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authorConrad Meyer <cse.cem@gmail.com>2014-06-06 14:36:37 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-06 16:08:10 -0700
commit190a8843ded231638d0e7ae7d8ca6a712472d114 (patch)
tree30e99192bc39f30584197eab47b119478d8dfe37 /Documentation/filesystems/vfat.txt
parenta19189e5535ed8fd191d8989fc39da1637cfa224 (diff)
fs/fat/: add support for DOS 1.x formatted volumes
Add structure for parsed BPB information, struct fat_bios_param_block, and move all of the deserialization and validation logic from fat_fill_super() into fat_read_bpb(). Add a 'dos1xfloppy' mount option to infer DOS 2.x BIOS Parameter Block defaults from block device geometry for ancient floppies and floppy images, as a fall-back from the default BPB parsing logic. When fat_read_bpb() finds an invalid FAT filesystem and dos1xfloppy is set, fall back to fat_read_static_bpb(). fat_read_static_bpb() validates that the entire BPB is zero, and that the floppy has a DOS-style 8086 code bootstrapping header. Then it fills in default BPB values from media size and a table.[0] Media size is assumed to be static for archaic FAT volumes. See also: [1]. Fixes kernel.org bug #42617. [0]: https://en.wikipedia.org/wiki/File_Allocation_Table#Exceptions [1]: http://www.win.tue.nl/~aeb/linux/fs/fat/fat-1.html [hirofumi@mail.parknet.co.jp: fix missed error code] Signed-off-by: Conrad Meyer <cse.cem@gmail.com> Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Tested-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/filesystems/vfat.txt')
-rw-r--r--Documentation/filesystems/vfat.txt5
1 files changed, 5 insertions, 0 deletions
diff --git a/Documentation/filesystems/vfat.txt b/Documentation/filesystems/vfat.txt
index 4a93e98b290a..ce1126aceed8 100644
--- a/Documentation/filesystems/vfat.txt
+++ b/Documentation/filesystems/vfat.txt
@@ -172,6 +172,11 @@ nfs=stale_rw|nostale_ro
To maintain backward compatibility, '-o nfs' is also accepted,
defaulting to stale_rw
+dos1xfloppy -- If set, use a fallback default BIOS Parameter Block
+ configuration, determined by backing device size. These static
+ parameters match defaults assumed by DOS 1.x for 160 kiB,
+ 180 kiB, 320 kiB, and 360 kiB floppies and floppy images.
+
<bool>: 0,1,yes,no,true,false