loop: Refactor loop_set_status() size calculation

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.

Signed-off-by: Martijn Coenen <maco@android.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index d9a756f..c134b34 100644 (file)
--- 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 */