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Subject[PATCH 5.15 086/230] btrfs: add a btrfs_get_dev_args_from_path helper
Date
From: Josef Bacik <josef@toxicpanda.com>

[ Upstream commit faa775c41d655a4786e9d53cb075a77bb5a75f66 ]

We are going to want to populate our device lookup args outside of any
locks and then do the actual device lookup later, so add a helper to do
this work and make btrfs_find_device_by_devspec() use this helper for
now.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/volumes.c | 96 ++++++++++++++++++++++++++++++----------------
fs/btrfs/volumes.h | 4 ++
2 files changed, 68 insertions(+), 32 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 53417a1c5402..8d09e6d442b2 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2361,45 +2361,81 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev)
btrfs_free_device(tgtdev);
}

-static struct btrfs_device *btrfs_find_device_by_path(
- struct btrfs_fs_info *fs_info, const char *device_path)
+/**
+ * Populate args from device at path
+ *
+ * @fs_info: the filesystem
+ * @args: the args to populate
+ * @path: the path to the device
+ *
+ * This will read the super block of the device at @path and populate @args with
+ * the devid, fsid, and uuid. This is meant to be used for ioctls that need to
+ * lookup a device to operate on, but need to do it before we take any locks.
+ * This properly handles the special case of "missing" that a user may pass in,
+ * and does some basic sanity checks. The caller must make sure that @path is
+ * properly NUL terminated before calling in, and must call
+ * btrfs_put_dev_args_from_path() in order to free up the temporary fsid and
+ * uuid buffers.
+ *
+ * Return: 0 for success, -errno for failure
+ */
+int btrfs_get_dev_args_from_path(struct btrfs_fs_info *fs_info,
+ struct btrfs_dev_lookup_args *args,
+ const char *path)
{
- BTRFS_DEV_LOOKUP_ARGS(args);
- int ret = 0;
struct btrfs_super_block *disk_super;
struct block_device *bdev;
- struct btrfs_device *device;
+ int ret;

- ret = btrfs_get_bdev_and_sb(device_path, FMODE_READ,
- fs_info->bdev_holder, 0, &bdev, &disk_super);
- if (ret)
- return ERR_PTR(ret);
+ if (!path || !path[0])
+ return -EINVAL;
+ if (!strcmp(path, "missing")) {
+ args->missing = true;
+ return 0;
+ }
+
+ args->uuid = kzalloc(BTRFS_UUID_SIZE, GFP_KERNEL);
+ args->fsid = kzalloc(BTRFS_FSID_SIZE, GFP_KERNEL);
+ if (!args->uuid || !args->fsid) {
+ btrfs_put_dev_args_from_path(args);
+ return -ENOMEM;
+ }

- args.devid = btrfs_stack_device_id(&disk_super->dev_item);
- args.uuid = disk_super->dev_item.uuid;
+ ret = btrfs_get_bdev_and_sb(path, FMODE_READ, fs_info->bdev_holder, 0,
+ &bdev, &disk_super);
+ if (ret)
+ return ret;
+ args->devid = btrfs_stack_device_id(&disk_super->dev_item);
+ memcpy(args->uuid, disk_super->dev_item.uuid, BTRFS_UUID_SIZE);
if (btrfs_fs_incompat(fs_info, METADATA_UUID))
- args.fsid = disk_super->metadata_uuid;
+ memcpy(args->fsid, disk_super->metadata_uuid, BTRFS_FSID_SIZE);
else
- args.fsid = disk_super->fsid;
-
- device = btrfs_find_device(fs_info->fs_devices, &args);
-
+ memcpy(args->fsid, disk_super->fsid, BTRFS_FSID_SIZE);
btrfs_release_disk_super(disk_super);
- if (!device)
- device = ERR_PTR(-ENOENT);
blkdev_put(bdev, FMODE_READ);
- return device;
+ return 0;
}

/*
- * Lookup a device given by device id, or the path if the id is 0.
+ * Only use this jointly with btrfs_get_dev_args_from_path() because we will
+ * allocate our ->uuid and ->fsid pointers, everybody else uses local variables
+ * that don't need to be freed.
*/
+void btrfs_put_dev_args_from_path(struct btrfs_dev_lookup_args *args)
+{
+ kfree(args->uuid);
+ kfree(args->fsid);
+ args->uuid = NULL;
+ args->fsid = NULL;
+}
+
struct btrfs_device *btrfs_find_device_by_devspec(
struct btrfs_fs_info *fs_info, u64 devid,
const char *device_path)
{
BTRFS_DEV_LOOKUP_ARGS(args);
struct btrfs_device *device;
+ int ret;

if (devid) {
args.devid = devid;
@@ -2409,18 +2445,14 @@ struct btrfs_device *btrfs_find_device_by_devspec(
return device;
}

- if (!device_path || !device_path[0])
- return ERR_PTR(-EINVAL);
-
- if (strcmp(device_path, "missing") == 0) {
- args.missing = true;
- device = btrfs_find_device(fs_info->fs_devices, &args);
- if (!device)
- return ERR_PTR(-ENOENT);
- return device;
- }
-
- return btrfs_find_device_by_path(fs_info, device_path);
+ ret = btrfs_get_dev_args_from_path(fs_info, &args, device_path);
+ if (ret)
+ return ERR_PTR(ret);
+ device = btrfs_find_device(fs_info->fs_devices, &args);
+ btrfs_put_dev_args_from_path(&args);
+ if (!device)
+ return ERR_PTR(-ENOENT);
+ return device;
}

/*
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index f3b1380f45ad..d1df03f77e29 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -487,9 +487,13 @@ void btrfs_assign_next_active_device(struct btrfs_device *device,
struct btrfs_device *btrfs_find_device_by_devspec(struct btrfs_fs_info *fs_info,
u64 devid,
const char *devpath);
+int btrfs_get_dev_args_from_path(struct btrfs_fs_info *fs_info,
+ struct btrfs_dev_lookup_args *args,
+ const char *path);
struct btrfs_device *btrfs_alloc_device(struct btrfs_fs_info *fs_info,
const u64 *devid,
const u8 *uuid);
+void btrfs_put_dev_args_from_path(struct btrfs_dev_lookup_args *args);
void btrfs_free_device(struct btrfs_device *device);
int btrfs_rm_device(struct btrfs_fs_info *fs_info,
const char *device_path, u64 devid,
--
2.35.1


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