[PATCH v3 2/2] erofs-utils: add NBD-backed OCI image mounting
ChengyuZhu6
hudson at cyzhu.com
Wed Sep 3 18:29:06 AEST 2025
From: Chengyu Zhu <hudsonzhu at tencent.com>
- Add HTTP range downloads for OCI blobs
- Introduce ocierofs_iostream for virtual file I/O
- Add --oci option for OCI image mounting with NBD backend
New mount.erofs -t erofs.nbd option: --oci=[option] source-image mountpoint
Supported options:
- platform=os/arch (default: linux/amd64)
- layer=N (extract specific layer, default: all layers)
- username/password (basic authentication)
e.g.:
./mount/mount.erofs -t erofs.nbd --oci=platform=linux/amd64 \
quay.io/chengyuzhu6/golang:1.22.8-erofs /tmp/test/
Signed-off-by: Chengyu Zhu <hudsonzhu at tencent.com>
---
lib/liberofs_oci.h | 19 +++-
lib/remotes/oci.c | 242 ++++++++++++++++++++++++++++++++++++++++++++-
mount/Makefile.am | 3 +-
mount/main.c | 236 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 493 insertions(+), 7 deletions(-)
diff --git a/lib/liberofs_oci.h b/lib/liberofs_oci.h
index d119a2b..f35228c 100644
--- a/lib/liberofs_oci.h
+++ b/lib/liberofs_oci.h
@@ -7,7 +7,6 @@
#define __EROFS_OCI_H
#include <stdbool.h>
-
#ifdef __cplusplus
extern "C" {
#endif
@@ -56,7 +55,11 @@ struct ocierofs_ctx {
} img;
};
-int ocierofs_init(struct ocierofs_ctx *ctx, const struct ocierofs_config *config);
+struct ocierofs_iostream {
+ struct ocierofs_ctx *ctx;
+ struct erofs_vfile vf;
+ u64 offset;
+};
/*
* ocierofs_build_trees - Build file trees from an OCI container image
@@ -65,8 +68,16 @@ int ocierofs_init(struct ocierofs_ctx *ctx, const struct ocierofs_config *config
*
* Return: 0 on success, negative errno on failure
*/
-int ocierofs_build_trees(struct erofs_importer *importer,
- const struct ocierofs_config *cfg);
+int ocierofs_build_trees(struct erofs_importer *importer, const struct ocierofs_config *cfg);
+
+int ocierofs_is_erofs_native_image(struct ocierofs_ctx *ctx);
+
+int ocierofs_init(struct ocierofs_ctx *ctx, const struct ocierofs_config *config);
+
+void ocierofs_ctx_cleanup(struct ocierofs_ctx *ctx);
+
+int ocierofs_iostream_open(struct ocierofs_iostream *oci_iostream, struct ocierofs_ctx *oci_ctx);
+void ocierofs_iostream_close(struct ocierofs_iostream *oci_iostream);
#ifdef __cplusplus
}
diff --git a/lib/remotes/oci.c b/lib/remotes/oci.c
index 01f1e24..8750772 100644
--- a/lib/remotes/oci.c
+++ b/lib/remotes/oci.c
@@ -33,6 +33,9 @@
#define OCI_MEDIATYPE_MANIFEST "application/vnd.oci.image.manifest.v1+json"
#define OCI_MEDIATYPE_INDEX "application/vnd.oci.image.index.v1+json"
+/* Erofs Native Layer Media Type */
+#define EROFS_MEDIATYPE "application/vnd.erofs"
+
struct ocierofs_request {
char *url;
struct curl_slist *headers;
@@ -1133,7 +1136,7 @@ out:
return ret;
}
-static void ocierofs_ctx_cleanup(struct ocierofs_ctx *ctx)
+void ocierofs_ctx_cleanup(struct ocierofs_ctx *ctx)
{
if (!ctx)
return;
@@ -1193,3 +1196,240 @@ int ocierofs_build_trees(struct erofs_importer *importer,
ocierofs_ctx_cleanup(&ctx);
return ret;
}
+
+static int ocierofs_download_blob_range(struct ocierofs_ctx *ctx, off_t offset, size_t length,
+ void **out_buf, size_t *out_size)
+{
+ struct ocierofs_request req = {};
+ struct ocierofs_response resp = {};
+ const char *api_registry;
+ char rangehdr[64];
+ long http_code = 0;
+ int ret;
+ int index = ctx->img.layer_index;
+
+ if (offset < 0)
+ return -EINVAL;
+
+ api_registry = ocierofs_get_api_registry(ctx->img.registry);
+ if (asprintf(&req.url, "https://%s/v2/%s/blobs/%s",
+ api_registry, ctx->img.repository, ctx->img.layers[index]->digest) == -1)
+ return -ENOMEM;
+
+ if (length)
+ snprintf(rangehdr, sizeof(rangehdr), "Range: bytes=%lld-%lld",
+ (long long)offset, (long long)(offset + (off_t)length - 1));
+ else
+ snprintf(rangehdr, sizeof(rangehdr), "Range: bytes=%lld-",
+ (long long)offset);
+
+ if (ctx->net.auth_header && strstr(ctx->net.auth_header, "Bearer"))
+ req.headers = curl_slist_append(req.headers, ctx->net.auth_header);
+ req.headers = curl_slist_append(req.headers, rangehdr);
+
+ curl_easy_reset(ctx->net.curl);
+
+ ret = ocierofs_curl_setup_common_options(ctx->net.curl);
+ if (ret)
+ goto out;
+
+ ret = ocierofs_curl_setup_rq(ctx->net.curl, req.url, OCIEROFS_HTTP_GET,
+ req.headers,
+ ocierofs_write_callback,
+ &resp, NULL, NULL);
+ if (ret)
+ goto out;
+
+ ret = ocierofs_curl_perform(ctx->net.curl, &http_code);
+ if (ret)
+ goto out;
+
+ if (http_code == 206) {
+ *out_buf = resp.data;
+ *out_size = resp.size;
+ resp.data = NULL;
+ ret = 0;
+ } else if (http_code == 200) {
+ if (offset == 0) {
+ *out_buf = resp.data;
+ *out_size = resp.size;
+ resp.data = NULL;
+ ret = 0;
+ } else {
+ if (offset < resp.size) {
+ size_t available = resp.size - offset;
+ size_t copy_size = length ? min_t(size_t, length, available) : available;
+
+ *out_buf = malloc(copy_size);
+ if (!*out_buf) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ memcpy(*out_buf, resp.data + offset, copy_size);
+ *out_size = copy_size;
+ ret = 0;
+ } else {
+ *out_buf = NULL;
+ *out_size = 0;
+ ret = 0;
+ }
+ }
+ } else {
+ erofs_err("HTTP range request failed with code %ld", http_code);
+ ret = -EIO;
+ }
+
+out:
+ if (req.headers)
+ curl_slist_free_all(req.headers);
+ free(req.url);
+ free(resp.data);
+ return ret;
+}
+
+static ssize_t ocierofs_io_pread(struct erofs_vfile *vf, void *buf, size_t len, u64 offset)
+{
+ struct ocierofs_iostream *oci_iostream = *(struct ocierofs_iostream **)vf->payload;
+ void *download_buf = NULL;
+ size_t download_size = 0;
+ ssize_t ret;
+
+ ret = ocierofs_download_blob_range(oci_iostream->ctx, offset, len,
+ &download_buf, &download_size);
+ if (ret < 0) {
+ memset(buf, 0, len);
+ return len;
+ }
+
+ if (download_buf && download_size > 0) {
+ memcpy(buf, download_buf, download_size);
+ free(download_buf);
+ return download_size;
+ }
+
+ return 0;
+}
+
+static ssize_t ocierofs_io_read(struct erofs_vfile *vf, void *buf, size_t len)
+{
+ struct ocierofs_iostream *oci_iostream = *(struct ocierofs_iostream **)vf->payload;
+ ssize_t ret;
+
+ ret = ocierofs_io_pread(vf, buf, len, oci_iostream->offset);
+ if (ret > 0)
+ oci_iostream->offset += ret;
+
+ return ret;
+}
+
+static off_t ocierofs_io_lseek(struct erofs_vfile *vf, u64 offset, int whence)
+{
+ struct ocierofs_iostream *oci_iostream = *(struct ocierofs_iostream **)vf->payload;
+ off_t new_offset;
+ int layer_index = oci_iostream->ctx->img.layer_index;
+
+ switch (whence) {
+ case SEEK_SET:
+ new_offset = offset;
+ break;
+ case SEEK_CUR:
+ new_offset = oci_iostream->offset + offset;
+ break;
+ case SEEK_END:
+ new_offset = oci_iostream->ctx->img.layers[layer_index]->size + offset;
+ break;
+ default:
+ return -1;
+ }
+
+ if (new_offset < 0 || new_offset > oci_iostream->ctx->img.layers[layer_index]->size)
+ return -1;
+
+ oci_iostream->offset = new_offset;
+ return new_offset;
+}
+
+static ssize_t ocierofs_io_sendfile(struct erofs_vfile *vout, struct erofs_vfile *vin,
+ off_t *pos, size_t count)
+{
+ struct ocierofs_iostream *oci_iostream = *(struct ocierofs_iostream **)vin->payload;
+ char *buf = NULL;
+ ssize_t total_written = 0;
+ ssize_t ret = 0;
+
+ buf = malloc(min_t(size_t, count, 32768));
+ if (!buf)
+ return -ENOMEM;
+
+ while (count > 0) {
+ size_t to_read = min_t(size_t, count, 32768);
+ u64 read_offset = pos ? *pos : oci_iostream->offset;
+
+ ret = ocierofs_io_pread(vin, buf, to_read, read_offset);
+ if (ret <= 0) {
+ erofs_err("OCI I/O sendfile: failed to read from OCI: %s",
+ erofs_strerror(ret));
+ memset(buf, 0, to_read);
+ ret = to_read;
+ }
+
+ ssize_t written = write(vout->fd, buf, ret);
+
+ if (written < 0) {
+ erofs_err("OCI I/O sendfile: failed to write to output: %s",
+ strerror(errno));
+ ret = -errno;
+ break;
+ }
+
+ if (written != ret) {
+ erofs_err("OCI I/O sendfile: partial write: %zd != %zd", written, ret);
+ ret = written;
+ }
+
+ total_written += ret;
+ count -= ret;
+ if (pos)
+ *pos += ret;
+ else
+ oci_iostream->offset += ret;
+ }
+
+ free(buf);
+ return count;
+}
+
+static struct erofs_vfops ocierofs_io_vfops = {
+ .pread = ocierofs_io_pread,
+ .read = ocierofs_io_read,
+ .lseek = ocierofs_io_lseek,
+ .sendfile = ocierofs_io_sendfile,
+};
+
+int ocierofs_iostream_open(struct ocierofs_iostream *oci_iostream, struct ocierofs_ctx *oci_ctx)
+{
+
+ memset(oci_iostream, 0, sizeof(*oci_iostream));
+ oci_iostream->ctx = oci_ctx;
+ oci_iostream->vf.ops = &ocierofs_io_vfops;
+ oci_iostream->vf.fd = -1;
+ *(struct ocierofs_iostream **)oci_iostream->vf.payload = oci_iostream;
+
+ return 0;
+}
+
+void ocierofs_iostream_close(struct ocierofs_iostream *oci_iostream)
+{
+ close(oci_iostream->vf.fd);
+}
+
+int ocierofs_is_erofs_native_image(struct ocierofs_ctx *ctx)
+{
+ if (ctx->img.layer_count > 0 && ctx->img.layers[0] &&
+ ctx->img.layers[0]->media_type) {
+ if (strcmp(ctx->img.layers[0]->media_type, EROFS_MEDIATYPE) != 0)
+ return -ENOENT;
+ return 0;
+ }
+ return -ENOENT;
+}
diff --git a/mount/Makefile.am b/mount/Makefile.am
index d93f3f4..7b971f5 100644
--- a/mount/Makefile.am
+++ b/mount/Makefile.am
@@ -9,5 +9,4 @@ mount_erofs_SOURCES = main.c
mount_erofs_CFLAGS = -Wall -I$(top_srcdir)/include
mount_erofs_LDADD = $(top_builddir)/lib/liberofs.la ${libselinux_LIBS} \
${liblz4_LIBS} ${liblzma_LIBS} ${zlib_LIBS} ${libdeflate_LIBS} \
- ${libzstd_LIBS} ${libqpl_LIBS} ${libxxhash_LIBS} ${libnl3_LIBS}
-endif
+ ${libzstd_LIBS} ${libqpl_LIBS} ${libxxhash_LIBS} ${libnl3_LIBS} ${openssl_LIBS}
diff --git a/mount/main.c b/mount/main.c
index 139b532..77c16f5 100644
--- a/mount/main.c
+++ b/mount/main.c
@@ -15,6 +15,7 @@
#include "erofs/err.h"
#include "erofs/io.h"
#include "../lib/liberofs_nbd.h"
+#include "../lib/liberofs_oci.h"
#ifdef HAVE_LINUX_LOOP_H
#include <linux/loop.h>
#else
@@ -34,6 +35,10 @@ struct loop_info {
#include <sys/sysmacros.h>
#endif
+#ifdef OCIEROFS_ENABLED
+static struct ocierofs_config ocicfg;
+#endif
+
enum erofs_backend_drv {
EROFSAUTO,
EROFSLOCAL,
@@ -56,6 +61,11 @@ static struct erofsmount_cfg {
long flags;
enum erofs_backend_drv backend;
enum erofsmount_mode mountmode;
+ bool umount;
+#ifdef OCIEROFS_ENABLED
+ char *oci_options;
+ bool use_oci;
+#endif
} mountcfg = {
.full_options = "ro",
.flags = MS_RDONLY, /* default mountflags */
@@ -128,6 +138,9 @@ static int erofsmount_parse_options(int argc, char **argv)
static const struct option long_options[] = {
{"help", no_argument, 0, 'h'},
{"reattach", no_argument, 0, 512},
+#ifdef OCIEROFS_ENABLED
+ {"oci", optional_argument, 0, 513},
+#endif
{0, 0, 0, 0},
};
char *dot;
@@ -165,6 +178,12 @@ static int erofsmount_parse_options(int argc, char **argv)
case 512:
mountcfg.mountmode = EROFSMOUNT_MODE_REATTACH;
break;
+#ifdef OCIEROFS_ENABLED
+ case 513:
+ mountcfg.oci_options = optarg;
+ mountcfg.use_oci = true;
+ break;
+#endif
default:
return -EINVAL;
}
@@ -198,6 +217,74 @@ static int erofsmount_parse_options(int argc, char **argv)
return 0;
}
+static int mount_parse_oci_options(struct ocierofs_config *oci_cfg, char *options_str)
+{
+ char *opt, *q, *p;
+
+ if (!options_str)
+ return 0;
+
+ opt = options_str;
+ while (opt) {
+ q = strchr(opt, ',');
+ if (q)
+ *q = '\0';
+
+ p = strstr(opt, "platform=");
+ if (p) {
+ p += strlen("platform=");
+ free(oci_cfg->platform);
+ oci_cfg->platform = strdup(p);
+ if (!oci_cfg->platform)
+ return -ENOMEM;
+ opt = q ? q + 1 : NULL;
+ continue;
+ }
+
+ p = strstr(opt, "layer=");
+ if (p) {
+ p += strlen("layer=");
+ oci_cfg->layer_index = atoi(p);
+ if (oci_cfg->layer_index < 0) {
+ erofs_err("invalid layer index %d",
+ oci_cfg->layer_index);
+ return -EINVAL;
+ }
+ opt = q ? q + 1 : NULL;
+ continue;
+ }
+
+ p = strstr(opt, "username=");
+ if (p) {
+ p += strlen("username=");
+ free(oci_cfg->username);
+ oci_cfg->username = strdup(p);
+ if (!oci_cfg->username)
+ return -ENOMEM;
+ opt = q ? q + 1 : NULL;
+ continue;
+ }
+
+ p = strstr(opt, "password=");
+ if (p) {
+ p += strlen("password=");
+ free(oci_cfg->password);
+ oci_cfg->password = strdup(p);
+ if (!oci_cfg->password)
+ return -ENOMEM;
+ opt = q ? q + 1 : NULL;
+ continue;
+ }
+
+ erofs_err("mkfs: invalid --oci value %s", opt);
+ return -EINVAL;
+
+ opt = q ? q + 1 : NULL;
+ }
+
+ return 0;
+}
+
static int erofsmount_fuse(const char *source, const char *mountpoint,
const char *fstype, const char *options)
{
@@ -750,6 +837,122 @@ err_out:
return err < 0 ? err : 0;
}
+/**
+ * erofsmount_startnbd_oci - Start NBD server for OCI image
+ * @nbdfd: NBD device file descriptor
+ * @oci_ctx: OCI client structure (pre-authenticated)
+ * @auth_header: pre-authenticated auth header
+ *
+ * Start an NBD server that serves data from an OCI image layer.
+ * This function reuses the existing erofsmount_nbd_loopfn logic
+ * but uses erofsoci_iostream as the virtual device instead of a local file.
+ * The OCI client should be pre-authenticated to avoid concurrent auth issues.
+ *
+ * Return: 0 on success, negative errno on failure
+ */
+static int erofsmount_startnbd_oci(int nbdfd, struct ocierofs_ctx *oci_ctx)
+{
+ struct erofsmount_nbd_ctx ctx = {};
+ struct ocierofs_iostream *oci_iostream = NULL;
+ uintptr_t retcode;
+ pthread_t th;
+ int err, err2;
+ int blkbits = 12;
+ int index = oci_ctx->img.layer_index;
+ u64 blocks;
+
+ blocks = (oci_ctx->img.layers[index]->size + (1ULL << blkbits) - 1) >> blkbits;
+
+ oci_iostream = malloc(sizeof(struct ocierofs_iostream));
+ if (!oci_iostream)
+ return -ENOMEM;
+
+ err = ocierofs_iostream_open(oci_iostream, oci_ctx);
+ if (err) {
+ free(oci_iostream);
+ return err;
+ }
+
+ ctx.vd = oci_iostream->vf;
+
+ err = erofs_nbd_connect(nbdfd, blkbits, blocks);
+ if (err < 0) {
+ ocierofs_iostream_close(oci_iostream);
+ free(oci_iostream);
+ return err;
+ }
+ ctx.sk.fd = err;
+
+ err = -pthread_create(&th, NULL, erofsmount_nbd_loopfn, &ctx);
+ if (err) {
+ ocierofs_iostream_close(oci_iostream);
+ free(oci_iostream);
+ close(ctx.sk.fd);
+ return err;
+ }
+
+ err = erofs_nbd_do_it(nbdfd);
+ err2 = -pthread_join(th, (void **)&retcode);
+ if (!err2 && retcode) {
+ erofs_err("NBD worker failed with %s",
+ erofs_strerror(retcode));
+ err2 = retcode;
+ }
+
+ ocierofs_iostream_close(oci_iostream);
+ free(oci_iostream);
+
+ return err ?: err2;
+}
+
+static int erofsmount_nbd_oci(struct ocierofs_ctx *ctx, const char *mountpoint,
+ const char *fstype, int flags, const char *options)
+{
+ char nbdpath[32];
+ int num, nbdfd;
+ pid_t pid;
+ long err;
+
+ if (strcmp(fstype, "erofs")) {
+ fprintf(stderr, "unsupported filesystem type `%s`\n", fstype);
+ return -ENODEV;
+ }
+
+ flags |= O_RDONLY;
+
+ num = erofs_nbd_devscan();
+ if (num < 0)
+ return num;
+
+ (void)snprintf(nbdpath, sizeof(nbdpath), "/dev/nbd%d", num);
+ nbdfd = open(nbdpath, O_RDWR);
+ if (nbdfd < 0)
+ return -errno;
+
+ if ((pid = fork()) == 0) {
+ return erofsmount_startnbd_oci(nbdfd, ctx) ?
+ EXIT_FAILURE : EXIT_SUCCESS;
+ }
+ close(nbdfd);
+
+ while (1) {
+ err = erofs_nbd_in_service(num);
+ if (err == -ENOENT || err == -ENOTCONN) {
+ usleep(50000);
+ continue;
+ }
+ if (err >= 0)
+ err = (err != pid ? -EBUSY : 0);
+ break;
+ }
+ if (!err) {
+ err = mount(nbdpath, mountpoint, fstype, flags, options);
+ if (err < 0)
+ err = -errno;
+ }
+ return err;
+}
+
int main(int argc, char *argv[])
{
int err;
@@ -785,9 +988,42 @@ int main(int argc, char *argv[])
}
if (mountcfg.backend == EROFSNBD) {
+#ifdef OCIEROFS_ENABLED
+ if (mountcfg.use_oci) {
+ struct ocierofs_ctx ctx = {};
+
+ ocicfg.image_ref = mountcfg.device;
+ err = mount_parse_oci_options(&ocicfg, mountcfg.oci_options);
+ if (err)
+ goto exit;
+ err = ocierofs_init(&ctx, &ocicfg);
+ if (err) {
+ ocierofs_ctx_cleanup(&ctx);
+ goto exit;
+ }
+
+ err = ocierofs_is_erofs_native_image(&ctx);
+ if (err) {
+ ocierofs_ctx_cleanup(&ctx);
+ goto exit;
+ }
+
+ err = erofsmount_nbd_oci(&ctx, mountcfg.target,
+ mountcfg.fstype, mountcfg.flags, mountcfg.options);
+ if (err) {
+ ocierofs_ctx_cleanup(&ctx);
+ goto exit;
+ }
+ } else {
+ err = erofsmount_nbd(mountcfg.device, mountcfg.target,
+ mountcfg.fstype, mountcfg.flags,
+ mountcfg.options);
+ }
+#else
err = erofsmount_nbd(mountcfg.device, mountcfg.target,
mountcfg.fstype, mountcfg.flags,
mountcfg.options);
+#endif
goto exit;
}
--
2.51.0
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