Add storage driver based functions to access headers of storage files
for metadata extraction. Along with this patch a local filesystem and
gluster via libgfapi implementation is provided. The gluster
implementation is based on code of the saferead_lim function.
---
src/storage/storage_backend.h | 7 ++++
src/storage/storage_backend_fs.c | 30 ++++++++++++++++
src/storage/storage_backend_gluster.c | 66 +++++++++++++++++++++++++++++++++++
src/storage/storage_driver.c | 40 +++++++++++++++++++++
src/storage/storage_driver.h | 3 ++
5 files changed, 146 insertions(+)
diff --git a/src/storage/storage_backend.h b/src/storage/storage_backend.h
index fcbb6da..6be5ca7 100644
--- a/src/storage/storage_backend.h
+++ b/src/storage/storage_backend.h
@@ -190,6 +190,12 @@ typedef int
(*virStorageFileBackendStat)(virStorageSourcePtr src,
struct stat *st);
+typedef ssize_t
+(*virStorageFileBackendReadHeader)(virStorageSourcePtr src,
+ ssize_t max_len,
+ char **buf);
+
+
virStorageFileBackendPtr virStorageFileBackendForType(int type, int protocol);
@@ -204,6 +210,7 @@ struct _virStorageFileBackend {
* error on failure. */
virStorageFileBackendInit backendInit;
virStorageFileBackendDeinit backendDeinit;
+ virStorageFileBackendReadHeader storageFileReadHeader;
/* The following group of callbacks is expected to set errno
* and return -1 on error. No libvirt error shall be reported */
diff --git a/src/storage/storage_backend_fs.c b/src/storage/storage_backend_fs.c
index 3d088ba..33551e7 100644
--- a/src/storage/storage_backend_fs.c
+++ b/src/storage/storage_backend_fs.c
@@ -1375,6 +1375,34 @@ virStorageFileBackendFileStat(virStorageSourcePtr src,
}
+static ssize_t
+virStorageFileBackendFileReadHeader(virStorageSourcePtr src,
+ ssize_t max_len,
+ char **buf)
+{
+ int fd = -1;
+ ssize_t ret = -1;
+
+ if ((fd = virFileOpenAs(src->path, O_RDONLY, 0,
+ src->drv->uid, src->drv->gid, 0)) < 0) {
+ virReportSystemError(-fd, _("Failed to open file '%s'"),
+ src->path);
+ return -1;
+ }
+
+ if ((ret = virFileReadHeaderFD(fd, max_len, buf)) < 0) {
+ virReportSystemError(errno,
+ _("cannot read header '%s'"), src->path);
+ goto cleanup;
+ }
+
+ cleanup:
+ VIR_FORCE_CLOSE(fd);
+
+ return ret;
+}
+
+
virStorageFileBackend virStorageFileBackendFile = {
.type = VIR_STORAGE_TYPE_FILE,
@@ -1383,6 +1411,7 @@ virStorageFileBackend virStorageFileBackendFile = {
.storageFileUnlink = virStorageFileBackendFileUnlink,
.storageFileStat = virStorageFileBackendFileStat,
+ .storageFileReadHeader = virStorageFileBackendFileReadHeader,
};
@@ -1393,6 +1422,7 @@ virStorageFileBackend virStorageFileBackendBlock = {
.backendDeinit = virStorageFileBackendFileDeinit,
.storageFileStat = virStorageFileBackendFileStat,
+ .storageFileReadHeader = virStorageFileBackendFileReadHeader,
};
diff --git a/src/storage/storage_backend_gluster.c b/src/storage/storage_backend_gluster.c
index e578e73..badffae 100644
--- a/src/storage/storage_backend_gluster.c
+++ b/src/storage/storage_backend_gluster.c
@@ -638,6 +638,71 @@ virStorageFileBackendGlusterStat(virStorageSourcePtr src,
}
+static ssize_t
+virStorageFileBackendGlusterReadHeader(virStorageSourcePtr src,
+ ssize_t max_len,
+ char **buf)
+{
+ virStorageFileBackendGlusterPrivPtr priv = src->drv->priv;
+ glfs_fd_t *fd = NULL;
+ size_t alloc = 0;
+ size_t size = 0;
+ int save_errno;
+ ssize_t ret = -1;
+
+ *buf = NULL;
+
+ if (!(fd = glfs_open(priv->vol, src->path, O_RDONLY))) {
+ virReportSystemError(errno, _("Failed to open file '%s'"),
+ src->path);
+ goto cleanup;
+ }
+
+ /* code below is shamelesly stolen from saferead_lim */
+ for (;;) {
+ int count;
+ int requested;
+
+ if (size + BUFSIZ + 1 > alloc) {
+ alloc += alloc / 2;
+ if (alloc < size + BUFSIZ + 1)
+ alloc = size + BUFSIZ + 1;
+
+ if (VIR_REALLOC_N(*buf, alloc) < 0) {
+ save_errno = errno;
+ break;
+ }
+ }
+
+ /* Ensure that (size + requested <= max_len); */
+ requested = MIN(size < max_len ? max_len - size : 0,
+ alloc - size - 1);
+ count = glfs_read(fd, *buf + size, requested, 0);
+ size += count;
+
+ if (count != requested || requested == 0) {
+ save_errno = errno;
+ if (count < 0) {
+ virReportSystemError(errno,
+ _("cannot read header '%s'"), src->path);
+ break;
+ }
+ ret = size;
+ goto cleanup;
+ }
+ }
+
+ VIR_FREE(*buf);
+ errno = save_errno;
+
+ cleanup:
+ if (fd)
+ glfs_close(fd);
+
+ return ret;
+}
+
+
virStorageFileBackend virStorageFileBackendGluster = {
.type = VIR_STORAGE_TYPE_NETWORK,
.protocol = VIR_STORAGE_NET_PROTOCOL_GLUSTER,
@@ -647,4 +712,5 @@ virStorageFileBackend virStorageFileBackendGluster = {
.storageFileUnlink = virStorageFileBackendGlusterUnlink,
.storageFileStat = virStorageFileBackendGlusterStat,
+ .storageFileReadHeader = virStorageFileBackendGlusterReadHeader,
};
diff --git a/src/storage/storage_driver.c b/src/storage/storage_driver.c
index 5e740f9..3019531 100644
--- a/src/storage/storage_driver.c
+++ b/src/storage/storage_driver.c
@@ -2947,3 +2947,43 @@ virStorageFileStat(virStorageSourcePtr src,
return ret;
}
+
+
+/**
+ * virStorageFileReadHeader: read the beginning bytes of a file into a buffer
+ *
+ * @src: file structure pointing to the file
+ * @max_len: maximum number of bytes read from the storage file
+ * @buf: buffer to read the data into. buffer shall be freed by caller)
+ *
+ * Returns the count of bytes read on success and -1 on failure, -2 if the
+ * function isn't supported by the backend. Libvirt error is reported on failure.
+ */
+ssize_t
+virStorageFileReadHeader(virStorageSourcePtr src,
+ ssize_t max_len,
+ char **buf)
+{
+ ssize_t ret;
+
+ if (!virStorageFileIsInitialized(src)) {
+ virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+ _("storage file backend not initialized"));
+ return -1;
+ }
+
+ if (!src->drv->backend->storageFileReadHeader) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("storage file header reading is not supported for "
+ "storage type %s (protocol: %s)'"),
+ virStorageTypeToString(src->type),
+ virStorageNetProtocolTypeToString(src->protocol));
+ return -1;
+ }
+
+ ret = src->drv->backend->storageFileReadHeader(src, max_len, buf);
+
+ VIR_DEBUG("read of storage header %p: ret=%zd", src, ret);
+
+ return ret;
+}
diff --git a/src/storage/storage_driver.h b/src/storage/storage_driver.h
index 49be999..d67d74b 100644
--- a/src/storage/storage_driver.h
+++ b/src/storage/storage_driver.h
@@ -38,6 +38,9 @@ int virStorageFileCreate(virStorageSourcePtr src);
int virStorageFileUnlink(virStorageSourcePtr src);
int virStorageFileStat(virStorageSourcePtr src,
struct stat *stat);
+ssize_t virStorageFileReadHeader(virStorageSourcePtr src,
+ ssize_t max_len,
+ char **buf);
int storageRegister(void);
--
1.9.3
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