block: Add tar container format

Tar is a very widely used format to store data in. Sometimes people even put
virtual machine images in there.

So it makes sense for qemu to be able to read from tar files. I implemented a
written from scratch reader that also knows about the GNU sparse format, which
is what pigz creates.

This version checks for filenames that end on well-known extensions. The logic
could be changed to search for filenames given on the command line, but that
would require changes to more parts of qemu.

The tar reader in conjunctiuon with dzip gives us the chance to download
tar'ed up virtual machine images (even via http) and instantly make use of
them.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Bruce Rogers <brogers@novell.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
[TH: Use bdrv_open options instead of filename]
Signed-off-by: Tim Hardeck <thardeck@suse.de>
[AF: bdrv_file_open got an Error **errp argument, bdrv_delete -> brd_unref]
[AF: qemu_opts_create_nofail() -> qemu_opts_create(),
     bdrv_file_open() -> bdrv_open(), based on work by brogers]
[AF: error_is_set() dropped for v2.1.0-rc0]
Signed-off-by: Andreas Färber <afaerber@suse.de>

2 files changed, 387 insertions, 0 deletions

diff --git a/block/Makefile.objs b/block/Makefile.objs
index 080fd26e2..0790d1995 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -25,6 +25,7 @@ common-obj-y += stream.o
 common-obj-y += commit.o
 common-obj-y += backup.o
 common-obj-y += dictzip.o
+common-obj-y += tar.o
 
 iscsi.o-cflags     := $(LIBISCSI_CFLAGS)
 iscsi.o-libs       := $(LIBISCSI_LIBS)
diff --git a/block/tar.c b/block/tar.c
new file mode 100644
index 000000000..2f42d20ab
--- /dev/null
+++ b/block/tar.c
@@ -0,0 +1,386 @@
+/*
+ * Tar block driver
+ *
+ * Copyright (c) 2009 Alexander Graf <agraf@suse.de>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu-common.h"
+#include "block/block_int.h"
+
+// #define DEBUG
+
+#ifdef DEBUG
+#define dprintf(fmt, ...) do { printf("tar: " fmt, ## __VA_ARGS__); } while (0)
+#else
+#define dprintf(fmt, ...) do { } while (0)
+#endif
+
+#define SECTOR_SIZE      512
+
+#define POSIX_TAR_MAGIC  "ustar"
+#define OFFS_LENGTH      0x7c
+#define OFFS_TYPE        0x9c
+#define OFFS_MAGIC       0x101
+
+#define OFFS_S_SP        0x182
+#define OFFS_S_EXT       0x1e2
+#define OFFS_S_LENGTH    0x1e3
+#define OFFS_SX_EXT      0x1f8
+
+typedef struct SparseCache {
+    uint64_t start;
+    uint64_t end;
+} SparseCache;
+
+typedef struct BDRVTarState {
+    BlockDriverState *hd;
+    size_t file_sec;
+    uint64_t file_len;
+    SparseCache *sparse;
+    int sparse_num;
+    uint64_t last_end;
+    char longfile[2048];
+} BDRVTarState;
+
+static int tar_probe(const uint8_t *buf, int buf_size, const char *filename)
+{
+    if (buf_size < OFFS_MAGIC + 5)
+        return 0;
+
+    /* we only support newer tar */
+    if (!strncmp((char*)buf + OFFS_MAGIC, POSIX_TAR_MAGIC, 5))
+        return 100;
+
+    return 0;
+}
+
+static int str_ends(char *str, const char *end)
+{
+    int end_len = strlen(end);
+    int str_len = strlen(str);
+
+    if (str_len < end_len)
+        return 0;
+
+    return !strncmp(str + str_len - end_len, end, end_len);
+}
+
+static int is_target_file(BlockDriverState *bs, char *filename)
+{
+    int retval = 0;
+
+    if (str_ends(filename, ".raw"))
+        retval = 1;
+
+    if (str_ends(filename, ".qcow"))
+        retval = 1;
+
+    if (str_ends(filename, ".qcow2"))
+        retval = 1;
+
+    if (str_ends(filename, ".vmdk"))
+        retval = 1;
+
+    dprintf("does filename %s match? %s\n", filename, retval ? "yes" : "no");
+
+    /* make sure we're not using this name again */
+    filename[0] = '\0';
+    return retval;
+}
+
+static uint64_t tar2u64(char *ptr)
+{
+    uint64_t retval;
+    char oldend = ptr[12];
+
+    ptr[12] = '\0';
+    if (*ptr & 0x80) {
+        /* XXX we only support files up to 64 bit length */
+        retval = be64_to_cpu(*(uint64_t *)(ptr+4));
+        dprintf("Convert %lx -> %#lx\n", *(uint64_t*)(ptr+4), retval);
+    } else {
+        retval = strtol(ptr, NULL, 8);
+        dprintf("Convert %s -> %#lx\n", ptr, retval);
+    }
+
+    ptr[12] = oldend;
+
+    return retval;
+}
+
+static void tar_sparse(BDRVTarState *s, uint64_t offs, uint64_t len)
+{
+    SparseCache *sparse;
+
+    if (!len)
+        return;
+    if (!(offs - s->last_end)) {
+        s->last_end += len;
+        return;
+    }
+    if (s->last_end > offs)
+        return;
+
+    dprintf("Last chunk until %lx new chunk at %lx\n", s->last_end, offs);
+
+    s->sparse = g_realloc(s->sparse, (s->sparse_num + 1) * sizeof(SparseCache));
+    sparse = &s->sparse[s->sparse_num];
+    sparse->start = s->last_end;
+    sparse->end = offs;
+    s->last_end = offs + len;
+    s->sparse_num++;
+    dprintf("Sparse at %lx end=%lx\n", sparse->start,
+                                       sparse->end);
+}
+
+static QemuOptsList runtime_opts = {
+    .name = "tar",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
+    .desc = {
+        {
+            .name = "filename",
+            .type = QEMU_OPT_STRING,
+            .help = "URL to the tar file",
+        },
+        { /* end of list */ }
+    },
+};
+
+static int tar_open(BlockDriverState *bs, QDict *options, int flags, Error **errp)
+{
+    BDRVTarState *s = bs->opaque;
+    char header[SECTOR_SIZE];
+    char *real_file = header;
+    char *magic;
+    size_t header_offs = 0;
+    int ret;
+    QemuOpts *opts;
+    Error *local_err = NULL;
+    const char *filename;
+
+    opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &local_err);
+    if (local_err != NULL) {
+        error_propagate(errp, local_err);
+        ret = -EINVAL;
+        goto fail;
+    }
+
+    filename = qemu_opt_get(opts, "filename");
+
+    if (!strncmp(filename, "tar://", 6))
+        filename += 6;
+    else if (!strncmp(filename, "tar:", 4))
+        filename += 4;
+
+    ret = bdrv_open(&s->hd, filename, NULL, NULL, flags | BDRV_O_PROTOCOL, NULL, &local_err);
+    if (ret < 0) {
+        error_propagate(errp, local_err);
+        qemu_opts_del(opts);
+        return ret;
+    }
+
+    /* Search the file for an image */
+
+    do {
+        /* tar header */
+        if (bdrv_pread(s->hd, header_offs, header, SECTOR_SIZE) != SECTOR_SIZE)
+            goto fail;
+
+        if ((header_offs > 1) && !header[0]) {
+            fprintf(stderr, "Tar: No image file found in archive\n");
+            goto fail;
+        }
+
+        magic = &header[OFFS_MAGIC];
+        if (strncmp(magic, POSIX_TAR_MAGIC, 5)) {
+            fprintf(stderr, "Tar: Invalid magic: %s\n", magic);
+            goto fail;
+        }
+
+        dprintf("file type: %c\n", header[OFFS_TYPE]);
+
+        /* file length*/
+        s->file_len = (tar2u64(&header[OFFS_LENGTH]) + (SECTOR_SIZE - 1)) &
+                      ~(SECTOR_SIZE - 1);
+        s->file_sec = (header_offs / SECTOR_SIZE) + 1;
+
+        header_offs += s->file_len + SECTOR_SIZE;
+
+        if (header[OFFS_TYPE] == 'L') {
+            bdrv_pread(s->hd, header_offs - s->file_len, s->longfile,
+                       sizeof(s->longfile));
+            s->longfile[sizeof(s->longfile)-1] = '\0';
+        } else if (s->longfile[0]) {
+            real_file = s->longfile;
+        } else {
+            real_file = header;
+        }
+    } while(!is_target_file(bs, real_file));
+
+    /* We found an image! */
+
+    if (header[OFFS_TYPE] == 'S') {
+        uint8_t isextended;
+        int i;
+
+        for (i = OFFS_S_SP; i < (OFFS_S_SP + (4 * 24)); i += 24)
+            tar_sparse(s, tar2u64(&header[i]), tar2u64(&header[i+12]));
+
+        s->file_len = tar2u64(&header[OFFS_S_LENGTH]);
+        isextended = header[OFFS_S_EXT];
+
+        while (isextended) {
+            if (bdrv_pread(s->hd, s->file_sec * SECTOR_SIZE, header,
+                           SECTOR_SIZE) != SECTOR_SIZE)
+                goto fail;
+
+            for (i = 0; i < (21 * 24); i += 24)
+                tar_sparse(s, tar2u64(&header[i]), tar2u64(&header[i+12]));
+            isextended = header[OFFS_SX_EXT];
+            s->file_sec++;
+        }
+        tar_sparse(s, s->file_len, 1);
+    }
+    qemu_opts_del(opts);
+
+    return 0;
+
+fail:
+    fprintf(stderr, "Tar: Error opening file\n");
+    bdrv_unref(s->hd);
+    qemu_opts_del(opts);
+    return -EINVAL;
+}
+
+typedef struct TarAIOCB {
+    BlockAIOCB common;
+    QEMUBH *bh;
+} TarAIOCB;
+
+/* This callback gets invoked when we have pure sparseness */
+static void tar_sparse_cb(void *opaque)
+{
+    TarAIOCB *acb = (TarAIOCB *)opaque;
+
+    acb->common.cb(acb->common.opaque, 0);
+    qemu_bh_delete(acb->bh);
+    qemu_aio_unref(acb);
+}
+
+static void tar_aio_cancel(BlockAIOCB *blockacb)
+{
+}
+
+static AIOCBInfo tar_aiocb_info = {
+    .aiocb_size         = sizeof(TarAIOCB),
+    .cancel_async       = tar_aio_cancel,
+};
+
+/* This is where we get a request from a caller to read something */
+static BlockAIOCB *tar_aio_readv(BlockDriverState *bs,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+        BlockCompletionFunc *cb, void *opaque)
+{
+    BDRVTarState *s = bs->opaque;
+    SparseCache *sparse;
+    int64_t sec_file = sector_num + s->file_sec;
+    int64_t start = sector_num * SECTOR_SIZE;
+    int64_t end = start + (nb_sectors * SECTOR_SIZE);
+    int i;
+    TarAIOCB *acb;
+
+    for (i = 0; i < s->sparse_num; i++) {
+        sparse = &s->sparse[i];
+        if (sparse->start > end) {
+            /* We expect the cache to be start increasing */
+            break;
+        } else if ((sparse->start < start) && (sparse->end <= start)) {
+            /* sparse before our offset */
+            sec_file -= (sparse->end - sparse->start) / SECTOR_SIZE;
+        } else if ((sparse->start <= start) && (sparse->end >= end)) {
+            /* all our sectors are sparse */
+            char *buf = g_malloc0(nb_sectors * SECTOR_SIZE);
+
+            acb = qemu_aio_get(&tar_aiocb_info, bs, cb, opaque);
+            qemu_iovec_from_buf(qiov, 0, buf, nb_sectors * SECTOR_SIZE);
+            g_free(buf);
+            acb->bh = qemu_bh_new(tar_sparse_cb, acb);
+            qemu_bh_schedule(acb->bh);
+
+            return &acb->common;
+        } else if (((sparse->start >= start) && (sparse->start < end)) ||
+                   ((sparse->end >= start) && (sparse->end < end))) {
+            /* we're semi-sparse (worst case) */
+            /* let's go synchronous and read all sectors individually */
+            char *buf = g_malloc(nb_sectors * SECTOR_SIZE);
+            uint64_t offs;
+
+            for (offs = 0; offs < (nb_sectors * SECTOR_SIZE);
+                 offs += SECTOR_SIZE) {
+                bdrv_pread(bs, (sector_num * SECTOR_SIZE) + offs,
+                           buf + offs, SECTOR_SIZE);
+            }
+
+            qemu_iovec_from_buf(qiov, 0, buf, nb_sectors * SECTOR_SIZE);
+            acb = qemu_aio_get(&tar_aiocb_info, bs, cb, opaque);
+            acb->bh = qemu_bh_new(tar_sparse_cb, acb);
+            qemu_bh_schedule(acb->bh);
+
+            return &acb->common;
+        }
+    }
+
+    return bdrv_aio_readv(s->hd, sec_file, qiov, nb_sectors,
+                          cb, opaque);
+}
+
+static void tar_close(BlockDriverState *bs)
+{
+    dprintf("Close\n");
+}
+
+static int64_t tar_getlength(BlockDriverState *bs)
+{
+    BDRVTarState *s = bs->opaque;
+    dprintf("getlength -> %ld\n", s->file_len);
+    return s->file_len;
+}
+
+static BlockDriver bdrv_tar = {
+    .format_name     = "tar",
+    .protocol_name   = "tar",
+
+    .instance_size   = sizeof(BDRVTarState),
+    .bdrv_file_open  = tar_open,
+    .bdrv_close      = tar_close,
+    .bdrv_getlength  = tar_getlength,
+    .bdrv_probe      = tar_probe,
+
+    .bdrv_aio_readv  = tar_aio_readv,
+};
+
+static void tar_block_init(void)
+{
+    bdrv_register(&bdrv_tar);
+}
+
+block_init(tar_block_init);