loop: factor out a loop_assign_backing_file helper

Split the code for setting up a backing file into a helper in preparation
of adding more code to this path.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20250131120120.1315125-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index c05fe27a96b64f1f1ea3868510fdd0c7f4937f55..bc839d6e73b7ffe09d1126ab09543088833ed68a 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -573,6 +573,14 @@ static int loop_validate_file(struct file *file, struct block_device *bdev)
        return 0;
 }
 
+static void loop_assign_backing_file(struct loop_device *lo, struct file *file)
+{
+       lo->lo_backing_file = file;
+       lo->old_gfp_mask = mapping_gfp_mask(file->f_mapping);
+       mapping_set_gfp_mask(file->f_mapping,
+                       lo->old_gfp_mask & ~(__GFP_IO | __GFP_FS));
+}
+
 /*
  * loop_change_fd switched the backing store of a loopback device to
  * a new file. This is useful for operating system installers to free up
@@ -626,10 +634,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
        disk_force_media_change(lo->lo_disk);
        memflags = blk_mq_freeze_queue(lo->lo_queue);
        mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
-       lo->lo_backing_file = file;
-       lo->old_gfp_mask = mapping_gfp_mask(file->f_mapping);
-       mapping_set_gfp_mask(file->f_mapping,
-                            lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
+       loop_assign_backing_file(lo, file);
        loop_update_dio(lo);
        blk_mq_unfreeze_queue(lo->lo_queue, memflags);
        partscan = lo->lo_flags & LO_FLAGS_PARTSCAN;
@@ -1019,7 +1024,6 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
                          const struct loop_config *config)
 {
        struct file *file = fget(config->fd);
-       struct address_space *mapping;
        struct queue_limits lim;
        int error;
        loff_t size;
@@ -1055,8 +1059,6 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
        if (error)
                goto out_unlock;
 
-       mapping = file->f_mapping;
-
        if ((config->info.lo_flags & ~LOOP_CONFIGURE_SETTABLE_FLAGS) != 0) {
                error = -EINVAL;
                goto out_unlock;
@@ -1088,9 +1090,7 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
        set_disk_ro(lo->lo_disk, (lo->lo_flags & LO_FLAGS_READ_ONLY) != 0);
 
        lo->lo_device = bdev;
-       lo->lo_backing_file = file;
-       lo->old_gfp_mask = mapping_gfp_mask(mapping);
-       mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
+       loop_assign_backing_file(lo, file);
 
        lim = queue_limits_start_update(lo->lo_queue);
        loop_update_limits(lo, &lim, config->block_size);