Re: [libvirt] [PATCH 4/6] storage: Make virStorageFileReadHeader more universal

Allow specifying offset to read an arbitrary position in the file. This warrants a rename to virStorageFileRead. --- src/qemu/qemu_driver.c | 3 +-- src/storage/storage_backend.h | 9 +++++---- src/storage/storage_backend_fs.c | 20 +++++++++++++------ src/storage/storage_backend_gluster.c | 37 ++++++++++++++++++++++------------- src/storage/storage_source.c | 30 +++++++++++++++------------- src/storage/storage_source.h | 7 ++++--- 6 files changed, 63 insertions(+), 43 deletions(-)

diff --git a/src/storage/storage_backend_gluster.c b/src/storage/storage_backend_gluster.c index 93dce4042..8ea7e603c 100644 --- a/src/storage/storage_backend_gluster.c +++ b/src/storage/storage_backend_gluster.c @@ -151,20 +151,20 @@ virStorageBackendGlusterOpen(virStoragePoolObjPtr pool) static ssize_t -virStorageBackendGlusterReadHeader(glfs_fd_t *fd, - const char *name, - ssize_t maxlen, - char **buf) +virStorageBackendGlusterRead(glfs_fd_t *fd, + const char *name, + size_t len, + char **buf) { char *s; size_t nread = 0; - if (VIR_ALLOC_N(*buf, maxlen) < 0) + if (VIR_ALLOC_N(*buf, len) < 0) return -1; s = *buf; - while (maxlen) { - ssize_t r = glfs_read(fd, s, maxlen, 0); + while (len) { + ssize_t r = glfs_read(fd, s, len, 0); if (r < 0 && errno == EINTR) continue; if (r < 0) { @@ -175,7 +175,7 @@ virStorageBackendGlusterReadHeader(glfs_fd_t *fd, if (r == 0) return nread; s += r; - maxlen -= r; + len -= r; nread += r; } return nread; @@ -292,7 +292,7 @@ virStorageBackendGlusterRefreshVol(virStorageBackendGlusterStatePtr state, goto cleanup; }

- if ((len = virStorageBackendGlusterReadHeader(fd, name, len, &header)) < 0) + if ((len = virStorageBackendGlusterRead(fd, name, len, &header)) < 0) goto cleanup; if (!(meta = virStorageFileGetMetadataFromBuf(name, header, len, @@ -721,9 +721,10 @@ virStorageFileBackendGlusterStat(virStorageSourcePtr src, static ssize_t -virStorageFileBackendGlusterReadHeader(virStorageSourcePtr src, - ssize_t max_len, - char **buf) +virStorageFileBackendGlusterRead(virStorageSourcePtr src, + size_t offset, + size_t len, + char **buf) { virStorageFileBackendGlusterPrivPtr priv = src->drv->priv; glfs_fd_t *fd = NULL; @@ -737,8 +738,16 @@ virStorageFileBackendGlusterReadHeader(virStorageSourcePtr src, return -1; } - ret = virStorageBackendGlusterReadHeader(fd, src->path, max_len, buf); + if (offset > 0) { + if (glfs_lseek(fd, offset, SEEK_SET) == (off_t) -1) { + virReportSystemError(errno, _("cannot seek into '%s'"), src->path); + goto cleanup; + } + } + + ret = virStorageBackendGlusterRead(fd, src->path, len, buf); + cleanup: if (fd) glfs_close(fd); @@ -851,7 +860,7 @@ virStorageFileBackend virStorageFileBackendGluster = { .storageFileCreate = virStorageFileBackendGlusterCreate, .storageFileUnlink = virStorageFileBackendGlusterUnlink, .storageFileStat = virStorageFileBackendGlusterStat, - .storageFileReadHeader = virStorageFileBackendGlusterReadHeader, + .storageFileRead = virStorageFileBackendGlusterRead, .storageFileAccess = virStorageFileBackendGlusterAccess, .storageFileChown = virStorageFileBackendGlusterChown, diff --git a/src/storage/storage_source.c b/src/storage/storage_source.c index c91d629c8..130c2d2f3 100644 --- a/src/storage/storage_source.c +++ b/src/storage/storage_source.c @@ -64,7 +64,7 @@ virStorageFileSupportsBackingChainTraversal(virStorageSourcePtr src) } return backend->storageFileGetUniqueIdentifier && - backend->storageFileReadHeader && + backend->storageFileRead && backend->storageFileAccess; } @@ -263,10 +263,11 @@ virStorageFileStat(virStorageSourcePtr src, /** - * virStorageFileReadHeader: read the beginning bytes of a file into a buffer + * virStorageFileRead: 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 + * @offset: number of bytes to skip in the storage file + * @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 @@ -274,9 +275,10 @@ virStorageFileStat(virStorageSourcePtr src, * Libvirt error is reported on failure. */ ssize_t -virStorageFileReadHeader(virStorageSourcePtr src, - ssize_t max_len, - char **buf) +virStorageFileRead(virStorageSourcePtr src, + size_t offset, + size_t len, + char **buf) { ssize_t ret; @@ -286,18 +288,18 @@ virStorageFileReadHeader(virStorageSourcePtr src, return -1; } - if (!src->drv->backend->storageFileReadHeader) { + if (!src->drv->backend->storageFileRead) { virReportError(VIR_ERR_INTERNAL_ERROR, - _("storage file header reading is not supported for " + _("storage file reading is not supported for " "storage type %s (protocol: %s)"), virStorageTypeToString(src->type), virStorageNetProtocolTypeToString(src->protocol)); return -2; } - ret = src->drv->backend->storageFileReadHeader(src, max_len, buf); + ret = src->drv->backend->storageFileRead(src, offset, len, buf); - VIR_DEBUG("read of storage header %p: ret=%zd", src, ret); + VIR_DEBUG("read of storage %p: ret=%zd", src, ret);