[RFC PATCH v2 14/21] fuse-bpf: support FUSE_READDIR

Daniel Rosenberg
2022-11-22T02:19:13Z

fs/fuse/backing.c | 185 ++++++++++++++++++++++++++++++++++++++
fs/fuse/fuse_i.h | 6 ++
fs/fuse/readdir.c | 5 ++
include/uapi/linux/fuse.h | 6 ++
4 files changed, 202 insertions(+)

diff --git a/fs/fuse/backing.c b/fs/fuse/backing.c
index 425815d7f5dc..a15b5c107cfe 100644
--- a/fs/fuse/backing.c
+++ b/fs/fuse/backing.c
@@ -1597,6 +1597,191 @@ int fuse_bpf_unlink(int *out, struct inode *dir, struct dentry *entry)
dir, entry);
}

+struct fuse_read_io {
+ struct fuse_read_in fri;
+ struct fuse_read_out fro;
+};
+
+static int fuse_readdir_initialize_in(struct fuse_args *fa, struct fuse_read_io *frio,
+ struct file *file, struct dir_context *ctx,
+ bool *force_again, bool *allow_force, bool is_continued)
+{
+ struct fuse_file *ff = file->private_data;
+
+ *fa = (struct fuse_args) {
+ .nodeid = ff->nodeid,
+ .opcode = FUSE_READDIR,
+ .in_numargs = 1,
+ .in_args[0] = (struct fuse_in_arg) {
+ .size = sizeof(frio->fri),
+ .value = &frio->fri,
+ },
+ };
+
+ frio->fri = (struct fuse_read_in) {
+ .fh = ff->fh,
+ .offset = ctx->pos,
+ .size = PAGE_SIZE,
+ };
+
+ *force_again = false;
+ *allow_force = true;
+ return 0;
+}
+
+static int fuse_readdir_initialize_out(struct fuse_args *fa, struct fuse_read_io *frio,
+ struct file *file, struct dir_context *ctx,
+ bool *force_again, bool *allow_force, bool is_continued)
+{
+ u8 *page = (u8 *)__get_free_page(GFP_KERNEL);
+
+ if (!page)
+ return -ENOMEM;
+
+ fa->out_argvar = true;
+ fa->out_numargs = 2;
+ fa->out_args[0] = (struct fuse_arg) {
+ .size = sizeof(frio->fro),
+ .value = &frio->fro,
+ };
+ fa->out_args[1] = (struct fuse_arg) {
+ .size = PAGE_SIZE,
+ .value = page,
+ };
+ frio->fro = (struct fuse_read_out) {
+ .again = 0,
+ .offset = 0,
+ };
+
+ return 0;
+}
+
+struct extfuse_ctx {
+ struct dir_context ctx;
+ u8 *addr;
+ size_t offset;
+};
+
+static bool filldir(struct dir_context *ctx, const char *name, int namelen,
+ loff_t offset, u64 ino, unsigned int d_type)
+{
+ struct extfuse_ctx *ec = container_of(ctx, struct extfuse_ctx, ctx);
+ struct fuse_dirent *fd = (struct fuse_dirent *)(ec->addr + ec->offset);
+
+ if (ec->offset + sizeof(struct fuse_dirent) + namelen > PAGE_SIZE)
+ return false;
+
+ *fd = (struct fuse_dirent) {
+ .ino = ino,
+ .off = offset,
+ .namelen = namelen,
+ .type = d_type,
+ };
+
+ memcpy(fd->name, name, namelen);
+ ec->offset += FUSE_DIRENT_SIZE(fd);
+
+ return true;
+}
+
+static int parse_dirfile(char *buf, size_t nbytes, struct dir_context *ctx)
+{
+ while (nbytes >= FUSE_NAME_OFFSET) {
+ struct fuse_dirent *dirent = (struct fuse_dirent *) buf;
+ size_t reclen = FUSE_DIRENT_SIZE(dirent);
+
+ if (!dirent->namelen || dirent->namelen > FUSE_NAME_MAX)
+ return -EIO;
+ if (reclen > nbytes)
+ break;
+ if (memchr(dirent->name, '/', dirent->namelen) != NULL)
+ return -EIO;
+
+ ctx->pos = dirent->off;
+ if (!dir_emit(ctx, dirent->name, dirent->namelen, dirent->ino,
+ dirent->type))
+ break;
+
+ buf += reclen;
+ nbytes -= reclen;
+ }
+
+ return 0;
+}
+
+
+static int fuse_readdir_backing(struct fuse_args *fa, int *out,
+ struct file *file, struct dir_context *ctx,
+ bool *force_again, bool *allow_force, bool is_continued)
+{
+ struct fuse_file *ff = file->private_data;
+ struct file *backing_dir = ff->backing_file;
+ struct fuse_read_out *fro = fa->out_args[0].value;
+ struct extfuse_ctx ec;
+
+ ec = (struct extfuse_ctx) {
+ .ctx.actor = filldir,
+ .ctx.pos = ctx->pos,
+ .addr = fa->out_args[1].value,
+ };
+
+ if (!ec.addr)
+ return -ENOMEM;
+
+ if (!is_continued)
+ backing_dir->f_pos = file->f_pos;
+
+ *out = iterate_dir(backing_dir, &ec.ctx);
+ if (ec.offset == 0)
+ *allow_force = false;
+ fa->out_args[1].size = ec.offset;
+
+ fro->offset = ec.ctx.pos;
+ fro->again = false;
+
+ return *out;
+}
+
+static int fuse_readdir_finalize(struct fuse_args *fa, int *out,
+ struct file *file, struct dir_context *ctx,
+ bool *force_again, bool *allow_force, bool is_continued)
+{
+ struct fuse_read_out *fro = fa->out_args[0].value;
+ struct fuse_file *ff = file->private_data;
+ struct file *backing_dir = ff->backing_file;
+
+ *out = parse_dirfile(fa->out_args[1].value, fa->out_args[1].size, ctx);
+ *force_again = !!fro->again;
+ if (*force_again && !*allow_force)
+ *out = -EINVAL;
+
+ ctx->pos = fro->offset;
+ backing_dir->f_pos = fro->offset;
+
+ free_page((unsigned long)fa->out_args[1].value);
+ return *out;
+}
+
+int fuse_bpf_readdir(int *out, struct inode *inode, struct file *file, struct dir_context *ctx)
+{
+ int ret;
+ bool allow_force;
+ bool force_again = false;
+ bool is_continued = false;
+
+again:
+ ret = fuse_bpf_backing(inode, struct fuse_read_io, out,
+ fuse_readdir_initialize_in, fuse_readdir_initialize_out,
+ fuse_readdir_backing, fuse_readdir_finalize,
+ file, ctx, &force_again, &allow_force, is_continued);
+ if (force_again && *out >= 0) {
+ is_continued = true;
+ goto again;
+ }
+
+ return ret;
+}
+
static int fuse_access_initialize_in(struct fuse_args *fa, struct fuse_access_in *fai,
struct inode *inode, int mask)
{
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 25cedaa9014c..0ea3fb74caab 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1414,6 +1414,7 @@ int fuse_bpf_file_read_iter(ssize_t *out, struct inode *inode, struct kiocb *ioc
int fuse_bpf_file_write_iter(ssize_t *out, struct inode *inode, struct kiocb *iocb, struct iov_iter *from);
int fuse_bpf_file_fallocate(int *out, struct inode *inode, struct file *file, int mode, loff_t offset, loff_t length);
int fuse_bpf_lookup(struct dentry **out, struct inode *dir, struct dentry *entry, unsigned int flags);
+int fuse_bpf_readdir(int *out, struct inode *inode, struct file *file, struct dir_context *ctx);
int fuse_bpf_access(int *out, struct inode *inode, int mask);

#else
@@ -1484,6 +1485,11 @@ static inline int fuse_bpf_lookup(struct dentry **out, struct inode *dir, struct
return 0;
}

+static inline int fuse_bpf_readdir(int *out, struct inode *inode, struct file *file, struct dir_context *ctx)
+{
+ return 0;
+}
+
static inline int fuse_bpf_access(int *out, struct inode *inode, int mask)
{
return 0;
diff --git a/fs/fuse/readdir.c b/fs/fuse/readdir.c
index e8deaacf1832..f32105679057 100644
--- a/fs/fuse/readdir.c
+++ b/fs/fuse/readdir.c
@@ -20,6 +20,8 @@ static bool fuse_use_readdirplus(struct inode *dir, struct dir_context *ctx)

if (!fc->do_readdirplus)
return false;
+ if (fi->nodeid == 0)
+ return false;
if (!fc->readdirplus_auto)
return true;
if (test_and_clear_bit(FUSE_I_ADVISE_RDPLUS, &fi->state))
@@ -582,6 +584,9 @@ int fuse_readdir(struct file *file, struct dir_context *ctx)
if (fuse_is_bad(inode))
return -EIO;

+ if (fuse_bpf_readdir(&err, inode, file, ctx))
+ return err;
+
mutex_lock(&ff->readdir.lock);

err = UNCACHED;
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index e49e5a8e044c..8c13483f240e 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -709,6 +709,12 @@ struct fuse_read_in {
uint32_t padding;
};

+struct fuse_read_out {
+ uint64_t offset;
+ uint32_t again;
+ uint32_t padding;
+};
+
#define FUSE_COMPAT_WRITE_IN_SIZE 24

struct fuse_write_in {
--
2.38.1.584.g0f3c55d4c2-goog