linux-toradex.git/drivers/block/nbd.c, branch v3.10.2

nbd: correct disconnect behavior

2013-07-22T01:21:29+00:00

commit c378f70adbc1bbecd9e6db145019f14b2f688c7c upstream.

Currently, when a disconnect is requested by the user (via NBD_DISCONNECT
ioctl) the return from NBD_DO_IT is undefined (it is usually one of
several error codes).  This means that nbd-client does not know if a
manual disconnect was performed or whether a network error occurred.
Because of this, nbd-client's persist mode (which tries to reconnect after
error, but not after manual disconnect) does not always work correctly.

This change fixes this by causing NBD_DO_IT to always return 0 if a user
requests a disconnect.  This means that nbd-client can correctly either
persist the connection (if an error occurred) or disconnect (if the user
requested it).

Signed-off-by: Paul Clements 
Acked-by: Rob Landley 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

block: do not pass disk names as format strings

2013-07-13T18:42:26+00:00

commit ffc8b30866879ed9ba62bd0a86fecdbd51cd3d19 upstream.

Disk names may contain arbitrary strings, so they must not be
interpreted as format strings.  It seems that only md allows arbitrary
strings to be used for disk names, but this could allow for a local
memory corruption from uid 0 into ring 0.

CVE-2013-2851

Signed-off-by: Kees Cook 
Cc: Jens Axboe 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

nbd: increase default and max request sizes

2013-05-01T00:04:07+00:00

Raise the default max request size for nbd to 128KB (from 127KB) to get it
4KB aligned.  This patch also allows the max request size to be increased
(via /sys/block/nbd/queue/max_sectors_kb) to 32MB.

The patch makes nbd network traffic more efficient by:
- reducing request fragmentation (4KB alignment)
- reducing the number of requests (fewer round trips, less network overhead)

Especially in high latency networks, larger request size can make a dramatic

Signed-off-by: Paul Clements 
Signed-off-by: Michal Belczyk 
Cc: Jens Axboe 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

nbd: fix sparse warning

2013-02-28T03:10:22+00:00

I just fixed this in "drivers/block/rbd.c" and I noticed that
"drivers/block/nbd.c" has the same problem.  Fix a warning issued by
sparse by adding some lockdep annotations to indicate the queue lock gets
dropped (because it's held when do_nbd_request() is called) and
re-acquired within the function.

Signed-off-by: Alex Elder 
Cc: Paul Clements 
Cc: Paul Clements 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

nbd: show read-only state in sysfs

2013-02-28T03:10:22+00:00

Pass the read-only flag to set_device_ro, so that it will be visible to
the block layer and in sysfs.

Signed-off-by: Paolo Bonzini 
Cc: Paul Clements 
Cc: Alex Bligh 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

nbd: fsync and kill block device on shutdown

2013-02-28T03:10:22+00:00

There are two problems with shutdown in the NBD driver.

1: Receiving the NBD_DISCONNECT ioctl does not sync the filesystem.

   This patch adds the sync operation into __nbd_ioctl()'s
   NBD_DISCONNECT handler.  This is useful because BLKFLSBUF is restricted
   to processes that have CAP_SYS_ADMIN, and the NBD client may not
   possess it (fsync of the block device does not sync the filesystem,
   either).

2: Once we clear the socket we have no guarantee that later reads will
   come from the same backing storage.

   The patch adds calls to kill_bdev() in __nbd_ioctl()'s socket
   clearing code so the page cache is cleaned, lest reads that hit on the
   page cache will return stale data from the previously-accessible disk.

Example:

    # qemu-nbd -r -c/dev/nbd0 /dev/sr0
    # file -s /dev/nbd0
    /dev/stdin: # UDF filesystem data (version 1.5) etc.
    # qemu-nbd -d /dev/nbd0
    # qemu-nbd -r -c/dev/nbd0 /dev/sda
    # file -s /dev/nbd0
    /dev/stdin: # UDF filesystem data (version 1.5) etc.

While /dev/sda has:

    # file -s /dev/sda
    /dev/sda: x86 boot sector; etc.

Signed-off-by: Paolo Bonzini 
Acked-by: Paul Clements 
Cc: Alex Bligh 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

nbd: support FLUSH requests

2013-02-28T03:10:22+00:00

Currently, the NBD device does not accept flush requests from the Linux
block layer.  If the NBD server opened the target with neither O_SYNC nor
O_DSYNC, however, the device will be effectively backed by a writeback
cache.  Without issuing flushes properly, operation of the NBD device will
not be safe against power losses.

The NBD protocol has support for both a cache flush command and a FUA
command flag; the server will also pass a flag to note its support for
these features.  This patch adds support for the cache flush command and
flag.  In the kernel, we receive the flags via the NBD_SET_FLAGS ioctl,
and map NBD_FLAG_SEND_FLUSH to the argument of blk_queue_flush.  When the
flag is active the block layer will send REQ_FLUSH requests, which we
translate to NBD_CMD_FLUSH commands.

FUA support is not included in this patch because all free software
servers implement it with a full fdatasync; thus it has no advantage over
supporting flush only.  Because I [Paolo] cannot really benchmark it in a
realistic scenario, I cannot tell if it is a good idea or not.  It is also
not clear if it is valid for an NBD server to support FUA but not flush.
The Linux block layer gives a warning for this combination, the NBD
protocol documentation says nothing about it.

The patch also fixes a small problem in the handling of flags: nbd->flags
must be cleared at the end of NBD_DO_IT, but the driver was not doing
that.  The bug manifests itself as follows.  Suppose you two different
client/server pairs to start the NBD device.  Suppose also that the first
client supports NBD_SET_FLAGS, and the first server sends
NBD_FLAG_SEND_FLUSH; the second pair instead does neither of these two
things.  Before this patch, the second invocation of NBD_DO_IT will use a
stale value of nbd->flags, and the second server will issue an error every
time it receives an NBD_CMD_FLUSH command.

This bug is pre-existing, but it becomes much more important after this
patch; flush failures make the device pretty much unusable, unlike

Signed-off-by: Paolo Bonzini 
Signed-off-by: Alex Bligh 
Acked-by: Paul Clements 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

new helper: file_inode(file)

2013-02-23T04:31:31+00:00

Signed-off-by: Al Viro

nbd: handle discard requests

2012-10-05T18:05:24+00:00

Add discard support to nbd.  If the nbd-server supports discard, it will
send NBD_FLAG_SEND_TRIM to the client.  The client will then set the flag
in the kernel via NBD_SET_FLAGS, which tells the kernel to enable discards
for the device (QUEUE_FLAG_DISCARD).

If discard support is enabled, then when the nbd client system receives a
discard request, this will be passed along to the nbd-server.  When the
discard request is received by the nbd-server, it will perform:

	fallocate(.. FALLOC_FL_PUNCH_HOLE ..)

To punch a hole in the backend storage, which is no longer needed.

Signed-off-by: Paul Clements 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

nbd: add set flags ioctl

2012-10-05T18:05:23+00:00

Add a set-flags ioctl, allowing various option flags to be set on an nbd
device.  This allows the nbd-client to set the device flags (to enable
read-only mode, or enable discard support, etc.).

Flags are typically specified by the nbd-server.  During the negotiation
phase of the nbd connection, the server sends its flags to the client.
The client then uses NBD_SET_FLAGS to inform the kernel of the options.

Also included is a one-line fix to debug output for the set-timeout ioctl.

Signed-off-by: Paul Clements 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds