Messages in this thread |  | | From | (H. Peter Anvin) | Subject | Serious fat + ramdisk/loopback bug | Date | 13 Jun 1996 22:25:06 GMT |
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There seems to be a bad interaction between the FAT filesystem driver and the ramdisk/loopback drivers. This presumably indicates a buffer cache problem, possible something having to do with the new buffer cache code?
Anyway:
--- With ramdisk ---
trantor 206 # uname -a Linux trantor 2.0.0 #3 Sun Jun 9 11:27:43 PDT 1996 i586 trantor 207 # cat test.img > /dev/ram0 trantor 208 # dd if=/dev/ram0 bs=64 count=1 | mydump 1+0 records in 1+0 records out 00000000: EB 3C 90 27 66 2E 5B 43-49 48 43 00 02 01 01 00 ë<.'f.[CIHC..... 00000010: 02 E0 00 40 0B F0 09 00-12 00 02 00 00 00 00 00 .à.@.ð.......... 00000020: 00 00 00 00 00 00 29 D9-16 26 37 4E 4F 20 4E 41 ......)Ù.&7NO NA 00000030: 4D 45 20 20 20 20 46 41-54 31 32 20 20 20 FA 33 ME FAT12 ú3
trantor 209 # mount -r -t msdos /dev/ram0 /mnt mount: wrong fs type, bad option, bad superblock on /dev/ram0, or too many mounted file systems trantor 210 # dd if=/dev/ram0 bs=64 count=1 | mydump 1+0 records in 1+0 records out 00000000: 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................ 00000010: 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................ 00000020: 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................ 00000030: 00 00 00 00 00 00 00 00-00 00 00 00 00 00 00 00 ................
--- With loopback device (mount-2.5j) ---
[Note: file test.img is an image of the floppy in /dev/fd0]
trantor 211 # trantor 211 # mount -r -t msdos -o loop test.img /mnt trantor 212 # ls -l /mnt
<Sound FX: intense seek activity on the hard disk>
total 0 trantor 213 # dd if=/dev/loop0 bs=64 count=1 | mydump 1+0 records in 1+0 records out 00000000: EB 3C 90 27 66 2E 5B 43-49 48 43 00 02 01 01 00 ë<.'f.[CIHC..... 00000010: 02 E0 00 40 0B F0 09 00-12 00 02 00 00 00 00 00 .à.@.ð.......... 00000020: 00 00 00 00 00 00 29 D9-16 26 37 4E 4F 20 4E 41 ......)Ù.&7NO NA 00000030: 4D 45 20 20 20 20 46 41-54 31 32 20 20 20 FA 33 ME FAT12 ú3
trantor 214 # mount -r -t msdos /dev/fd0 /mnt2 trantor 215 # ls -l /mnt2 total 68 drwxr-xr-x 2 root sys 512 Aug 23 1995 driver -rwxr-xr-x 1 root sys 42873 Aug 14 1995 fasetup.ex_ -rwxr-xr-x 1 root sys 6080 Aug 14 1995 fasmeter.dll -rwxr-xr-x 1 root sys 7410 Aug 14 1995 readme.txt drwxr-xr-x 2 root sys 1024 Aug 23 1995 scantool -rwxr-xr-x 1 root sys 6144 Aug 14 1995 setup.exe -rwxr-xr-x 1 root sys 3092 Aug 14 1995 setup.inf
trantor 222 # dd if=/dev/fd0 bs=18x512 count=160 | sum 160+0 records in 160+0 records out 39579 1440 trantor 223 # sum test.img 39579 1440
Repeating the exercise with an ext2 filesystem image works just fine.
This is a major problem to me, since I have a direct need of using either of these methods to create DOS filesystem images.
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