forked from luck/tmp_suning_uos_patched
loop: Add LOOP_CONFIGURE ioctl
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>
This commit is contained in:
Martijn Coenen
Jens Axboe
parent
faf1d25440
commit
3448914e8c
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@ -228,6 +228,19 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
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blk_mq_unfreeze_queue(lo->lo_queue);
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}
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/**
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* loop_validate_block_size() - validates the passed in block size
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* @bsize: size to validate
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*/
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static int
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loop_validate_block_size(unsigned short bsize)
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{
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if (bsize < 512 || bsize > PAGE_SIZE || !is_power_of_2(bsize))
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return -EINVAL;
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return 0;
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}
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/**
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* loop_set_size() - sets device size and notifies userspace
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* @lo: struct loop_device to set the size for
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@ -1050,23 +1063,24 @@ loop_set_status_from_info(struct loop_device *lo,
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return 0;
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}
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static int loop_set_fd(struct loop_device *lo, fmode_t mode,
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struct block_device *bdev, unsigned int arg)
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static int loop_configure(struct loop_device *lo, fmode_t mode,
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struct block_device *bdev,
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const struct loop_config *config)
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{
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struct file *file;
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struct inode *inode;
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struct address_space *mapping;
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struct block_device *claimed_bdev = NULL;
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int lo_flags = 0;
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int error;
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loff_t size;
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bool partscan;
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unsigned short bsize;
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/* This is safe, since we have a reference from open(). */
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__module_get(THIS_MODULE);
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error = -EBADF;
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file = fget(arg);
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file = fget(config->fd);
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if (!file)
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goto out;
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@ -1075,7 +1089,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
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* here to avoid changing device under exclusive owner.
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*/
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if (!(mode & FMODE_EXCL)) {
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claimed_bdev = bd_start_claiming(bdev, loop_set_fd);
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claimed_bdev = bd_start_claiming(bdev, loop_configure);
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if (IS_ERR(claimed_bdev)) {
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error = PTR_ERR(claimed_bdev);
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goto out_putf;
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@ -1097,11 +1111,26 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
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mapping = file->f_mapping;
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inode = mapping->host;
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size = get_loop_size(lo, file);
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if ((config->info.lo_flags & ~LOOP_CONFIGURE_SETTABLE_FLAGS) != 0) {
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error = -EINVAL;
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goto out_unlock;
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}
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if (config->block_size) {
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error = loop_validate_block_size(config->block_size);
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if (error)
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goto out_unlock;
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}
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error = loop_set_status_from_info(lo, &config->info);
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if (error)
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goto out_unlock;
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if (!(file->f_mode & FMODE_WRITE) || !(mode & FMODE_WRITE) ||
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!file->f_op->write_iter)
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lo_flags |= LO_FLAGS_READ_ONLY;
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size = get_loop_size(lo, file);
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lo->lo_flags |= LO_FLAGS_READ_ONLY;
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error = loop_prepare_queue(lo);
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if (error)
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@ -1109,30 +1138,28 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
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error = 0;
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set_device_ro(bdev, (lo_flags & LO_FLAGS_READ_ONLY) != 0);
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set_device_ro(bdev, (lo->lo_flags & LO_FLAGS_READ_ONLY) != 0);
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lo->use_dio = false;
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lo->use_dio = lo->lo_flags & LO_FLAGS_DIRECT_IO;
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lo->lo_device = bdev;
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lo->lo_flags = lo_flags;
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lo->lo_backing_file = file;
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lo->transfer = NULL;
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lo->ioctl = NULL;
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lo->lo_sizelimit = 0;
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lo->old_gfp_mask = mapping_gfp_mask(mapping);
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mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
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if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
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if (!(lo->lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
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blk_queue_write_cache(lo->lo_queue, true, false);
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if (io_is_direct(lo->lo_backing_file) && inode->i_sb->s_bdev) {
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if (config->block_size)
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bsize = config->block_size;
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else if (io_is_direct(lo->lo_backing_file) && inode->i_sb->s_bdev)
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/* In case of direct I/O, match underlying block size */
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unsigned short bsize = bdev_logical_block_size(
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inode->i_sb->s_bdev);
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bsize = bdev_logical_block_size(inode->i_sb->s_bdev);
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else
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bsize = 512;
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blk_queue_logical_block_size(lo->lo_queue, bsize);
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blk_queue_physical_block_size(lo->lo_queue, bsize);
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blk_queue_io_min(lo->lo_queue, bsize);
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}
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blk_queue_logical_block_size(lo->lo_queue, bsize);
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blk_queue_physical_block_size(lo->lo_queue, bsize);
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blk_queue_io_min(lo->lo_queue, bsize);
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loop_update_rotational(lo);
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loop_update_dio(lo);
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@ -1155,14 +1182,14 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
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if (partscan)
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loop_reread_partitions(lo, bdev);
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if (claimed_bdev)
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bd_abort_claiming(bdev, claimed_bdev, loop_set_fd);
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bd_abort_claiming(bdev, claimed_bdev, loop_configure);
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return 0;
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out_unlock:
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mutex_unlock(&loop_ctl_mutex);
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out_bdev:
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if (claimed_bdev)
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bd_abort_claiming(bdev, claimed_bdev, loop_set_fd);
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bd_abort_claiming(bdev, claimed_bdev, loop_configure);
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out_putf:
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fput(file);
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out:
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@ -1582,8 +1609,9 @@ static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
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if (lo->lo_state != Lo_bound)
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return -ENXIO;
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if (arg < 512 || arg > PAGE_SIZE || !is_power_of_2(arg))
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return -EINVAL;
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err = loop_validate_block_size(arg);
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if (err)
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return err;
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if (lo->lo_queue->limits.logical_block_size == arg)
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return 0;
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@ -1645,8 +1673,27 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
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int err;
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switch (cmd) {
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case LOOP_SET_FD:
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return loop_set_fd(lo, mode, bdev, arg);
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case LOOP_SET_FD: {
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/*
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* Legacy case - pass in a zeroed out struct loop_config with
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* only the file descriptor set , which corresponds with the
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* default parameters we'd have used otherwise.
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*/
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struct loop_config config;
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memset(&config, 0, sizeof(config));
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config.fd = arg;
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return loop_configure(lo, mode, bdev, &config);
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}
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case LOOP_CONFIGURE: {
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struct loop_config config;
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if (copy_from_user(&config, argp, sizeof(config)))
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return -EFAULT;
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return loop_configure(lo, mode, bdev, &config);
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}
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case LOOP_CHANGE_FD:
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return loop_change_fd(lo, bdev, arg);
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case LOOP_CLR_FD:
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@ -1818,6 +1865,7 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
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case LOOP_CLR_FD:
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case LOOP_GET_STATUS64:
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case LOOP_SET_STATUS64:
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case LOOP_CONFIGURE:
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arg = (unsigned long) compat_ptr(arg);
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/* fall through */
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case LOOP_SET_FD:
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@ -31,6 +31,10 @@ enum {
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/* LO_FLAGS that can be cleared using LOOP_SET_STATUS(64) */
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#define LOOP_SET_STATUS_CLEARABLE_FLAGS (LO_FLAGS_AUTOCLEAR)
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/* LO_FLAGS that can be set using LOOP_CONFIGURE */
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#define LOOP_CONFIGURE_SETTABLE_FLAGS (LO_FLAGS_READ_ONLY | LO_FLAGS_AUTOCLEAR \
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| LO_FLAGS_PARTSCAN | LO_FLAGS_DIRECT_IO)
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#include <asm/posix_types.h> /* for __kernel_old_dev_t */
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#include <linux/types.h> /* for __u64 */
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@ -66,6 +70,22 @@ struct loop_info64 {
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__u64 lo_init[2];
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};
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/**
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* struct loop_config - Complete configuration for a loop device.
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* @fd: fd of the file to be used as a backing file for the loop device.
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* @block_size: block size to use; ignored if 0.
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* @info: struct loop_info64 to configure the loop device with.
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*
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* This structure is used with the LOOP_CONFIGURE ioctl, and can be used to
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* atomically setup and configure all loop device parameters at once.
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*/
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struct loop_config {
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__u32 fd;
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__u32 block_size;
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struct loop_info64 info;
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__u64 __reserved[8];
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};
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/*
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* Loop filter types
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*/
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@ -96,6 +116,7 @@ struct loop_info64 {
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#define LOOP_SET_CAPACITY 0x4C07
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#define LOOP_SET_DIRECT_IO 0x4C08
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#define LOOP_SET_BLOCK_SIZE 0x4C09
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#define LOOP_CONFIGURE 0x4C0A
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/* /dev/loop-control interface */
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#define LOOP_CTL_ADD 0x4C80
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