On Tue, 8 Jul 2014 12:08:19 +0800, Liu Bo wrote:
> On Tue, Jul 08, 2014 at 02:38:37AM +0800, Anand Jain wrote:
>> (for review comments pls).
>>
>> btrfs_scan_one_device() needs SB, instead of doing it from scratch could
>> use btrfs_get_bdev_and_sb()
>>
>> Signed-off-by: Anand Jain <Anand.Jain@xxxxxxxxxx>
>> ---
>> fs/btrfs/volumes.c | 51 ++++++---------------------------------------------
>> 1 file changed, 6 insertions(+), 45 deletions(-)
>>
>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>> index c166355..94e6131 100644
>> --- a/fs/btrfs/volumes.c
>> +++ b/fs/btrfs/volumes.c
>> @@ -1053,14 +1053,11 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
>> {
>> struct btrfs_super_block *disk_super;
>> struct block_device *bdev;
>> - struct page *page;
>> - void *p;
>> int ret = -EINVAL;
>> u64 devid;
>> u64 transid;
>> u64 total_devices;
>> - u64 bytenr;
>> - pgoff_t index;
>> + struct buffer_head *bh;
>>
>> /*
>> * we would like to check all the supers, but that would make
>> @@ -1068,44 +1065,12 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
>> * So, we need to add a special mount option to scan for
>> * later supers, using BTRFS_SUPER_MIRROR_MAX instead
>> */
>> - bytenr = btrfs_sb_offset(0);
>> mutex_lock(&uuid_mutex);
>>
>> - bdev = blkdev_get_by_path(path, flags, holder);
>> -
>> - if (IS_ERR(bdev)) {
>> - ret = PTR_ERR(bdev);
>> + ret = btrfs_get_bdev_and_sb(path, flags, holder, 0, &bdev, &bh);
>> + if (ret)
>> goto error;
>> - }
>> -
>> - /* make sure our super fits in the device */
>> - if (bytenr + PAGE_CACHE_SIZE >= i_size_read(bdev->bd_inode))
>> - goto error_bdev_put;
>> -
>> - /* make sure our super fits in the page */
>> - if (sizeof(*disk_super) > PAGE_CACHE_SIZE)
>> - goto error_bdev_put;
>> -
>> - /* make sure our super doesn't straddle pages on disk */
>> - index = bytenr >> PAGE_CACHE_SHIFT;
>> - if ((bytenr + sizeof(*disk_super) - 1) >> PAGE_CACHE_SHIFT != index)
>> - goto error_bdev_put;
>
> Apparently btrfs_get_bdev_and_sb() lacks the above two checks, otherwise looks good.
In fact, our disk_super size is constant and <= min page size (4K), and we are sure that
it is impossible that the super block is cross the block, so the above two checks are unnecessary.
Thanks
Miao
>
> thanks,
> -liubo
>
>> -
>> - /* pull in the page with our super */
>> - page = read_cache_page_gfp(bdev->bd_inode->i_mapping,
>> - index, GFP_NOFS);
>> -
>> - if (IS_ERR_OR_NULL(page))
>> - goto error_bdev_put;
>> -
>> - p = kmap(page);
>> -
>> - /* align our pointer to the offset of the super block */
>> - disk_super = p + (bytenr & ~PAGE_CACHE_MASK);
>> -
>> - if (btrfs_super_bytenr(disk_super) != bytenr ||
>> - btrfs_super_magic(disk_super) != BTRFS_MAGIC)
>> - goto error_unmap;
>> + disk_super = (struct btrfs_super_block *) bh->b_data;
>>
>> devid = btrfs_stack_device_id(&disk_super->dev_item);
>> transid = btrfs_super_generation(disk_super);
>> @@ -1125,13 +1090,9 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
>> printk(KERN_CONT "devid %llu transid %llu %s\n", devid, transid, path);
>> }
>>
>> -
>> -error_unmap:
>> - kunmap(page);
>> - page_cache_release(page);
>> -
>> -error_bdev_put:
>> + brelse(bh);
>> blkdev_put(bdev, flags);
>> +
>> error:
>> mutex_unlock(&uuid_mutex);
>> return ret;
>> --
>> 2.0.0.257.g75cc6c6
>>
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