Date: Fri, 24 Dec 1999 01:50:02 -0800 (PST) From: Boris Popov <bp@butya.kz> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/15136: Panic on MSDOS FS mount Message-ID: <199912240950.BAA88522@freefall.freebsd.org>
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The following reply was made to PR kern/15136; it has been noted by GNATS.
From: Boris Popov <bp@butya.kz>
To: freebsd-gnats-submit@freebsd.org, netch@lucky.net
Cc:
Subject: Re: kern/15136: Panic on MSDOS FS mount
Date: Fri, 24 Dec 1999 15:41:23 +0600
> On attempt to mount MSDOS (FAT16) file system, kernel falls to panic with
> message:
> panic: vm_fault: fault on nofault entry, addr=c16de000
This caused by inconsistent data in the boot record. Could please test
the following patch and tell me if this helps:
diff -u ../msdosfs_vfsops.c ./msdosfs_vfsops.c
--- ../msdosfs_vfsops.c Sun Dec 19 12:07:56 1999
+++ ./msdosfs_vfsops.c Fri Dec 24 15:15:08 1999
@@ -364,6 +364,7 @@
struct byte_bpb50 *b50;
struct byte_bpb710 *b710;
u_int8_t SecPerClust;
+ u_long clusters;
int ronly, error;
/*
@@ -595,14 +596,13 @@
pmp->pm_firstcluster = pmp->pm_rootdirblk +
pmp->pm_rootdirsize;
}
- pmp->pm_nmbrofclusters = (pmp->pm_HugeSectors - pmp->pm_firstcluster)
/
- SecPerClust;
- pmp->pm_maxcluster = pmp->pm_nmbrofclusters + 1;
+ pmp->pm_maxcluster = (pmp->pm_HugeSectors - pmp->pm_firstcluster) /
+ SecPerClust + 1;
pmp->pm_fatsize = pmp->pm_FATsecs * pmp->pm_BytesPerSec;
#ifndef __FreeBSD__
if (argp->flags & MSDOSFSMNT_GEMDOSFS) {
- if ((pmp->pm_nmbrofclusters <= (0xff0 - 2))
+ if ((pmp->pm_maxcluster <= (0xff0 - 2))
&& ((dtype == DTYPE_FLOPPY) || ((dtype == DTYPE_VNODE)
&& ((pmp->pm_Heads == 1) || (pmp->pm_Heads == 2))))
) {
@@ -633,6 +633,15 @@
pmp->pm_fatdiv = 1;
}
}
+
+ clusters = (pmp->pm_fatsize / pmp->pm_fatmult) * pmp->pm_fatdiv;
+ if (pmp->pm_maxcluster >= clusters) {
+ printf("Warning: number of clusters (%ld) exceeds FAT "
+ "capasity (%ld)\n", pmp->pm_maxcluster + 1, clusters);
+ pmp->pm_maxcluster = clusters - 1;
+ }
+
+
if (FAT12(pmp))
pmp->pm_fatblocksize = 3 * pmp->pm_BytesPerSec;
else
@@ -829,7 +838,7 @@
pmp = VFSTOMSDOSFS(mp);
sbp->f_bsize = pmp->pm_bpcluster;
sbp->f_iosize = pmp->pm_bpcluster;
- sbp->f_blocks = pmp->pm_nmbrofclusters;
+ sbp->f_blocks = pmp->pm_maxcluster + 1;
sbp->f_bfree = pmp->pm_freeclustercount;
sbp->f_bavail = pmp->pm_freeclustercount;
sbp->f_files = pmp->pm_RootDirEnts; /* XXX */
diff -u ../msdosfsmount.h ./msdosfsmount.h
--- ../msdosfsmount.h Sat Aug 28 07:48:11 1999
+++ ./msdosfsmount.h Fri Dec 24 12:18:12 1999
@@ -73,7 +73,6 @@
u_long pm_rootdirblk; /* block # (cluster # for FAT32) of root
directory number */
u_long pm_rootdirsize; /* size in blocks (not clusters) */
u_long pm_firstcluster; /* block number of first cluster */
- u_long pm_nmbrofclusters; /* # of clusters in filesystem */
u_long pm_maxcluster; /* maximum cluster number */
u_long pm_freeclustercount; /* number of free clusters */
u_long pm_cnshift; /* shift file offset right this amount to get
a cluster number */
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