Re: [PATCH 07/26] Btrfs: add two more find_device() methods
On Thu, 8 Nov 2012 22:24:51 +0800, Liu Bo wrote:
> On Tue, Nov 06, 2012 at 05:38:25PM +0100, Stefan Behrens wrote:
>> The new function btrfs_find_device_missing_or_by_path() will be
>> used for the device replace procedure. This function itself calls
>> the second new function btrfs_find_device_by_path().
>> Unfortunately, it is not possible to currently make the rest of the
>> code use these functions as well, since all functions that look
>> similar at first view are all a little bit different in what they
>> are doing. But in the future, new code could benefit from these
>> two new functions, and currently, device replace uses them.
>>
>> Signed-off-by: Stefan Behrens
>> ---
>> fs/btrfs/volumes.c | 74
>> ++
>> fs/btrfs/volumes.h | 5
>> 2 files changed, 79 insertions(+)
>>
>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>> index eeed97d..bcd3097 100644
>> --- a/fs/btrfs/volumes.c
>> +++ b/fs/btrfs/volumes.c
>> @@ -1512,6 +1512,80 @@ error_undo:
>> goto error_brelse;
>> }
>>
>> +int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,
>> + struct btrfs_device **device)
>> +{
>> +int ret = 0;
>> +struct btrfs_super_block *disk_super;
>> +u64 devid;
>> +u8 *dev_uuid;
>> +struct block_device *bdev;
>> +struct buffer_head *bh = NULL;
>> +
>> +*device = NULL;
>> +mutex_lock(&uuid_mutex);
>
> Since the caller have held volume_mutex, we can get rid of the
> mutex_lock here, can't we?
>
Yes, you are right.
>> +bdev = blkdev_get_by_path(device_path, FMODE_READ,
>> + root->fs_info->bdev_holder);
>> +if (IS_ERR(bdev)) {
>> +ret = PTR_ERR(bdev);
>> +bdev = NULL;
>> +goto out;
>> +}
>> +
>> +set_blocksize(bdev, 4096);
>> +invalidate_bdev(bdev);
>> +bh = btrfs_read_dev_super(bdev);
>> +if (!bh) {
>> +ret = -EINVAL;
>> +goto out;
>> +}
>
> I made a scan for this 'get bdev & bh' in the code, I think
> maybe we can make a function,
> func_get(device_path, flags, mode, &bdev, &bh, flush)
>
> where we need to take care of setting bdev = NULL, bh = NULL, and
> 'flush' is for filemap_bdev(). Besides, we also need to make
> some proper error handling.
Good idea for a cleanup! I have now added such a function. It improves
the readability. And it is only one place to make changes in the future
(e.g. when it is time to replace the "short term measure" commit
3c4bb26b213 which added the flushing code as a temporary workaround).
Thanks for your comments!
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Re: [PATCH 07/26] Btrfs: add two more find_device() methods
On Tue, Nov 06, 2012 at 05:38:25PM +0100, Stefan Behrens wrote:
> The new function btrfs_find_device_missing_or_by_path() will be
> used for the device replace procedure. This function itself calls
> the second new function btrfs_find_device_by_path().
> Unfortunately, it is not possible to currently make the rest of the
> code use these functions as well, since all functions that look
> similar at first view are all a little bit different in what they
> are doing. But in the future, new code could benefit from these
> two new functions, and currently, device replace uses them.
>
> Signed-off-by: Stefan Behrens
> ---
> fs/btrfs/volumes.c | 74
> ++
> fs/btrfs/volumes.h | 5
> 2 files changed, 79 insertions(+)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index eeed97d..bcd3097 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1512,6 +1512,80 @@ error_undo:
> goto error_brelse;
> }
>
> +int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,
> + struct btrfs_device **device)
> +{
> + int ret = 0;
> + struct btrfs_super_block *disk_super;
> + u64 devid;
> + u8 *dev_uuid;
> + struct block_device *bdev;
> + struct buffer_head *bh = NULL;
> +
> + *device = NULL;
> + mutex_lock(&uuid_mutex);
Since the caller have held volume_mutex, we can get rid of the
mutex_lock here, can't we?
> + bdev = blkdev_get_by_path(device_path, FMODE_READ,
> + root->fs_info->bdev_holder);
> + if (IS_ERR(bdev)) {
> + ret = PTR_ERR(bdev);
> + bdev = NULL;
> + goto out;
> + }
> +
> + set_blocksize(bdev, 4096);
> + invalidate_bdev(bdev);
> + bh = btrfs_read_dev_super(bdev);
> + if (!bh) {
> + ret = -EINVAL;
> + goto out;
> + }
I made a scan for this 'get bdev & bh' in the code, I think
maybe we can make a function,
func_get(device_path, flags, mode, &bdev, &bh, flush)
where we need to take care of setting bdev = NULL, bh = NULL, and
'flush' is for filemap_bdev(). Besides, we also need to make
some proper error handling.
thanks,
liubo
> + disk_super = (struct btrfs_super_block *)bh->b_data;
> + devid = btrfs_stack_device_id(&disk_super->dev_item);
> + dev_uuid = disk_super->dev_item.uuid;
> + *device = btrfs_find_device(root, devid, dev_uuid,
> + disk_super->fsid);
> + brelse(bh);
> + if (!*device)
> + ret = -ENOENT;
> +out:
> + mutex_unlock(&uuid_mutex);
> + if (bdev)
> + blkdev_put(bdev, FMODE_READ);
> + return ret;
> +}
> +
> +int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
> + char *device_path,
> + struct btrfs_device **device)
> +{
> + *device = NULL;
> + if (strcmp(device_path, "missing") == 0) {
> + struct list_head *devices;
> + struct btrfs_device *tmp;
> +
> + devices = &root->fs_info->fs_devices->devices;
> + /*
> + * It is safe to read the devices since the volume_mutex
> + * is held by the caller.
> + */
> + list_for_each_entry(tmp, devices, dev_list) {
> + if (tmp->in_fs_metadata && !tmp->bdev) {
> + *device = tmp;
> + break;
> + }
> + }
> +
> + if (!*device) {
> + pr_err("btrfs: no missing device found\n");
> + return -ENOENT;
> + }
> +
> + return 0;
> + } else {
> + return btrfs_find_device_by_path(root, device_path, device);
> + }
> +}
> +
> /*
> * does all the dirty work required for changing file system's UUID.
> */
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 1789cda..657bb12 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -268,6 +268,11 @@ int btrfs_scan_one_device(const char *path, fmode_t
> flags, void *holder,
> struct btrfs_fs_devices **fs_devices_ret);
> int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
> void btrfs_close_extra_devices(struct btrfs_fs_devices *fs_devices);
> +int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
> + char *device_path,
> + struct btrfs_device **device);
> +int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,
> + struct btrfs_device **device);
> int btrfs_add_device(struct btrfs_trans_handle *trans,
>struct btrfs_root *root,
>struct btrfs_device *device);
> --
> 1.8.0
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btr
[PATCH 07/26] Btrfs: add two more find_device() methods
The new function btrfs_find_device_missing_or_by_path() will be
used for the device replace procedure. This function itself calls
the second new function btrfs_find_device_by_path().
Unfortunately, it is not possible to currently make the rest of the
code use these functions as well, since all functions that look
similar at first view are all a little bit different in what they
are doing. But in the future, new code could benefit from these
two new functions, and currently, device replace uses them.
Signed-off-by: Stefan Behrens
---
fs/btrfs/volumes.c | 74 ++
fs/btrfs/volumes.h | 5
2 files changed, 79 insertions(+)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index eeed97d..bcd3097 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1512,6 +1512,80 @@ error_undo:
goto error_brelse;
}
+int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,
+ struct btrfs_device **device)
+{
+ int ret = 0;
+ struct btrfs_super_block *disk_super;
+ u64 devid;
+ u8 *dev_uuid;
+ struct block_device *bdev;
+ struct buffer_head *bh = NULL;
+
+ *device = NULL;
+ mutex_lock(&uuid_mutex);
+ bdev = blkdev_get_by_path(device_path, FMODE_READ,
+ root->fs_info->bdev_holder);
+ if (IS_ERR(bdev)) {
+ ret = PTR_ERR(bdev);
+ bdev = NULL;
+ goto out;
+ }
+
+ set_blocksize(bdev, 4096);
+ invalidate_bdev(bdev);
+ bh = btrfs_read_dev_super(bdev);
+ if (!bh) {
+ ret = -EINVAL;
+ goto out;
+ }
+ disk_super = (struct btrfs_super_block *)bh->b_data;
+ devid = btrfs_stack_device_id(&disk_super->dev_item);
+ dev_uuid = disk_super->dev_item.uuid;
+ *device = btrfs_find_device(root, devid, dev_uuid,
+ disk_super->fsid);
+ brelse(bh);
+ if (!*device)
+ ret = -ENOENT;
+out:
+ mutex_unlock(&uuid_mutex);
+ if (bdev)
+ blkdev_put(bdev, FMODE_READ);
+ return ret;
+}
+
+int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
+char *device_path,
+struct btrfs_device **device)
+{
+ *device = NULL;
+ if (strcmp(device_path, "missing") == 0) {
+ struct list_head *devices;
+ struct btrfs_device *tmp;
+
+ devices = &root->fs_info->fs_devices->devices;
+ /*
+* It is safe to read the devices since the volume_mutex
+* is held by the caller.
+*/
+ list_for_each_entry(tmp, devices, dev_list) {
+ if (tmp->in_fs_metadata && !tmp->bdev) {
+ *device = tmp;
+ break;
+ }
+ }
+
+ if (!*device) {
+ pr_err("btrfs: no missing device found\n");
+ return -ENOENT;
+ }
+
+ return 0;
+ } else {
+ return btrfs_find_device_by_path(root, device_path, device);
+ }
+}
+
/*
* does all the dirty work required for changing file system's UUID.
*/
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 1789cda..657bb12 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -268,6 +268,11 @@ int btrfs_scan_one_device(const char *path, fmode_t flags,
void *holder,
struct btrfs_fs_devices **fs_devices_ret);
int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
void btrfs_close_extra_devices(struct btrfs_fs_devices *fs_devices);
+int btrfs_find_device_missing_or_by_path(struct btrfs_root *root,
+char *device_path,
+struct btrfs_device **device);
+int btrfs_find_device_by_path(struct btrfs_root *root, char *device_path,
+ struct btrfs_device **device);
int btrfs_add_device(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct btrfs_device *device);
--
1.8.0
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