[PATCH v2 1/5] loop: Refactor size calculation
From: Martijn Coenen
Date: Wed Apr 22 2020 - 06:56:13 EST
figure_loop_size() calculates the loop size based on the passed in
parameters, but at the same time it updates the offset and sizelimit
parameters in the loop device configuration. That is a somewhat
unexpected side effect of a function with this name, and it is only only
needed by one of the two callers of this function - loop_set_status().
Move the lo_offset and lo_sizelimit assignment back into loop_set_status(),
and factor out a new function (loop_set_size()) to apply a newly
calculated size that has been validated to fit in sector_t, and notify
user-space.
loop_update_size() is now solely used by loop_set_capacity to compute an
updated size, and loop_set_status() uses a combination of functions to
validate the loop size, and only apply it later.
Signed-off-by: Martijn Coenen <maco@xxxxxxxxxxx>
---
drivers/block/loop.c | 88 ++++++++++++++++++++++++++++----------------
1 file changed, 56 insertions(+), 32 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index f1754262fc94..4f5c765c73d8 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -228,23 +228,42 @@ static void __loop_update_dio(struct loop_device *lo, bool dio)
blk_mq_unfreeze_queue(lo->lo_queue);
}
+/**
+ * loop_set_size - sets device size and notifies userspace
+ * @lo: struct loop_device to set the size for
+ * @size: new size of the loop device
+ *
+ * Callers must validate that the size passed into this function fits into
+ * a sector_t.
+ */
+static void loop_set_size(struct loop_device *lo, loff_t size)
+{
+ struct block_device *bdev = lo->lo_device;
+
+ set_capacity(lo->lo_disk, size);
+ bd_set_size(bdev, size << SECTOR_SHIFT);
+ /* let user-space know about the new size */
+ kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
+}
+
+/**
+ * loop_update_size - updates device size from the backing file
+ * @lo: struct loop_device to update the size for
+ *
+ * Recomputes the device size from the backing file, and updates the device
+ * with the new size.
+ */
static int
-figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
+loop_update_size(struct loop_device *lo)
{
- loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
+ loff_t size = get_loop_size(lo, lo->lo_backing_file);
sector_t x = (sector_t)size;
- struct block_device *bdev = lo->lo_device;
if (unlikely((loff_t)x != size))
return -EFBIG;
- if (lo->lo_offset != offset)
- lo->lo_offset = offset;
- if (lo->lo_sizelimit != sizelimit)
- lo->lo_sizelimit = sizelimit;
- set_capacity(lo->lo_disk, x);
- bd_set_size(bdev, (loff_t)get_capacity(bdev->bd_disk) << 9);
- /* let user-space know about the new size */
- kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
+
+ loop_set_size(lo, size);
+
return 0;
}
@@ -1040,11 +1059,8 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
loop_update_rotational(lo);
loop_update_dio(lo);
- set_capacity(lo->lo_disk, size);
- bd_set_size(bdev, size << 9);
loop_sysfs_init(lo);
- /* let user-space know about the new size */
- kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
+ loop_set_size(lo, size);
set_blocksize(bdev, S_ISBLK(inode->i_mode) ?
block_size(inode->i_bdev) : PAGE_SIZE);
@@ -1267,6 +1283,8 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
kuid_t uid = current_uid();
struct block_device *bdev;
bool partscan = false;
+ bool size_changed = false;
+ loff_t validated_size;
err = mutex_lock_killable(&loop_ctl_mutex);
if (err)
@@ -1288,6 +1306,14 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
if (lo->lo_offset != info->lo_offset ||
lo->lo_sizelimit != info->lo_sizelimit) {
+ size_t size = get_size(info->lo_offset, info->lo_sizelimit,
+ lo->lo_backing_file);
+ if ((loff_t)(sector_t)size != size) {
+ err = -EFBIG;
+ goto out_unlock;
+ }
+ size_changed = true;
+ validated_size = size;
sync_blockdev(lo->lo_device);
kill_bdev(lo->lo_device);
}
@@ -1295,6 +1321,15 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
/* I/O need to be drained during transfer transition */
blk_mq_freeze_queue(lo->lo_queue);
+ if (size_changed && lo->lo_device->bd_inode->i_mapping->nrpages) {
+ /* If any pages were dirtied after kill_bdev(), try again */
+ err = -EAGAIN;
+ pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
+ __func__, lo->lo_number, lo->lo_file_name,
+ lo->lo_device->bd_inode->i_mapping->nrpages);
+ goto out_unfreeze;
+ }
+
err = loop_release_xfer(lo);
if (err)
goto out_unfreeze;
@@ -1318,22 +1353,8 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
if (err)
goto out_unfreeze;
- if (lo->lo_offset != info->lo_offset ||
- lo->lo_sizelimit != info->lo_sizelimit) {
- /* kill_bdev should have truncated all the pages */
- if (lo->lo_device->bd_inode->i_mapping->nrpages) {
- err = -EAGAIN;
- pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
- __func__, lo->lo_number, lo->lo_file_name,
- lo->lo_device->bd_inode->i_mapping->nrpages);
- goto out_unfreeze;
- }
- if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit)) {
- err = -EFBIG;
- goto out_unfreeze;
- }
- }
-
+ lo->lo_offset = info->lo_offset;
+ lo->lo_sizelimit = info->lo_sizelimit;
memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE);
lo->lo_file_name[LO_NAME_SIZE-1] = 0;
@@ -1357,6 +1378,9 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
lo->lo_key_owner = uid;
}
+ if (size_changed)
+ loop_set_size(lo, validated_size);
+
loop_config_discard(lo);
/* update dio if lo_offset or transfer is changed */
@@ -1534,7 +1558,7 @@ static int loop_set_capacity(struct loop_device *lo)
if (unlikely(lo->lo_state != Lo_bound))
return -ENXIO;
- return figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit);
+ return loop_update_size(lo);
}
static int loop_set_dio(struct loop_device *lo, unsigned long arg)
--
2.26.2.303.gf8c07b1a785-goog