Hi Hongbo,
I think the subject can be updated as:
`erofs-utils: fix file handle encoding for 64-bit NIDs`
On Tue, Apr 29, 2025 at 01:11:39AM +0000, Hongbo Li wrote:
> In erofs, the inode number has the location information of
> files. The default encode_fh uses the ino32, this will lack
> of some information when the file is too big. So we need
> the internal helpers to encode filehandle.
>
> Since i_generation in EROFS is not used, here we only encode
> the nid into file handle when it is exported. So it is easy
> to parse the dentry from file handle.
If `FILEID_INO64_GEN_PARENT` is used, I don't think
the generation number should be emitted, as documented as:
`
/*
* 64 bit inode number, 32 bit generation number.
*/
FILEID_INO64_GEN = 0x81,
/*
* 64 bit inode number, 32 bit generation number,
* 64 bit parent inode number, 32 bit parent generation.
*/
FILEID_INO64_GEN_PARENT = 0x82,
`
Even the generation number is 0 but we might use
i_generation for some remote update use cases
in the future.
>
> It is easy to reproduce test:
> 1. prepare an erofs image with nid bigger than UINT_MAX
> 2. mount -t erofs foo.img /mnt/erofs
> 3. set exportfs with configuration: /mnt/erofs *(rw,sync,
> no_root_squash)
> 4. mount -t nfs $IP:/mnt/erofs /mnt/nfs
> 5. md5sum /mnt/nfs/foo # foo is the file which nid bigger
> than UINT_MAX.
> For overlayfs case, the under filesystem's file handle is
> encoded in ovl_fb.fid, it is same as NFS's case.
Can we have a way to add a testcase for the overlayfs case:
since it's somewhat complex to write a testcase with nfs
above.
>
> Fixes: 3e917cc305c6 ("erofs: make filesystem exportable")
> Signed-off-by: Hongbo Li <lihongb...@huawei.com>
> ---
> fs/erofs/super.c | 51 ++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 43 insertions(+), 8 deletions(-)
>
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index cadec6b1b554..8f787c47e04d 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -511,24 +511,59 @@ static int erofs_fc_parse_param(struct fs_context *fc,
> return 0;
> }
>
> -static struct inode *erofs_nfs_get_inode(struct super_block *sb,
> - u64 ino, u32 generation)
> +static int erofs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
> + struct inode *parent)
> {
> - return erofs_iget(sb, ino);
> + int len = parent ? 4 : 2;
> + erofs_nid_t nid;
> +
> + if (*max_len < len) {
> + *max_len = len;
> + return FILEID_INVALID;
> + }
> +
> + nid = EROFS_I(inode)->nid;
> + fh[0] = (u32)(nid >> 32);
> + fh[1] = (u32)(nid & 0xffffffff);
> +
> + if (parent) {
> + nid = EROFS_I(parent)->nid;
> +
> + fh[2] = (u32)(nid >> 32);
> + fh[3] = (u32)(nid & 0xffffffff);
> + }
> +
> + *max_len = len;
> + return parent ? FILEID_INO64_GEN_PARENT : FILEID_INO64_GEN;
> }
>
> static struct dentry *erofs_fh_to_dentry(struct super_block *sb,
> struct fid *fid, int fh_len, int fh_type)
> {
> - return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
> - erofs_nfs_get_inode);
> + erofs_nid_t nid;
> +
> + if ((fh_type != FILEID_INO64_GEN &&
> + fh_type != FILEID_INO64_GEN_PARENT) || fh_len < 2)
> + return NULL;
> +
> + nid = (u64) fid->raw[0] << 32;
> + nid |= (u64) fid->raw[1];
> +
Redundant new line.
> + return d_obtain_alias(erofs_iget(sb, nid));
> }
>
> static struct dentry *erofs_fh_to_parent(struct super_block *sb,
> struct fid *fid, int fh_len, int fh_type)
> {
> - return generic_fh_to_parent(sb, fid, fh_len, fh_type,
> - erofs_nfs_get_inode);
> + erofs_nid_t nid;
> +
> + if (fh_type != FILEID_INO64_GEN_PARENT || fh_len < 4)
> + return NULL;
> +
> + nid = (u64) fid->raw[2] << 32;
> + nid |= (u64) fid->raw[3];
> +
Same here.
Thanks,
Gao Xiang
