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Message-ID: <CAOQ4uxh++mVfJXpPt0UH2Xf87Y9qwhJvtTAU=bXvZk0yR0QUEQ@mail.gmail.com>
Date: Tue, 16 Dec 2025 12:01:58 +0100
From: Amir Goldstein <amir73il@...il.com>
To: Luis Henriques <luis@...lia.com>
Cc: Miklos Szeredi <miklos@...redi.hu>, "Darrick J. Wong" <djwong@...nel.org>,
Bernd Schubert <bschubert@....com>, Kevin Chen <kchen@....com>,
Horst Birthelmer <hbirthelmer@....com>, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, Matt Harvey <mharvey@...ptrading.com>,
kernel-dev@...lia.com
Subject: Re: [RFC PATCH v2 6/6] fuse: implementation of export_operations with FUSE_LOOKUP_HANDLE
On Fri, Dec 12, 2025 at 7:13 PM Luis Henriques <luis@...lia.com> wrote:
>
> This patch allows the NFS handle to use the new file handle provided by the
> LOOKUP_HANDLE operation. It still allows the usage of nodeid+generation as
> an handle if this operation is not supported by the FUSE server or if no
> handle is available for a specific inode. I.e. it can mix both file handle
> types FILEID_INO64_GEN{_PARENT} and FILEID_FUSE_WITH{OUT}_PARENT.
Why the mix? I dont get it.
>
> Signed-off-by: Luis Henriques <luis@...lia.com>
> ---
> fs/fuse/export.c | 162 ++++++++++++++++++++++++++++++++++++---
> include/linux/exportfs.h | 7 ++
> 2 files changed, 160 insertions(+), 9 deletions(-)
>
> diff --git a/fs/fuse/export.c b/fs/fuse/export.c
> index 4a9c95fe578e..b40d146a32f2 100644
> --- a/fs/fuse/export.c
> +++ b/fs/fuse/export.c
> @@ -3,6 +3,7 @@
> * FUSE NFS export support.
> *
> * Copyright (C) 2001-2008 Miklos Szeredi <miklos@...redi.hu>
> + * Copyright (C) 2025 Jump Trading LLC, author: Luis Henriques <luis@...lia.com>
> */
>
> #include "fuse_i.h"
> @@ -10,7 +11,8 @@
>
> struct fuse_inode_handle {
> u64 nodeid;
> - u32 generation;
> + u32 generation; /* XXX change to u64, and use fid->i64.ino in encode/decode? */
> + struct fuse_file_handle fh;
If anything this should be a union
or maybe I don't understand what you were trying to accomplish.
Please try to explain the design better in the commit message.
> };
>
> static struct dentry *fuse_get_dentry(struct super_block *sb,
> @@ -67,8 +69,8 @@ static struct dentry *fuse_get_dentry(struct super_block *sb,
> return ERR_PTR(err);
> }
>
> -static int fuse_encode_fh(struct inode *inode, u32 *fh, int *max_len,
> - struct inode *parent)
> +static int fuse_encode_gen_fh(struct inode *inode, u32 *fh, int *max_len,
> + struct inode *parent)
> {
> int len = parent ? 6 : 3;
> u64 nodeid;
> @@ -96,38 +98,180 @@ static int fuse_encode_fh(struct inode *inode, u32 *fh, int *max_len,
> }
>
> *max_len = len;
> +
> return parent ? FILEID_INO64_GEN_PARENT : FILEID_INO64_GEN;
> }
>
> -static struct dentry *fuse_fh_to_dentry(struct super_block *sb,
> - struct fid *fid, int fh_len, int fh_type)
> +static int fuse_encode_fuse_fh(struct inode *inode, u32 *fh, int *max_len,
> + struct inode *parent)
> +{
> + struct fuse_inode *fi = get_fuse_inode(inode);
> + struct fuse_inode *fip = NULL;
> + struct fuse_inode_handle *handle = (void *)fh;
> + int type = FILEID_FUSE_WITHOUT_PARENT;
> + int len, lenp = 0;
> + int buflen = *max_len << 2; /* max_len: number of words */
> +
> + len = sizeof(struct fuse_inode_handle) + fi->fh->size;
> + if (parent) {
> + fip = get_fuse_inode(parent);
> + if (fip->fh && fip->fh->size) {
> + lenp = sizeof(struct fuse_inode_handle) +
> + fip->fh->size;
> + type = FILEID_FUSE_WITH_PARENT;
> + }
> + }
> +
> + if (buflen < (len + lenp)) {
> + *max_len = (len + lenp) >> 2;
> + return FILEID_INVALID;
> + }
> +
> + handle[0].nodeid = fi->nodeid;
> + handle[0].generation = inode->i_generation;
> + memcpy(&handle[0].fh, fi->fh, len);
> + if (lenp) {
> + handle[1].nodeid = fip->nodeid;
> + handle[1].generation = parent->i_generation;
> + memcpy(&handle[1].fh, fip->fh, lenp);
> + }
> +
> + *max_len = (len + lenp) >> 2;
> +
> + return type;
> +}
> +
> +static int fuse_encode_fh(struct inode *inode, u32 *fh, int *max_len,
> + struct inode *parent)
> +{
> + struct fuse_conn *fc = get_fuse_conn(inode);
> + struct fuse_inode *fi = get_fuse_inode(inode);
> +
> + if (fc->lookup_handle && fi->fh && fi->fh->size)
> + return fuse_encode_fuse_fh(inode, fh, max_len, parent);
> +
> + return fuse_encode_gen_fh(inode, fh, max_len, parent);
> +}
> +
> +static struct dentry *fuse_fh_gen_to_dentry(struct super_block *sb,
> + struct fid *fid, int fh_len)
> {
> struct fuse_inode_handle handle;
>
> - if ((fh_type != FILEID_INO64_GEN &&
> - fh_type != FILEID_INO64_GEN_PARENT) || fh_len < 3)
> + if (fh_len < 3)
I dont understand why this was changed.
> return NULL;
>
> handle.nodeid = (u64) fid->raw[0] << 32;
> handle.nodeid |= (u64) fid->raw[1];
> handle.generation = fid->raw[2];
> +
> return fuse_get_dentry(sb, &handle);
> }
>
> -static struct dentry *fuse_fh_to_parent(struct super_block *sb,
> +static struct dentry *fuse_fh_fuse_to_dentry(struct super_block *sb,
> + struct fid *fid, int fh_len)
> +{
> + struct fuse_inode_handle *handle;
> + struct dentry *dentry;
> + int len = sizeof(struct fuse_file_handle);
> +
> + handle = (void *)fid;
> + len += handle->fh.size;
> +
> + if ((fh_len << 2) < len)
> + return NULL;
> +
> + handle = kzalloc(len, GFP_KERNEL);
> + if (!handle)
> + return NULL;
> +
> + memcpy(handle, fid, len);
> +
> + dentry = fuse_get_dentry(sb, handle);
> + kfree(handle);
> +
> + return dentry;
> +}
> +
> +static struct dentry *fuse_fh_to_dentry(struct super_block *sb,
> struct fid *fid, int fh_len, int fh_type)
> +{
> + switch (fh_type) {
> + case FILEID_INO64_GEN:
> + case FILEID_INO64_GEN_PARENT:
> + return fuse_fh_gen_to_dentry(sb, fid, fh_len);
> + case FILEID_FUSE_WITHOUT_PARENT:
> + case FILEID_FUSE_WITH_PARENT:
> + return fuse_fh_fuse_to_dentry(sb, fid, fh_len);
> + }
> +
> + return NULL;
> +
> +}
> +
> +static struct dentry *fuse_fh_gen_to_parent(struct super_block *sb,
> + struct fid *fid, int fh_len)
> {
> struct fuse_inode_handle parent;
>
> - if (fh_type != FILEID_INO64_GEN_PARENT || fh_len < 6)
> + if (fh_len < 6)
> return NULL;
>
> parent.nodeid = (u64) fid->raw[3] << 32;
> parent.nodeid |= (u64) fid->raw[4];
> parent.generation = fid->raw[5];
> +
> return fuse_get_dentry(sb, &parent);
> }
>
> +static struct dentry *fuse_fh_fuse_to_parent(struct super_block *sb,
> + struct fid *fid, int fh_len)
> +{
> + struct fuse_inode_handle *handle;
> + struct dentry *dentry;
> + int total_len;
> + int len;
> +
> + handle = (void *)fid;
> + total_len = len = sizeof(struct fuse_inode_handle) + handle->fh.size;
> +
> + if ((fh_len << 2) < total_len)
> + return NULL;
> +
> + handle = (void *)(fid + len);
> + len = sizeof(struct fuse_file_handle) + handle->fh.size;
> + total_len += len;
> +
> + if ((fh_len << 2) < total_len)
> + return NULL;
> +
> + handle = kzalloc(len, GFP_KERNEL);
> + if (!handle)
> + return NULL;
> +
> + memcpy(handle, fid, len);
> +
> + dentry = fuse_get_dentry(sb, handle);
> + kfree(handle);
> +
> + return dentry;
> +}
> +
> +static struct dentry *fuse_fh_to_parent(struct super_block *sb,
> + struct fid *fid, int fh_len, int fh_type)
> +{
> + switch (fh_type) {
> + case FILEID_INO64_GEN:
> + case FILEID_INO64_GEN_PARENT:
> + return fuse_fh_gen_to_parent(sb, fid, fh_len);
> + case FILEID_FUSE_WITHOUT_PARENT:
> + case FILEID_FUSE_WITH_PARENT:
> + return fuse_fh_fuse_to_parent(sb, fid, fh_len);
> + }
> +
> + return NULL;
> +}
> +
> static struct dentry *fuse_get_parent(struct dentry *child)
> {
> struct inode *child_inode = d_inode(child);
> diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
> index f0cf2714ec52..db783f6b28bc 100644
> --- a/include/linux/exportfs.h
> +++ b/include/linux/exportfs.h
> @@ -110,6 +110,13 @@ enum fid_type {
> */
> FILEID_INO64_GEN_PARENT = 0x82,
>
> + /*
> + * 64 bit nodeid number, 32 bit generation number,
> + * variable length handle.
> + */
> + FILEID_FUSE_WITHOUT_PARENT = 0x91,
> + FILEID_FUSE_WITH_PARENT = 0x92,
> +
Do we even need a handle with inode+gen+server specific handle?
I didn't think we would. If we do, please explain why.
Thanks,
Amir.
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