Re: Re: [PATCH] erofs: support for mounting a single block device with multiple devices

[Jia Zhu]

在 2023/3/1 15:08, Gao Xiang 写道:
> Hi Jia,
>
> On 2023/3/1 15:04, Jia Zhu wrote:
> > In order to support mounting multi-layer container image as a block
> > device, add single block device with multiple devices feature for EROFS.
>
> In order to support mounting multi-blob container image as a single
> flattened block device, add flattened block device feature for EROFS.
Thanks, I would revise it.
> > In this mode, all meta/data contents will be mapped into one block 
> > address.
> > User could directly mount the block device by EROFS.
> >
> > Signed-off-by: Jia Zhu <zhujia.zj@xxxxxxxxxxxxx>
> > Reviewed-by: Xin Yin <yinxin.x@xxxxxxxxxxxxx>
> > ---
> >   fs/erofs/data.c  | 8 ++++++--
> >   fs/erofs/super.c | 5 +++++
> >   2 files changed, 11 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> > index e16545849ea7..870b1f7fe1d4 100644
> > --- a/fs/erofs/data.c
> > +++ b/fs/erofs/data.c
> > @@ -195,9 +195,9 @@ int erofs_map_dev(struct super_block *sb, struct 
> > erofs_map_dev *map)
> >   {
> >       struct erofs_dev_context *devs = EROFS_SB(sb)->devs;
> >       struct erofs_device_info *dif;
> > +    bool flatdev = !!sb->s_bdev;
>
> I'd like to land it in sbi and set it in advance?
I'll revise that in next version.
> Also, did you test this patch?

I've tested the patch using the following steps mentioned by
https://github.com/dragonflyoss/image-service/pull/1111

1. Compose a (nbd)block device from an EROFS image.
2. mount -t erofs /dev/nbdx /mnt/
3. compare the md5sum between source dir and /mnt dir.

> Thanks,
> Gao Xiang
>
>
> >       int id;
> > -    /* primary device by default */
> >       map->m_bdev = sb->s_bdev;
> >       map->m_daxdev = EROFS_SB(sb)->dax_dev;
> >       map->m_dax_part_off = EROFS_SB(sb)->dax_part_off;
> > @@ -210,12 +210,16 @@ int erofs_map_dev(struct super_block *sb, struct 
> > erofs_map_dev *map)
> >               up_read(&devs->rwsem);
> >               return -ENODEV;
> >           }
> > +        if (flatdev) {
> > +            map->m_pa += blknr_to_addr(dif->mapped_blkaddr);
> > +            map->m_deviceid = 0;
> > +        }
> >           map->m_bdev = dif->bdev;
> >           map->m_daxdev = dif->dax_dev;
> >           map->m_dax_part_off = dif->dax_part_off;
> >           map->m_fscache = dif->fscache;
> >           up_read(&devs->rwsem);
> > -    } else if (devs->extra_devices) {
> > +    } else if (devs->extra_devices && !flatdev) {
> >           down_read(&devs->rwsem);
> >           idr_for_each_entry(&devs->tree, dif, id) {
> >               erofs_off_t startoff, length;
> > diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> > index 19b1ae79cec4..4f9725b0950c 100644
> > --- a/fs/erofs/super.c
> > +++ b/fs/erofs/super.c
> > @@ -226,6 +226,7 @@ static int erofs_init_device(struct erofs_buf 
> > *buf, struct super_block *sb,
> >       struct erofs_fscache *fscache;
> >       struct erofs_deviceslot *dis;
> >       struct block_device *bdev;
> > +    bool flatdev = !!sb->s_bdev;
> >       void *ptr;
> >       ptr = erofs_read_metabuf(buf, sb, erofs_blknr(*pos), EROFS_KMAP);
> > @@ -248,6 +249,10 @@ static int erofs_init_device(struct erofs_buf 
> > *buf, struct super_block *sb,
> >           if (IS_ERR(fscache))
> >               return PTR_ERR(fscache);
> >           dif->fscache = fscache;
> > +    } else if (flatdev) {
> > +        dif->bdev = sb->s_bdev;
> > +        dif->dax_dev = EROFS_SB(sb)->dax_dev;
> > +        dif->dax_part_off = sbi->dax_part_off;
> >       } else {
> >           bdev = blkdev_get_by_path(dif->path, FMODE_READ | FMODE_EXCL,
> >                         sb->s_type);