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kernel-49/Documentation/filesystems/affs.txt
Greg Kroah-Hartman 6e3051fb4d Merge 4.9.236 into android-4.9-q 
Changes in 4.9.236
	HID: core: Correctly handle ReportSize being zero
	HID: core: Sanitize event code and type when mapping input
	perf record/stat: Explicitly call out event modifiers in the documentation
	hwmon: (applesmc) check status earlier.
	nvmet: Disable keep-alive timer when kato is cleared to 0h
	ceph: don't allow setlease on cephfs
	s390: don't trace preemption in percpu macros
	xen/xenbus: Fix granting of vmalloc'd memory
	dmaengine: of-dma: Fix of_dma_router_xlate's of_dma_xlate handling
	batman-adv: Avoid uninitialized chaddr when handling DHCP
	batman-adv: bla: use netif_rx_ni when not in interrupt context
	dmaengine: at_hdmac: check return value of of_find_device_by_node() in at_dma_xlate()
	MIPS: mm: BMIPS5000 has inclusive physical caches
	MIPS: BMIPS: Also call bmips_cpu_setup() for secondary cores
	netfilter: nf_tables: add NFTA_SET_USERDATA if not null
	netfilter: nf_tables: incorrect enum nft_list_attributes definition
	netfilter: nf_tables: fix destination register zeroing
	net: hns: Fix memleak in hns_nic_dev_probe
	ravb: Fixed to be able to unload modules
	net: arc_emac: Fix memleak in arc_mdio_probe
	dmaengine: pl330: Fix burst length if burst size is smaller than bus width
	bnxt_en: Check for zero dir entries in NVRAM.
	bnxt_en: Fix PCI AER error recovery flow
	fix regression in "epoll: Keep a reference on files added to the check list"
	tg3: Fix soft lockup when tg3_reset_task() fails.
	iommu/vt-d: Serialize IOMMU GCMD register modifications
	thermal: ti-soc-thermal: Fix bogus thermal shutdowns for omap4430
	include/linux/log2.h: add missing () around n in roundup_pow_of_two()
	btrfs: drop path before adding new uuid tree entry
	btrfs: Remove redundant extent_buffer_get in get_old_root
	btrfs: Remove extraneous extent_buffer_get from tree_mod_log_rewind
	btrfs: set the lockdep class for log tree extent buffers
	uaccess: Add non-pagefault user-space read functions
	uaccess: Add non-pagefault user-space write function
	btrfs: fix potential deadlock in the search ioctl
	net: usb: qmi_wwan: add Telit 0x1050 composition
	drivers: net: usb: qmi_wwan: add QMI_QUIRK_SET_DTR for Telit PID 0x1201
	qmi_wwan: new Telewell and Sierra device IDs
	usb: qmi_wwan: add D-Link DWM-222 A2 device ID
	ALSA: ca0106: fix error code handling
	ALSA: pcm: oss: Remove superfluous WARN_ON() for mulaw sanity check
	ALSA: firewire-digi00x: exclude Avid Adrenaline from detection
	block: allow for_each_bvec to support zero len bvec
	block: Move SECTOR_SIZE and SECTOR_SHIFT definitions into <linux/blkdev.h>
	libata: implement ATA_HORKAGE_MAX_TRIM_128M and apply to Sandisks
	dm cache metadata: Avoid returning cmd->bm wild pointer on error
	dm thin metadata: Avoid returning cmd->bm wild pointer on error
	mm: slub: fix conversion of freelist_corrupted()
	vfio/type1: Support faulting PFNMAP vmas
	vfio-pci: Fault mmaps to enable vma tracking
	vfio-pci: Invalidate mmaps and block MMIO access on disabled memory
	KVM: arm64: Add kvm_extable for vaxorcism code
	KVM: arm64: Defer guest entry when an asynchronous exception is pending
	KVM: arm64: Survive synchronous exceptions caused by AT instructions
	KVM: arm64: Set HCR_EL2.PTW to prevent AT taking synchronous exception
	net: refactor bind_bucket fastreuse into helper
	net: initialize fastreuse on inet_inherit_port
	vfio/pci: Fix SR-IOV VF handling with MMIO blocking
	checkpatch: fix the usage of capture group ( ... )
	mm/hugetlb: fix a race between hugetlb sysctl handlers
	cfg80211: regulatory: reject invalid hints
	net: usb: Fix uninit-was-stored issue in asix_read_phy_addr()
	ALSA; firewire-tascam: exclude Tascam FE-8 from detection
	fs/affs: use octal for permissions
	affs: fix basic permission bits to actually work
	net: ethernet: mlx4: Fix memory allocation in mlx4_buddy_init()
	bnxt: don't enable NAPI until rings are ready
	netlabel: fix problems with mapping removal
	sctp: not disable bh in the whole sctp_get_port_local()
	net: disable netpoll on fresh napis
	Linux 4.9.236

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I707909fadc45a09f6ecdacb81a294421af163664
2020-09-12 21:03:26 +03:00

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Overview of Amiga Filesystems
=============================
Not all varieties of the Amiga filesystems are supported for reading and
writing. The Amiga currently knows six different filesystems:
DOS\0 The old or original filesystem, not really suited for
hard disks and normally not used on them, either.
Supported read/write.
DOS\1 The original Fast File System. Supported read/write.
DOS\2 The old "international" filesystem. International means that
a bug has been fixed so that accented ("international") letters
in file names are case-insensitive, as they ought to be.
Supported read/write.
DOS\3 The "international" Fast File System. Supported read/write.
DOS\4 The original filesystem with directory cache. The directory
cache speeds up directory accesses on floppies considerably,
but slows down file creation/deletion. Doesn't make much
sense on hard disks. Supported read only.
DOS\5 The Fast File System with directory cache. Supported read only.
All of the above filesystems allow block sizes from 512 to 32K bytes.
Supported block sizes are: 512, 1024, 2048 and 4096 bytes. Larger blocks
speed up almost everything at the expense of wasted disk space. The speed
gain above 4K seems not really worth the price, so you don't lose too
much here, either.
The muFS (multi user File System) equivalents of the above file systems
are supported, too.
Mount options for the AFFS
==========================
protect If this option is set, the protection bits cannot be altered.
setuid[=uid] This sets the owner of all files and directories in the file
system to uid or the uid of the current user, respectively.
setgid[=gid] Same as above, but for gid.
mode=mode Sets the mode flags to the given (octal) value, regardless
of the original permissions. Directories will get an x
permission if the corresponding r bit is set.
This is useful since most of the plain AmigaOS files
will map to 600.
nofilenametruncate
The file system will return an error when filename exceeds
standard maximum filename length (30 characters).
reserved=num Sets the number of reserved blocks at the start of the
partition to num. You should never need this option.
Default is 2.
root=block Sets the block number of the root block. This should never
be necessary.
bs=blksize Sets the blocksize to blksize. Valid block sizes are 512,
1024, 2048 and 4096. Like the root option, this should
never be necessary, as the affs can figure it out itself.
quiet The file system will not return an error for disallowed
mode changes.
verbose The volume name, file system type and block size will
be written to the syslog when the filesystem is mounted.
mufs The filesystem is really a muFS, also it doesn't
identify itself as one. This option is necessary if
the filesystem wasn't formatted as muFS, but is used
as one.
prefix=path Path will be prefixed to every absolute path name of
symbolic links on an AFFS partition. Default = "/".
(See below.)
volume=name When symbolic links with an absolute path are created
on an AFFS partition, name will be prepended as the
volume name. Default = "" (empty string).
(See below.)
Handling of the Users/Groups and protection flags
=================================================
Amiga -> Linux:
The Amiga protection flags RWEDRWEDHSPARWED are handled as follows:
- R maps to r for user, group and others. On directories, R implies x.
- W maps to w.
- E maps to x.
- D is ignored.
- H, S and P are always retained and ignored under Linux.
- A is cleared when a file is written to.
User id and group id will be used unless set[gu]id are given as mount
options. Since most of the Amiga file systems are single user systems
they will be owned by root. The root directory (the mount point) of the
Amiga filesystem will be owned by the user who actually mounts the
filesystem (the root directory doesn't have uid/gid fields).
Linux -> Amiga:
The Linux rwxrwxrwx file mode is handled as follows:
- r permission will allow R for user, group and others.
- w permission will allow W for user, group and others.
- x permission of the user will allow E for plain files.
- D will be allowed for user, group and others.
- All other flags (suid, sgid, ...) are ignored and will
not be retained.
Newly created files and directories will get the user and group ID
of the current user and a mode according to the umask.
Symbolic links
==============
Although the Amiga and Linux file systems resemble each other, there
are some, not always subtle, differences. One of them becomes apparent
with symbolic links. While Linux has a file system with exactly one
root directory, the Amiga has a separate root directory for each
file system (for example, partition, floppy disk, ...). With the Amiga,
these entities are called "volumes". They have symbolic names which
can be used to access them. Thus, symbolic links can point to a
different volume. AFFS turns the volume name into a directory name
and prepends the prefix path (see prefix option) to it.
Example:
You mount all your Amiga partitions under /amiga/<volume> (where
<volume> is the name of the volume), and you give the option
"prefix=/amiga/" when mounting all your AFFS partitions. (They
might be "User", "WB" and "Graphics", the mount points /amiga/User,
/amiga/WB and /amiga/Graphics). A symbolic link referring to
"User:sc/include/dos/dos.h" will be followed to
"/amiga/User/sc/include/dos/dos.h".
Examples
========
Command line:
mount Archive/Amiga/Workbench3.1.adf /mnt -t affs -o loop,verbose
mount /dev/sda3 /Amiga -t affs
/etc/fstab entry:
/dev/sdb5 /amiga/Workbench affs noauto,user,exec,verbose 0 0
IMPORTANT NOTE
==============
If you boot Windows 95 (don't know about 3.x, 98 and NT) while you
have an Amiga harddisk connected to your PC, it will overwrite
the bytes 0x00dc..0x00df of block 0 with garbage, thus invalidating
the Rigid Disk Block. Sheer luck has it that this is an unused
area of the RDB, so only the checksum doesn't match anymore.
Linux will ignore this garbage and recognize the RDB anyway, but
before you connect that drive to your Amiga again, you must
restore or repair your RDB. So please do make a backup copy of it
before booting Windows!
If the damage is already done, the following should fix the RDB
(where <disk> is the device name).
DO AT YOUR OWN RISK:
dd if=/dev/<disk> of=rdb.tmp count=1
cp rdb.tmp rdb.fixed
dd if=/dev/zero of=rdb.fixed bs=1 seek=220 count=4
dd if=rdb.fixed of=/dev/<disk>
Bugs, Restrictions, Caveats
===========================
Quite a few things may not work as advertised. Not everything is
tested, though several hundred MB have been read and written using
this fs. For a most up-to-date list of bugs please consult
fs/affs/Changes.
By default, filenames are truncated to 30 characters without warning.
'nofilenametruncate' mount option can change that behavior.
Case is ignored by the affs in filename matching, but Linux shells
do care about the case. Example (with /wb being an affs mounted fs):
rm /wb/WRONGCASE
will remove /mnt/wrongcase, but
rm /wb/WR*
will not since the names are matched by the shell.
The block allocation is designed for hard disk partitions. If more
than 1 process writes to a (small) diskette, the blocks are allocated
in an ugly way (but the real AFFS doesn't do much better). This
is also true when space gets tight.
You cannot execute programs on an OFS (Old File System), since the
program files cannot be memory mapped due to the 488 byte blocks.
For the same reason you cannot mount an image on such a filesystem
via the loopback device.
The bitmap valid flag in the root block may not be accurate when the
system crashes while an affs partition is mounted. There's currently
no way to fix a garbled filesystem without an Amiga (disk validator)
or manually (who would do this?). Maybe later.
If you mount affs partitions on system startup, you may want to tell
fsck that the fs should not be checked (place a '0' in the sixth field
of /etc/fstab).
It's not possible to read floppy disks with a normal PC or workstation
due to an incompatibility with the Amiga floppy controller.
If you are interested in an Amiga Emulator for Linux, look at
http://web.archive.org/web/*/http://www.freiburg.linux.de/~uae/
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