Commit 8e75fd89 authored by Nikolay Borisov's avatar Nikolay Borisov Committed by David Sterba
Browse files

btrfs: Stop using call_rcu for device freeing 



btrfs_device structs are freed from RCU context since device iteration
is protected by RCU. Currently this is achieved by using call_rcu since
no blocking functions are called within btrfs_free_device. Future
refactoring of pending/pinned chunks will require calling sleeping
functions.

This patch is in preparation for these changes by simply switching from
RCU callbacks to explicit calls of synchronize_rcu and calling
btrfs_free_device directly. This is functionally equivalent, making sure
that there are no readers at that time.

Signed-off-by: default avatarNikolay Borisov <nborisov@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 4ca73656

fs/btrfs/volumes.c

+8 −12
Original line number Diff line number Diff line
@@ -1231,14 +1231,6 @@ again: 
	mutex_unlock(&uuid_mutex);

}



static void free_device_rcu(struct rcu_head *head)

{

	struct btrfs_device *device;



	device = container_of(head, struct btrfs_device, rcu);

	btrfs_free_device(device);

}



static void btrfs_close_bdev(struct btrfs_device *device)

{

	if (!device->bdev)
@@ -1286,7 +1278,8 @@ static void btrfs_close_one_device(struct btrfs_device *device) 
	list_replace_rcu(&device->dev_list, &new_device->dev_list);

	new_device->fs_devices = device->fs_devices;



	call_rcu(&device->rcu, free_device_rcu);

	synchronize_rcu();

	btrfs_free_device(device);

}



static int close_fs_devices(struct btrfs_fs_devices *fs_devices)
@@ -2243,7 +2236,8 @@ int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path, 
		btrfs_scratch_superblocks(device->bdev, device->name->str);



	btrfs_close_bdev(device);

	call_rcu(&device->rcu, free_device_rcu);

	synchronize_rcu();

	btrfs_free_device(device);



	if (cur_devices->open_devices == 0) {

		while (fs_devices) {
@@ -2311,7 +2305,8 @@ void btrfs_rm_dev_replace_free_srcdev(struct btrfs_fs_info *fs_info, 
	}



	btrfs_close_bdev(srcdev);

	call_rcu(&srcdev->rcu, free_device_rcu);

	synchronize_rcu();

	btrfs_free_device(srcdev);



	/* if this is no devs we rather delete the fs_devices */

	if (!fs_devices->num_devices) {
@@ -2369,7 +2364,8 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev) 
	btrfs_scratch_superblocks(tgtdev->bdev, tgtdev->name->str);



	btrfs_close_bdev(tgtdev);

	call_rcu(&tgtdev->rcu, free_device_rcu);

	synchronize_rcu();

	btrfs_free_device(tgtdev);

}



static struct btrfs_device *btrfs_find_device_by_path(

fs/btrfs/volumes.h

+0 −1
Original line number Diff line number Diff line
@@ -118,7 +118,6 @@ struct btrfs_device { 
	struct scrub_ctx *scrub_ctx;



	struct btrfs_work work;

	struct rcu_head rcu;



	/* readahead state */

	atomic_t reada_in_flight;

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