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loop: block changing lo_offset/lo_sizelimit on mounted device #705

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loop: block changing lo_offset/lo_sizelimit on mounted device #705

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5 changes: 0 additions & 5 deletions block/bdev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -860,11 +860,6 @@ void blkdev_put_no_open(struct block_device *bdev)
put_device(&bdev->bd_device);
}

static bool bdev_writes_blocked(struct block_device *bdev)
{
return bdev->bd_writers < 0;
}

static void bdev_block_writes(struct block_device *bdev)
{
bdev->bd_writers--;
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16 changes: 16 additions & 0 deletions drivers/block/loop.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1239,6 +1239,22 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
goto out_unlock;
}

#ifndef CONFIG_BLK_DEV_WRITE_MOUNTED
/*
* Changing lo_offset or shrinking lo_sizelimit on a mounted
* device is equivalent to modifying the block device contents.
* Block this if writes to the device are blocked.
*/
if ((lo->lo_offset != info->lo_offset ||
(info->lo_sizelimit &&
(lo->lo_sizelimit == 0 ||
info->lo_sizelimit < lo->lo_sizelimit))) &&
bdev_writes_blocked(lo->lo_device)) {
err = -EBUSY;
goto out_unlock;
}
#endif

if (lo->lo_offset != info->lo_offset ||
lo->lo_sizelimit != info->lo_sizelimit) {
size_changed = true;
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5 changes: 5 additions & 0 deletions include/linux/blk_types.h
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Original file line number Diff line number Diff line change
Expand Up @@ -84,6 +84,11 @@ struct block_device {
#define bdev_whole(_bdev) \
((_bdev)->bd_disk->part0)

static inline bool bdev_writes_blocked(struct block_device *bdev)
{
return bdev->bd_writers < 0;
}

#define dev_to_bdev(device) \
container_of((device), struct block_device, bd_device)

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