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 <[email protected]> >> --- >> 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 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >> the body of a message to [email protected] >> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
