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-rw-r--r--drivers/block/loop.c54
1 files changed, 54 insertions, 0 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 76c8da78212b..936cac3c3126 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -75,6 +75,7 @@
#include <linux/kthread.h>
#include <linux/splice.h>
#include <linux/sysfs.h>
+#include <linux/falloc.h>
#include <asm/uaccess.h>
@@ -484,6 +485,29 @@ 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) {
@@ -814,6 +838,35 @@ 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)
{
@@ -1090,6 +1143,7 @@ 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);
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