1 files changed, 104 insertions, 7 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index c77983ea86c..3d806820280 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -76,6 +76,8 @@
 #include <linux/splice.h>
 #include <linux/sysfs.h>
 #include <linux/miscdevice.h>
+#include <linux/falloc.h>
+
 #include <asm/uaccess.h>
 
 static DEFINE_IDR(loop_index_idr);
@@ -407,6 +409,29 @@ static int do_bio_filebacked(struct loop_device *lo, struct bio *bio)
                         }
                 }
 
+                /*
+                 * We use punch hole to reclaim the free space used by the
+                 * image a.k.a. discard. However we do support discard if
+                 * encryption is enabled, because it may give an attacker
+                 * useful information.
+                 */
+                if (bio->bi_rw & REQ_DISCARD) {
+                        struct file *file = lo->lo_backing_file;
+                        int mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE;
+
+                        if ((!file->f_op->fallocate) ||
+                            lo->lo_encrypt_key_size) {
+                                ret = -EOPNOTSUPP;
+                                goto out;
+                        }
+                        ret = file->f_op->fallocate(file, mode, pos,
+                                                    bio->bi_size);
+                        if (unlikely(ret && ret != -EINVAL &&
+                                     ret != -EOPNOTSUPP))
+                                ret = -EIO;
+                        goto out;
+                }
+
                 ret = lo_send(lo, bio, pos);
 
                 if ((bio->bi_rw & REQ_FUA) && !ret) {
@@ -622,7 +647,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
                 goto out_putf;
 
         fput(old_file);
-        if (max_part > 0)
+        if (lo->lo_flags & LO_FLAGS_PARTSCAN)
                 ioctl_by_bdev(bdev, BLKRRPART, 0);
         return 0;
 
@@ -699,16 +724,25 @@ static ssize_t loop_attr_autoclear_show(struct loop_device *lo, char *buf)
         return sprintf(buf, "%s\n", autoclear ? "1" : "0");
 }
 
+static ssize_t loop_attr_partscan_show(struct loop_device *lo, char *buf)
+{
+        int partscan = (lo->lo_flags & LO_FLAGS_PARTSCAN);
+
+        return sprintf(buf, "%s\n", partscan ? "1" : "0");
+}
+
 LOOP_ATTR_RO(backing_file);
 LOOP_ATTR_RO(offset);
 LOOP_ATTR_RO(sizelimit);
 LOOP_ATTR_RO(autoclear);
+LOOP_ATTR_RO(partscan);
 
 static struct attribute *loop_attrs[] = {
         &loop_attr_backing_file.attr,
         &loop_attr_offset.attr,
         &loop_attr_sizelimit.attr,
         &loop_attr_autoclear.attr,
+        &loop_attr_partscan.attr,
         NULL,
 };
 
@@ -729,6 +763,35 @@ static void loop_sysfs_exit(struct loop_device *lo)
                            &loop_attribute_group);
 }
 
+static void loop_config_discard(struct loop_device *lo)
+{
+        struct file *file = lo->lo_backing_file;
+        struct inode *inode = file->f_mapping->host;
+        struct request_queue *q = lo->lo_queue;
+
+        /*
+         * We use punch hole to reclaim the free space used by the
+         * image a.k.a. discard. However we do support discard if
+         * encryption is enabled, because it may give an attacker
+         * useful information.
+         */
+        if ((!file->f_op->fallocate) ||
+            lo->lo_encrypt_key_size) {
+                q->limits.discard_granularity = 0;
+                q->limits.discard_alignment = 0;
+                q->limits.max_discard_sectors = 0;
+                q->limits.discard_zeroes_data = 0;
+                queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
+                return;
+        }
+
+        q->limits.discard_granularity = inode->i_sb->s_blocksize;
+        q->limits.discard_alignment = inode->i_sb->s_blocksize;
+        q->limits.max_discard_sectors = UINT_MAX >> 9;
+        q->limits.discard_zeroes_data = 1;
+        queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
+}
+
 static int loop_set_fd(struct loop_device *lo, fmode_t mode,
                        struct block_device *bdev, unsigned int arg)
 {
@@ -829,7 +892,9 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
         }
         lo->lo_state = Lo_bound;
         wake_up_process(lo->lo_thread);
-        if (max_part > 0)
+        if (part_shift)
+                lo->lo_flags |= LO_FLAGS_PARTSCAN;
+        if (lo->lo_flags & LO_FLAGS_PARTSCAN)
                 ioctl_by_bdev(bdev, BLKRRPART, 0);
         return 0;
 
@@ -890,10 +955,11 @@ loop_init_xfer(struct loop_device *lo, struct loop_func_table *xfer,
         return err;
 }
 
-static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
+static int loop_clr_fd(struct loop_device *lo)
 {
         struct file *filp = lo->lo_backing_file;
         gfp_t gfp = lo->old_gfp_mask;
+        struct block_device *bdev = lo->lo_device;
 
         if (lo->lo_state != Lo_bound)
                 return -ENXIO;
@@ -922,7 +988,6 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
         lo->lo_offset = 0;
         lo->lo_sizelimit = 0;
         lo->lo_encrypt_key_size = 0;
-        lo->lo_flags = 0;
         lo->lo_thread = NULL;
         memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
         memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
@@ -940,8 +1005,11 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
         lo->lo_state = Lo_unbound;
         /* This is safe: open() is still holding a reference. */
         module_put(THIS_MODULE);
-        if (max_part > 0 && bdev)
+        if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev)
                 ioctl_by_bdev(bdev, BLKRRPART, 0);
+        lo->lo_flags = 0;
+        if (!part_shift)
+                lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
         mutex_unlock(&lo->lo_ctl_mutex);
         /*
          * Need not hold lo_ctl_mutex to fput backing file.
@@ -995,6 +1063,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
                 if (figure_loop_size(lo))
                         return -EFBIG;
         }
+        loop_config_discard(lo);
 
         memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
         memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE);
@@ -1010,6 +1079,13 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
              (info->lo_flags & LO_FLAGS_AUTOCLEAR))
                 lo->lo_flags ^= LO_FLAGS_AUTOCLEAR;
 
+        if ((info->lo_flags & LO_FLAGS_PARTSCAN) &&
+             !(lo->lo_flags & LO_FLAGS_PARTSCAN)) {
+                lo->lo_flags |= LO_FLAGS_PARTSCAN;
+                lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN;
+                ioctl_by_bdev(lo->lo_device, BLKRRPART, 0);
+        }
+
         lo->lo_encrypt_key_size = info->lo_encrypt_key_size;
         lo->lo_init[0] = info->lo_init[0];
         lo->lo_init[1] = info->lo_init[1];
@@ -1203,7 +1279,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
                 break;