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SubjectRe: [PATCH -V7 6/9] ext4: Add get_fsid callback


On 05/12/2010 11:50 PM, Aneesh Kumar K.V Wrote:
> Acked-by: Serge Hallyn <serue@us.ibm.com>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
> fs/ext4/super.c | 15 +++++++++++++++
> 1 files changed, 15 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index e14d22c..fc7d464 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1049,6 +1049,19 @@ static int bdev_try_to_free_page(struct super_block *sb, struct page *page,
> return try_to_free_buffers(page);
> }
>
> +static int ext4_get_fsid(struct super_block *sb, struct uuid *fsid)
> +{
> + struct ext4_sb_info *sbi = EXT4_SB(sb);
> + struct ext4_super_block *es = sbi->s_es;
> +
> + memcpy(fsid->uuid, es->s_uuid, sizeof(fsid->uuid));
> + /*
> + * We may want to make sure we return error if the s_uuid is not
> + * exactly unique
> + */
> + return 0;
> +}
> +
> #ifdef CONFIG_QUOTA
> #define QTYPE2NAME(t) ((t) == USRQUOTA ? "user" : "group")
> #define QTYPE2MOPT(on, t) ((t) == USRQUOTA?((on)##USRJQUOTA):((on)##GRPJQUOTA))
> @@ -1109,6 +1122,7 @@ static const struct super_operations ext4_sops = {
> .quota_write = ext4_quota_write,
> #endif
> .bdev_try_to_free_page = bdev_try_to_free_page,
> + .get_fsid = ext4_get_fsid,
> };
>
> static const struct super_operations ext4_nojournal_sops = {
> @@ -1128,6 +1142,7 @@ static const struct super_operations ext4_nojournal_sops = {
> .quota_write = ext4_quota_write,
> #endif
> .bdev_try_to_free_page = bdev_try_to_free_page,
> + .get_fsid = ext4_get_fsid,
> };
>

Hi Aneesh,

Just wondering why not call sb->s_op->statfs() to get the fsid in do_sys_name_to_handle() ?
The overhead is a little bit more code to get fsid from struct kstatfs, but we can gain,
1) avoid to have one more callback in struct super_operations.
2) more file system can be supported (since most of file systems have statfs() call back)

Thanks.
--
Coly Li
SuSE Labs


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