Add support for MS-DOS filesystems > 128 GB, by changing the way we

calculate fileids (fake inode numbers).  This uses some hash code by
Thomas Wang, who has agreed to the existing licence on the file (i.e.
his name just needed to be added to the copyright list).  Thanks.

Also a tiny bit of KNF.

Closes PR 4119; works for the OP Pawel Rogocz.

Help with testing todd@, thanks.

ok deraadt@

1 files changed, 103 insertions, 41 deletions

diff --git a/sys/msdosfs/msdosfs_vnops.c b/sys/msdosfs/msdosfs_vnops.c
index a05abf62425..cfb3720d189 100644
--- a/sys/msdosfs/msdosfs_vnops.c
+++ b/sys/msdosfs/msdosfs_vnops.c
@@ -1,7 +1,8 @@
-/*	$OpenBSD: msdosfs_vnops.c,v 1.51 2005/03/01 14:29:01 tom Exp $	*/
+/*	$OpenBSD: msdosfs_vnops.c,v 1.52 2005/03/02 00:44:12 tom Exp $	*/
 /*	$NetBSD: msdosfs_vnops.c,v 1.63 1997/10/17 11:24:19 ws Exp $	*/
 
 /*-
+ * Copyright (C) 2005 Thomas Wang.
  * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
  * Copyright (C) 1994, 1995, 1997 TooLs GmbH.
  * All rights reserved.
@@ -75,6 +76,8 @@
 #include <msdosfs/msdosfsmount.h>
 #include <msdosfs/fat.h>
 
+static uint32_t fileidhash(uint64_t);
+
 /*
  * Some general notes:
  *
@@ -265,27 +268,63 @@ msdosfs_getattr(v)
 	struct msdosfsmount *pmp = dep->de_pmp;
 	struct vattr *vap = ap->a_vap;
 	struct timespec ts;
-	uint32_t dirsperblk = pmp->pm_BytesPerSec / sizeof(struct direntry);
 	uint32_t fileid;
 
 	getnanotime(&ts);
 	DETIMES(dep, &ts, &ts, &ts);
 	vap->va_fsid = dep->de_dev;
+
 	/*
-	 * The following computation of the fileid must be the same as that
-	 * used in msdosfs_readdir() to compute d_fileno. If not, pwd
-	 * doesn't work.
+	 * The following computation of the fileid must be the same as
+	 * that used in msdosfs_readdir() to compute d_fileno. If not,
+	 * pwd doesn't work.
+	 *
+	 * We now use the starting cluster number as the fileid/fileno.
+	 * This works for both files and directories (including the root
+	 * directory, on FAT32).  Even on FAT32, this will at most be a
+	 * 28-bit number, as the high 4 bits of FAT32 cluster numbers
+	 * are reserved.
+	 *
+	 * However, we do need to do something for 0-length files, which
+	 * will not have a starting cluster number.
+	 *
+	 * These files cannot be directories, since (except for /, which
+	 * is special-cased anyway) directories contain entries for . and
+	 * .., so must have non-zero length.
+	 *
+	 * In this case, we just create a non-cryptographic hash of the
+	 * original fileid calculation, and set the top bit.
+	 *
+	 * This algorithm has the benefit that all directories, and all
+	 * non-zero-length files, will have fileids that are persistent
+	 * across mounts and reboots, and that cannot collide (as long
+	 * as the filesystem is not corrupt).  Zero-length files will
+	 * have fileids that are persistent, but that may collide.  We
+	 * will just have to live with that.
 	 */
+	fileid = dep->de_StartCluster;
+
 	if (dep->de_Attributes & ATTR_DIRECTORY) {
-	        fileid = cntobn(pmp, dep->de_StartCluster) * dirsperblk;
+		/* Special-case root */
 		if (dep->de_StartCluster == MSDOSFSROOT)
-		        fileid = 1;
+			fileid = FAT32(pmp) ? pmp->pm_rootdirblk : 1;
 	} else {
-	        fileid = cntobn(pmp, dep->de_dirclust) * dirsperblk;
-		if (dep->de_dirclust == MSDOSFSROOT)
-		        fileid = roottobn(pmp, 0) * dirsperblk;
-		fileid += dep->de_diroffset / sizeof(struct direntry);
+		if (dep->de_FileSize == 0) {
+			uint32_t dirsperblk;
+			uint64_t fileid64;
+
+			dirsperblk = pmp->pm_BytesPerSec /
+			    sizeof(struct direntry);
+
+			fileid64 = (dep->de_dirclust == MSDOSFSROOT) ?
+			    roottobn(pmp, 0) : cntobn(pmp, dep->de_dirclust);
+			fileid64 *= dirsperblk;
+			fileid64 += dep->de_diroffset / sizeof(struct direntry);
+
+			fileid = fileidhash(fileid64);
+		}
 	}
+
 	vap->va_fileid = fileid;
 	vap->va_mode = (S_IXUSR|S_IXGRP|S_IXOTH) | (S_IRUSR|S_IRGRP|S_IROTH) |
 	    ((dep->de_Attributes & ATTR_READONLY) ? 0 : (S_IWUSR|S_IWGRP|S_IWOTH));
@@ -926,7 +965,7 @@ abortit:
 	 * If source and dest are the same, do nothing.
 	 */
 	if (tvp == fvp) {
-	        error = 0;
+		error = 0;
 		goto abortit;
 	}
 
@@ -1271,7 +1310,7 @@ msdosfs_mkdir(v)
 	putushort(denp[0].deMTime, ndirent.de_MTime);
 	pcl = pdep->de_StartCluster;
 	if (FAT32(pmp) && pcl == pmp->pm_rootdirblk)
-	        pcl = 0;
+		pcl = 0;
 	putushort(denp[1].deStartCluster, pcl);
 	putushort(denp[1].deCDate, ndirent.de_CDate);
 	putushort(denp[1].deCTime, ndirent.de_CTime);
@@ -1280,7 +1319,7 @@ msdosfs_mkdir(v)
 	putushort(denp[1].deMDate, ndirent.de_MDate);
 	putushort(denp[1].deMTime, ndirent.de_MTime);
 	if (FAT32(pmp)) {
-	        putushort(denp[0].deHighClust, newcluster >> 16);
+		putushort(denp[0].deHighClust, newcluster >> 16);
 		putushort(denp[1].deHighClust, pdep->de_StartCluster >> 16);
 	}
 
@@ -1502,9 +1541,7 @@ msdosfs_readdir(v)
 			for (n = (int)offset / sizeof(struct direntry);
 			     n < 2; n++) {
 			        if (FAT32(pmp))
-				        dirbuf.d_fileno = cntobn(pmp,
-								 pmp->pm_rootdirblk)
-					                  * dirsperblk;
+				        dirbuf.d_fileno = pmp->pm_rootdirblk;
 				else
 				        dirbuf.d_fileno = 1;
 				dirbuf.d_type = DT_DIR;
@@ -1597,41 +1634,43 @@ msdosfs_readdir(v)
 				chksum = -1;
 				continue;
 			}
+
 			/*
 			 * This computation of d_fileno must match
 			 * the computation of va_fileid in
 			 * msdosfs_getattr.
 			 */
+			fileno = getushort(dentp->deStartCluster);
+			if (FAT32(pmp))
+			    fileno |= getushort(dentp->deHighClust) << 16;
+
 			if (dentp->deAttributes & ATTR_DIRECTORY) {
-				fileno = getushort(dentp->deStartCluster);
-				if (FAT32(pmp))
-				        fileno |=
-					    getushort(dentp->deHighClust) <<
-					    16;
-				/* if this is the root directory */
-				if (fileno == MSDOSFSROOT)
-				        fileno = FAT32(pmp) ?
-					    cntobn(pmp, pmp->pm_rootdirblk) *
-					    dirsperblk :
-					    1;
-				else
-				        fileno = cntobn(pmp, fileno) *
-					    dirsperblk;
+				/* Special-case root */
+				if (fileno == MSDOSFSROOT)  {
+					fileno = FAT32(pmp) ?
+					    pmp->pm_rootdirblk : 1;
+				}
+
 				dirbuf.d_fileno = fileno;
 				dirbuf.d_type = DT_DIR;
 			} else {
-				/*
-				 * If the file's dirent lives in
-				 * root dir.
-				 */
-			        fileno = cntobn(pmp, cn) * dirsperblk;
-				if (cn == MSDOSFSROOT)
-				        fileno = roottobn(pmp, 0) * dirsperblk;
-				fileno +=
-				    dentp - (struct direntry *)bp->b_data;
+				if (getulong(dentp->deFileSize) == 0) {
+					uint64_t fileno64;
+
+					fileno64 = (cn == MSDOSFSROOT) ?
+					    roottobn(pmp, 0) : cntobn(pmp, cn);
+
+					fileno64 *= dirsperblk;
+					fileno64 += dentp -
+					    (struct direntry *)bp->b_data;
+
+					fileno = fileidhash(fileno64);
+				}
+
 				dirbuf.d_fileno = fileno;
 				dirbuf.d_type = DT_REG;
 			}
+
 			if (chksum != winChksum(dentp->deName))
 				dirbuf.d_namlen = dos2unixfn(dentp->deName,
 				    (u_char *)dirbuf.d_name,
@@ -1702,7 +1741,7 @@ msdosfs_lock(v)
 		int a_flags;
 		struct proc *a_p;
 	} */ *ap = v;
-        struct vnode *vp = ap->a_vp;
+	struct vnode *vp = ap->a_vp;
 
 	return (lockmgr(&VTODE(vp)->de_lock, ap->a_flags, &vp->v_interlock,
 	    ap->a_p));
@@ -1900,6 +1939,29 @@ msdosfs_pathconf(v)
 	/* NOTREACHED */
 }
 
+/*
+ * Thomas Wang's hash function, severely hacked to always set the high
+ * bit on the number it returns (so no longer a proper hash function).
+ */
+static uint32_t
+fileidhash(uint64_t fileid)
+{
+	uint64_t c1 = 0x6e5ea73858134343LL;
+	uint64_t c2 = 0xb34e8f99a2ec9ef5LL;
+
+	/*
+	 * We now have the original fileid value, as 64-bit value.
+	 * We need to reduce it to 32-bits, with the toe bit set.
+	 */
+	fileid ^= ((c1 ^ fileid) >> 32);
+	fileid *= c1;
+	fileid ^= ((c2 ^ fileid) >> 31);
+	fileid *= c2;
+	fileid ^= ((c1 ^ fileid) >> 32);
+
+	return (uint32_t)(fileid | 0x80000000);
+}
+
 /* Global vfs data structures for msdosfs */
 int (**msdosfs_vnodeop_p)(void *);
 struct vnodeopv_entry_desc msdosfs_vnodeop_entries[] = {