // disk the kernel had found at boot. Slot 0 is that boot volume, which is why
 // SCHFS_DEV alone still means "the root" everywhere that only ever wanted it.
-#define SCHFS_VOL_SLOTS 4
+// Sixteen, which fills 64..79 up to PROCFS_DEV.
+#define SCHFS_VOL_SLOTS 16
 #define SCHFS_DEV       64
 #define SCHFS_IS_VOL_DEV(d) \
     ((d) >= SCHFS_DEV && (d) < SCHFS_DEV + SCHFS_VOL_SLOTS)
@@ -152,10 +153,10 @@ struct inode {
 // a reader whichever was cached first. So a slot is a device: SCHFS_SNAP_DEV
 // through SCHFS_SNAP_DEV + SCHFS_SNAP_SLOTS - 1.
 //
-// Four rather than one because "one at a time" is an odd thing to explain and
+// More than one because "one at a time" is an odd thing to explain and
-// the cost is two scratch pages per slot, allocated on first use. Four rather
+// the cost is two scratch pages per slot, allocated on first use. Not many
-// than many because each is a device number and they are a fixed, small space.
+// because each is a device number and they are a fixed, small space.
-#define SCHFS_SNAP_SLOTS 4
+#define SCHFS_SNAP_SLOTS 8   // 96..103, up to FAT_DEV
 #define SCHFS_SNAP_DEV   96
 #define SCHFS_IS_SNAP_DEV(d) \
     ((d) >= SCHFS_SNAP_DEV && (d) < SCHFS_SNAP_DEV + SCHFS_SNAP_SLOTS)

kernel/dev/procfs.c

@@ -245,7 +245,7 @@ gen_mounts(struct sbuf *sb)
 
   // Every mount is in the table, /dev included. A fixed devtmpfs line here
   // listed it twice once init mounted it the ordinary way.
-  for (int i = 0; i < 16; i++) {
+  for (int i = 0; i < 32; i++) {
     if (mount_get(i, path, source, type, &fsdev) != 0)
       continue;
     // "/" is emitted last, below, so skip it if it somehow appears here.

kernel/fs/fs.c

@@ -1584,7 +1584,7 @@ skipelem(char *path, char *name, int *toolong)
 // a subtree becomes a place you can walk into and never out of.
 // ===========================================================================
 
-#define NMOUNT 8
+#define NMOUNT 32
 
 static struct {
   struct spinlock lock;