* [RFC PATCH 1/1] fuse: restructure requests extensions handling
2026-03-09 14:59 [RFC PATCH 0/1] fuse: restructure requests extensions handling Luis Henriques
@ 2026-03-09 14:59 ` Luis Henriques
0 siblings, 0 replies; 2+ messages in thread
From: Luis Henriques @ 2026-03-09 14:59 UTC (permalink / raw)
To: Miklos Szeredi
Cc: linux-fsdevel, linux-kernel, Matt Harvey, kernel-dev, Luis Henriques
This commit simplifies the implementation of extensions by using an
extensions vector just like the other (in/out) args.
This simplification includes reverting the handling of security contexts
back into a regular inarg, as it was done before commit 15d937d7ca8c
("fuse: add request extension").
Signed-off-by: Luis Henriques <luis@igalia.com>
---
fs/fuse/dev.c | 35 +++++++++++++++-
fs/fuse/dir.c | 104 +++++++++++++++++++++--------------------------
fs/fuse/fuse_i.h | 11 ++++-
3 files changed, 89 insertions(+), 61 deletions(-)
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 0b0241f47170..5bf5f427a5c6 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -654,8 +654,15 @@ static void fuse_args_to_req(struct fuse_req *req, struct fuse_args *args)
req->in.h.opcode = args->opcode;
req->in.h.nodeid = args->nodeid;
req->args = args;
- if (args->is_ext)
- req->in.h.total_extlen = args->in_args[args->ext_idx].size / 8;
+ if (args->has_ext) {
+ int i;
+
+ req->in.h.total_extlen =
+ sizeof(struct fuse_ext_header) * args->numext;
+ for (i = 0; i < args->numext; i++)
+ req->in.h.total_extlen += args->ext_args[i].size;
+ req->in.h.total_extlen /= 8;
+ }
if (args->end)
__set_bit(FR_ASYNC, &req->flags);
}
@@ -1226,6 +1233,28 @@ int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
return err;
}
+static int fuse_copy_extensions(struct fuse_copy_state *cs,
+ struct fuse_args *args)
+{
+ struct fuse_ext_header xh;
+ struct fuse_ext_arg *arg;
+ int err = 0;
+ int i;
+
+ for (i = 0; !err && i < args->numext; i++) {
+ arg = &args->ext_args[i];
+ xh.size = arg->size;
+ xh.type = arg->type;
+ /* Copy extension header... */
+ err = fuse_copy_one(cs, &xh, sizeof(xh));
+ if (!err)
+ /* ... and payload */
+ err = fuse_copy_one(cs, arg->value, arg->size);
+ }
+
+ return err;
+}
+
static int forget_pending(struct fuse_iqueue *fiq)
{
return fiq->forget_list_head.next != NULL;
@@ -1497,6 +1526,8 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file,
if (!err)
err = fuse_copy_args(cs, args->in_numargs, args->in_pages,
(struct fuse_arg *) args->in_args, 0);
+ if (!err)
+ err = fuse_copy_extensions(cs, args);
fuse_copy_finish(cs);
spin_lock(&fpq->lock);
clear_bit(FR_LOCKED, &req->flags);
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 7ac6b232ef12..97a34de2a3df 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -711,26 +711,6 @@ static int get_security_context(struct dentry *entry, umode_t mode,
return err;
}
-static void *extend_arg(struct fuse_in_arg *buf, u32 bytes)
-{
- void *p;
- u32 newlen = buf->size + bytes;
-
- p = krealloc(buf->value, newlen, GFP_KERNEL);
- if (!p) {
- kfree(buf->value);
- buf->size = 0;
- buf->value = NULL;
- return NULL;
- }
-
- memset(p + buf->size, 0, bytes);
- buf->value = p;
- buf->size = newlen;
-
- return p + newlen - bytes;
-}
-
static u32 fuse_ext_size(size_t size)
{
return FUSE_REC_ALIGN(sizeof(struct fuse_ext_header) + size);
@@ -739,67 +719,77 @@ static u32 fuse_ext_size(size_t size)
/*
* This adds just a single supplementary group that matches the parent's group.
*/
-static int get_create_supp_group(struct mnt_idmap *idmap,
- struct inode *dir,
- struct fuse_in_arg *ext)
+static int fuse_create_supp_group(struct mnt_idmap *idmap, struct inode *dir,
+ struct fuse_args *args)
{
struct fuse_conn *fc = get_fuse_conn(dir);
- struct fuse_ext_header *xh;
+ struct fuse_ext_arg *extarg;
struct fuse_supp_groups *sg;
kgid_t kgid = dir->i_gid;
vfsgid_t vfsgid = make_vfsgid(idmap, fc->user_ns, kgid);
gid_t parent_gid = from_kgid(fc->user_ns, kgid);
-
u32 sg_len = fuse_ext_size(sizeof(*sg) + sizeof(sg->groups[0]));
- if (parent_gid == (gid_t) -1 || vfsgid_eq_kgid(vfsgid, current_fsgid()) ||
+ if (parent_gid == (gid_t) -1 ||
+ vfsgid_eq_kgid(vfsgid, current_fsgid()) ||
!vfsgid_in_group_p(vfsgid))
return 0;
- xh = extend_arg(ext, sg_len);
- if (!xh)
- return -ENOMEM;
-
- xh->size = sg_len;
- xh->type = FUSE_EXT_GROUPS;
+ BUG_ON(args->numext >= ARRAY_SIZE(args->ext_args));
- sg = (struct fuse_supp_groups *) &xh[1];
+ sg = kzalloc(sg_len, GFP_KERNEL);
+ if (!sg)
+ return -ENOMEM;
sg->nr_groups = 1;
sg->groups[0] = parent_gid;
+ extarg = &args->ext_args[args->numext];
+ extarg->type = FUSE_EXT_GROUPS;
+ extarg->size = sg_len;
+ extarg->value = sg;
+ args->numext++;
+
return 0;
}
-static int get_create_ext(struct mnt_idmap *idmap,
- struct fuse_args *args,
- struct inode *dir, struct dentry *dentry,
- umode_t mode)
+static int fuse_create_ext(struct mnt_idmap *idmap, struct fuse_args *args,
+ struct inode *dir, struct dentry *dentry,
+ umode_t mode)
{
struct fuse_conn *fc = get_fuse_conn_super(dentry->d_sb);
- struct fuse_in_arg ext = { .size = 0, .value = NULL };
int err = 0;
- if (fc->init_security)
- err = get_security_context(dentry, mode, &ext);
- if (!err && fc->create_supp_group)
- err = get_create_supp_group(idmap, dir, &ext);
-
- if (!err && ext.size) {
- WARN_ON(args->in_numargs >= ARRAY_SIZE(args->in_args));
- args->is_ext = true;
- args->ext_idx = args->in_numargs++;
- args->in_args[args->ext_idx] = ext;
- } else {
- kfree(ext.value);
+ /* security ctx isn't really an extension */
+ if (fc->init_security) {
+ /* XXX maybe the idx shouldn't be hard-coded...? */
+ WARN_ON(args->in_numargs != 2);
+ args->in_numargs = 3;
+ err = get_security_context(dentry, mode, &args->in_args[2]);
+ if (err)
+ return err;
}
+ if (fc->create_supp_group)
+ err = fuse_create_supp_group(idmap, dir, args);
+
+ if (!err)
+ args->has_ext = true;
+ else if (fc->init_security)
+ kfree(args->in_args[2].value);
return err;
}
-static void free_ext_value(struct fuse_args *args)
+static void fuse_free_ext(struct fuse_conn *fc, struct fuse_args *args)
{
- if (args->is_ext)
- kfree(args->in_args[args->ext_idx].value);
+ int i;
+
+ if (fc->init_security)
+ kfree(args->in_args[2].value);
+
+ for (i = 0; i < args->numext; i++)
+ kfree(args->ext_args[i].value);
+
+ args->has_ext = false;
}
/*
@@ -868,12 +858,12 @@ static int fuse_create_open(struct mnt_idmap *idmap, struct inode *dir,
args.out_args[1].size = sizeof(*outopenp);
args.out_args[1].value = outopenp;
- err = get_create_ext(idmap, &args, dir, entry, mode);
+ err = fuse_create_ext(idmap, &args, dir, entry, mode);
if (err)
goto out_free_ff;
err = fuse_simple_idmap_request(idmap, fm, &args);
- free_ext_value(&args);
+ fuse_free_ext(fm->fc, &args);
if (err)
goto out_free_ff;
@@ -995,13 +985,13 @@ static struct dentry *create_new_entry(struct mnt_idmap *idmap, struct fuse_moun
args->out_args[0].value = &outarg;
if (args->opcode != FUSE_LINK) {
- err = get_create_ext(idmap, args, dir, entry, mode);
+ err = fuse_create_ext(idmap, args, dir, entry, mode);
if (err)
goto out_put_forget_req;
}
err = fuse_simple_idmap_request(idmap, fm, args);
- free_ext_value(args);
+ fuse_free_ext(fm->fc, args);
if (err)
goto out_put_forget_req;
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 7f16049387d1..3bde38feae26 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -326,12 +326,18 @@ struct fuse_folio_desc {
unsigned int offset;
};
+struct fuse_ext_arg {
+ unsigned int type;
+ unsigned int size;
+ void *value;
+};
+
struct fuse_args {
uint64_t nodeid;
uint32_t opcode;
uint8_t in_numargs;
uint8_t out_numargs;
- uint8_t ext_idx;
+ uint8_t numext;
bool force:1;
bool noreply:1;
bool nocreds:1;
@@ -342,10 +348,11 @@ struct fuse_args {
bool page_zeroing:1;
bool page_replace:1;
bool may_block:1;
- bool is_ext:1;
+ bool has_ext:1;
bool is_pinned:1;
bool invalidate_vmap:1;
struct fuse_in_arg in_args[4];
+ struct fuse_ext_arg ext_args[2];
struct fuse_arg out_args[2];
void (*end)(struct fuse_mount *fm, struct fuse_args *args, int error);
/* Used for kvec iter backed by vmalloc address */
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