[PATCH v5 05/11] loop: Refactor loop_set_status() size calculation

Martijn Coenen
2020-05-13T13:39:03Z

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 use the newly factored out functions to validate and apply the newly
calculated size. This allows us to get rid of figure_loop_size() in a
follow-up commit.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martijn Coenen <maco@android.com>
---
drivers/block/loop.c | 37 +++++++++++++++++++------------------
1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index d9a756f8abd5..c134b3439483 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -250,11 +250,6 @@ figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
{
loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);

- if (lo->lo_offset != offset)
- lo->lo_offset = offset;
- if (lo->lo_sizelimit != sizelimit)
- lo->lo_sizelimit = sizelimit;
-
loop_set_size(lo, size);
}

@@ -1272,6 +1267,7 @@ 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;

err = mutex_lock_killable(&loop_ctl_mutex);
if (err)
@@ -1293,6 +1289,7 @@ 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_changed = true;
sync_blockdev(lo->lo_device);
kill_bdev(lo->lo_device);
}
@@ -1300,6 +1297,15 @@ 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;
@@ -1323,19 +1329,8 @@ 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;
- }
- figure_loop_size(lo, info->lo_offset, info->lo_sizelimit);
- }
-
+ 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;
@@ -1359,6 +1354,12 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
lo->lo_key_owner = uid;
}

+ if (size_changed) {
+ loff_t new_size = get_size(lo->lo_offset, lo->lo_sizelimit,
+ lo->lo_backing_file);
+ loop_set_size(lo, new_size);
+ }
+
loop_config_discard(lo);

/* update dio if lo_offset or transfer is changed */
--
2.26.2.645.ge9eca65c58-goog