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This allows userspace to completely setup a loop device with a single
ioctl, removing the in-between state where the device can be partially
configured - eg the loop device has a backing file associated with it,
but is reading from the wrong offset.
Besides removing the intermediate state, another big benefit of this
ioctl is that LOOP_SET_STATUS can be slow; the main reason for this
slowness is that LOOP_SET_STATUS(64) calls blk_mq_freeze_queue() to
freeze the associated queue; this requires waiting for RCU
synchronization, which I've measured can take about 15-20ms on this
device on average.
In addition to doing what LOOP_SET_STATUS can do, LOOP_CONFIGURE can
also be used to:
- Set the correct block size immediately by setting
loop_config.block_size (avoids LOOP_SET_BLOCK_SIZE)
- Explicitly request direct I/O mode by setting LO_FLAGS_DIRECT_IO
in loop_config.info.lo_flags (avoids LOOP_SET_DIRECT_IO)
- Explicitly request read-only mode by setting LO_FLAGS_READ_ONLY
in loop_config.info.lo_flags
Here's setting up ~70 regular loop devices with an offset on an x86
Android device, using LOOP_SET_FD and LOOP_SET_STATUS:
vsoc_x86:/system/apex # time for i in `seq 30 100`;
do losetup -r -o 4096 /dev/block/loop$i com.android.adbd.apex; done
0m03.40s real 0m00.02s user 0m00.03s system
Here's configuring ~70 devices in the same way, but using a modified
losetup that uses the new LOOP_CONFIGURE ioctl:
vsoc_x86:/system/apex # time for i in `seq 30 100`;
do losetup -r -o 4096 /dev/block/loop$i com.android.adbd.apex; done
0m01.94s real 0m00.01s user 0m00.01s system
Signed-off-by: Martijn Coenen <maco@android.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
(cherry picked from commit 3448914e8cc550ba792d4ccc74471d1ca4293aae)
Bug: 148607611
Change-Id: I839ee9c9df8dbd9f4cc0fa5c8119c01abfcac1d9
Martijn Coenen
commited |
9a7c579b77 | |
LOOP_SET_STATUS(64) will actually allow some lo_flags to be modified; in particular, LO_FLAGS_AUTOCLEAR can be set and cleared, whereas LO_FLAGS_PARTSCAN can be set to request a partition scan. Make this explicit by updating the UAPI to include the flags that can be set/cleared using this ioctl. The implementation can then blindly take over the passed in flags, and use the previous flags for those flags that can't be set / cleared using LOOP_SET_STATUS. Signed-off-by: Martijn Coenen <maco@android.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk> (cherry picked from commit faf1d25440d6ad06d509dada4b6fe62fea844370) Bug: 148607611 Change-Id: If80c0cce4ef7b1af4753246021981795bbc54ca0
Martijn Coenen
commited |
a7bbde7dfb | |
Many user space API headers have licensing information, which is either
incomplete, badly formatted or just a shorthand for referring to the
license under which the file is supposed to be. This makes it hard for
compliance tools to determine the correct license.
Update these files with an SPDX license identifier. The identifier was
chosen based on the license information in the file.
GPL/LGPL licensed headers get the matching GPL/LGPL SPDX license
identifier with the added 'WITH Linux-syscall-note' exception, which is
the officially assigned exception identifier for the kernel syscall
exception:
NOTE! This copyright does *not* cover user programs that use kernel
services by normal system calls - this is merely considered normal use
of the kernel, and does *not* fall under the heading of "derived work".
This exception makes it possible to include GPL headers into non GPL
code, without confusing license compliance tools.
Headers which have either explicit dual licensing or are just licensed
under a non GPL license are updated with the corresponding SPDX
identifier and the GPLv2 with syscall exception identifier. The format
is:
((GPL-2.0 WITH Linux-syscall-note) OR SPDX-ID-OF-OTHER-LICENSE)
SPDX license identifiers are a legally binding shorthand, which can be
used instead of the full boiler plate text. The update does not remove
existing license information as this has to be done on a case by case
basis and the copyright holders might have to be consulted. This will
happen in a separate step.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne. See the previous patch in this series for the
methodology of how this patch was researched.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Greg Kroah-Hartman
commited |
e2be04c7f9 | |
This is a different approach from the first attempt in
Omar Sandoval
authored and
 Jens Axboe
commited |
89e4fdecb5 | |
There's some stuff still up in the air, let's not get stuck with a subpar ABI. I'll follow up with something better for 4.14. Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Omar Sandoval
authored and
Jens Axboe
commited |
1e6ec9ea89 | |
When generating bootable VM images certain systems (most notably s390x) require devices with 4k blocksize. This patch implements a new flag 'LO_FLAGS_BLOCKSIZE' which will set the physical blocksize to that of the underlying device, and allow to change the logical blocksize for up to the physical blocksize. Signed-off-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@fb.com> 
Hannes Reinecke
authored and
 Jens Axboe
commited |
f2c6df7dbf | |
If loop block is mounted via 'mount -o loop', it isn't easy to pass file descriptor opened as O_DIRECT, so this patch introduces a new command to support direct IO for this case. Cc: linux-api@vger.kernel.org Signed-off-by: Ming Lei <ming.lei@canonical.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com> 
Ming Lei
authored and
Jens Axboe
commited |
ab1cb278bc | |
This patches provides one interface for enabling direct IO from user space: - userspace(such as losetup) can pass 'file' which is opened/fcntl as O_DIRECT Also __loop_update_dio() is introduced to check if direct I/O can be used on current loop setting. The last big change is to introduce LO_FLAGS_DIRECT_IO flag for userspace to know if direct IO is used to access backing file. Cc: linux-api@vger.kernel.org Signed-off-by: Ming Lei <ming.lei@canonical.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
Ming Lei
authored and
Jens Axboe
commited |
2e5ab5f379 | |
Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Michael Kerrisk <mtk.manpages@gmail.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Dave Jones <davej@redhat.com> 
David Howells
commited |
607ca46e97 |