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storage: always probe type with buffer

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This gets rid of another stat() per volume, as well as cutting
bytes read in half, when populating the volumes of a directory
pool during a pool refresh.  Not to mention that it provides an
interface that can let gluster pools also probe file types.

* src/util/virstoragefile.h (virStorageFileProbeFormatFromFD):
Delete.
(virStorageFileProbeFormatFromBuf): New prototype.
(VIR_STORAGE_MAX_HEADER): New constant, based on...
* src/util/virstoragefile.c (STORAGE_MAX_HEAD): ...old name.
(vmdk4GetBackingStore, virStorageFileGetMetadataInternal)
(virStorageFileProbeFormat): Adjust clients.
(virStorageFileProbeFormatFromFD): Delete.
(virStorageFileProbeFormatFromBuf): Export.
* src/storage/storage_backend_fs.c (virStorageBackendProbeTarget):
Adjust client.
* src/libvirt_private.syms (virstoragefile.h): Adjust exports.

Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Eric Blake 2013-11-05 14:12:02 -07:00
parent 3ead2e7ded
commit 348b4e254b
4 changed files with 80 additions and 85 deletions
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2
src/libvirt_private.syms
View File

@ -1731,7 +1731,7 @@ virStorageFileIsClusterFS;
virStorageFileIsSharedFS;
virStorageFileIsSharedFSType;
virStorageFileProbeFormat;
virStorageFileProbeFormatFromFD;
virStorageFileProbeFormatFromBuf;
virStorageFileResize;

52
src/storage/storage_backend_fs.c
View File

@ -1,7 +1,7 @@
/*
* storage_backend_fs.c: storage backend for FS and directory handling
*
* Copyright (C) 2007-2012 Red Hat, Inc.
* Copyright (C) 2007-2013 Red Hat, Inc.
* Copyright (C) 2007-2008 Daniel P. Berrange
*
* This library is free software; you can redistribute it and/or
@ -71,6 +71,8 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
int ret = -1;
virStorageFileMetadata *meta = NULL;
struct stat sb;
char *header = NULL;
ssize_t len = VIR_STORAGE_MAX_HEADER;
*backingStore = NULL;
*backingStoreFormat = VIR_STORAGE_FILE_AUTO;
@ -88,20 +90,33 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
goto error;
}
if ((target->format = virStorageFileProbeFormatFromFD(target->path, fd)) < 0) {
ret = -1;
goto error;
}
if (S_ISDIR(sb.st_mode)) {
target->format = VIR_STORAGE_FILE_DIR;
} else {
if ((len = virFileReadHeaderFD(fd, len, &header)) < 0) {
virReportSystemError(errno, _("cannot read header '%s'"),
target->path);
goto error;
}
if (!(meta = virStorageFileGetMetadataFromFD(target->path, fd,
target->format))) {
ret = -1;
goto error;
target->format = virStorageFileProbeFormatFromBuf(target->path,
header, len);
if (target->format < 0) {
ret = -1;
goto error;
}
if (!(meta = virStorageFileGetMetadataFromBuf(target->path,
header, len,
target->format))) {
ret = -1;
goto error;
}
}
VIR_FORCE_CLOSE(fd);
if (meta->backingStore) {
if (meta && meta->backingStore) {
*backingStore = meta->backingStore;
meta->backingStore = NULL;
if (meta->backingStoreFormat == VIR_STORAGE_FILE_AUTO &&
@ -126,10 +141,10 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
ret = 0;
}
if (capacity && meta->capacity)
if (capacity && meta && meta->capacity)
*capacity = meta->capacity;
if (encryption != NULL && meta->encrypted) {
if (encryption && meta && meta->encrypted) {
if (VIR_ALLOC(*encryption) < 0)
goto cleanup;
@ -150,24 +165,25 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
}
virBitmapFree(target->features);
target->features = meta->features;
meta->features = NULL;
if (meta) {
target->features = meta->features;
meta->features = NULL;
}
if (meta->compat) {
if (meta && meta->compat) {
VIR_FREE(target->compat);
target->compat = meta->compat;
meta->compat = NULL;
}
virStorageFileFreeMetadata(meta);
return ret;
goto cleanup;
error:
VIR_FORCE_CLOSE(fd);
cleanup:
virStorageFileFreeMetadata(meta);
VIR_FREE(header);
return ret;
}

99
src/util/virstoragefile.c
View File

@ -148,11 +148,6 @@ qedGetBackingStore(char **, int *, const char *, size_t);
#define QED_F_BACKING_FILE 0x01
#define QED_F_BACKING_FORMAT_NO_PROBE 0x04
/* VMDK needs at least 20*512 B to find backing store,
* ISO has 5 Byte magic on offset 32769,
* other formats need less */
#define STORAGE_MAX_HEAD 32769+5
static struct FileTypeInfo const fileTypeInfo[] = {
[VIR_STORAGE_FILE_NONE] = { 0, NULL, NULL, LV_LITTLE_ENDIAN,
@ -442,7 +437,7 @@ vmdk4GetBackingStore(char **res,
size_t len;
int ret = BACKING_STORE_ERROR;
if (VIR_ALLOC_N(desc, STORAGE_MAX_HEAD + 1) < 0)
if (VIR_ALLOC_N(desc, VIR_STORAGE_MAX_HEADER) < 0)
goto cleanup;
*res = NULL;
@ -460,8 +455,8 @@ vmdk4GetBackingStore(char **res,
goto cleanup;
}
len = buf_size - 0x200;
if (len > STORAGE_MAX_HEAD)
len = STORAGE_MAX_HEAD;
if (len > VIR_STORAGE_MAX_HEADER)
len = VIR_STORAGE_MAX_HEADER;
memcpy(desc, buf + 0x200, len);
desc[len] = '\0';
start = strstr(desc, prefix);
@ -682,7 +677,7 @@ virBackingStoreIsFile(const char *backing)
return true;
}
static int
int
virStorageFileProbeFormatFromBuf(const char *path,
char *buf,
size_t buflen)
@ -690,7 +685,7 @@ virStorageFileProbeFormatFromBuf(const char *path,
int format = VIR_STORAGE_FILE_RAW;
size_t i;
int possibleFormat = VIR_STORAGE_FILE_RAW;
VIR_DEBUG("path=%s", path);
VIR_DEBUG("path=%s, buf=%p, buflen=%zu", path, buf, buflen);
/* First check file magic */
for (i = 0; i < VIR_STORAGE_FILE_LAST; i++) {
@ -881,57 +876,6 @@ cleanup:
}
/**
* virStorageFileProbeFormatFromFD:
*
* Probe for the format of 'fd' (which is an open file descriptor
* pointing to 'path'), returning the detected disk format.
*
* Callers are advised never to trust the returned 'format'
* unless it is listed as VIR_STORAGE_FILE_RAW, since a
* malicious guest can turn a file into any other non-raw
* format at will.
*
* Best option: Don't use this function
*/
int
virStorageFileProbeFormatFromFD(const char *path, int fd)
{
char *head = NULL;
ssize_t len = STORAGE_MAX_HEAD;
int ret = -1;
struct stat sb;
if (fstat(fd, &sb) < 0) {
virReportSystemError(errno,
_("cannot stat file '%s'"),
path);
return -1;
}
/* No header to probe for directories */
if (S_ISDIR(sb.st_mode)) {
return VIR_STORAGE_FILE_DIR;
}
if (lseek(fd, 0, SEEK_SET) == (off_t)-1) {
virReportSystemError(errno, _("cannot set to start of '%s'"), path);
goto cleanup;
}
if ((len = virFileReadHeaderFD(fd, len, &head)) < 0) {
virReportSystemError(errno, _("cannot read header '%s'"), path);
goto cleanup;
}
ret = virStorageFileProbeFormatFromBuf(path, head, len);
cleanup:
VIR_FREE(head);
return ret;
}
/**
* virStorageFileProbeFormat:
*
@ -948,15 +892,42 @@ cleanup:
int
virStorageFileProbeFormat(const char *path, uid_t uid, gid_t gid)
{
int fd, ret;
int fd;
int ret = -1;
struct stat sb;
ssize_t len = VIR_STORAGE_MAX_HEADER;
char *header = NULL;
if ((fd = virFileOpenAs(path, O_RDONLY, 0, uid, gid, 0)) < 0) {
virReportSystemError(-fd, _("Failed to open file '%s'"), path);
return -1;
}
ret = virStorageFileProbeFormatFromFD(path, fd);
if (fstat(fd, &sb) < 0) {
virReportSystemError(errno, _("cannot stat file '%s'"), path);
goto cleanup;
}
/* No header to probe for directories */
if (S_ISDIR(sb.st_mode)) {
ret = VIR_STORAGE_FILE_DIR;
goto cleanup;
}
if (lseek(fd, 0, SEEK_SET) == (off_t)-1) {
virReportSystemError(errno, _("cannot set to start of '%s'"), path);
goto cleanup;
}
if ((len = virFileReadHeaderFD(fd, len, &header)) < 0) {
virReportSystemError(errno, _("cannot read header '%s'"), path);
goto cleanup;
}
ret = virStorageFileProbeFormatFromBuf(path, header, len);
cleanup:
VIR_FREE(header);
VIR_FORCE_CLOSE(fd);
return ret;
@ -1003,7 +974,7 @@ virStorageFileGetMetadataFromFDInternal(const char *path,
int format)
{
char *buf = NULL;
ssize_t len = STORAGE_MAX_HEAD;
ssize_t len = VIR_STORAGE_MAX_HEADER;
struct stat sb;
virStorageFileMetadataPtr ret = NULL;

12
src/util/virstoragefile.h
View File

@ -27,6 +27,14 @@
# include "virbitmap.h"
# include "virutil.h"
/* Minimum header size required to probe all known formats with
* virStorageFileProbeFormat, or obtain metadata from a known format.
* Rounded to multiple of 512 (ISO has a 5-byte magic at offset
* 32769). Some formats can be probed with fewer bytes. Although
* some formats theoretically permit metadata that can rely on offsets
* beyond this size, in practice that doesn't matter. */
# define VIR_STORAGE_MAX_HEADER 0x8200
enum virStorageFileFormat {
VIR_STORAGE_FILE_AUTO_SAFE = -2,
VIR_STORAGE_FILE_AUTO = -1,
@ -80,8 +88,8 @@ struct _virStorageFileMetadata {
# endif
int virStorageFileProbeFormat(const char *path, uid_t uid, gid_t gid);
int virStorageFileProbeFormatFromFD(const char *path,
int fd);
int virStorageFileProbeFormatFromBuf(const char *path, char *buf,
size_t buflen);
virStorageFileMetadataPtr virStorageFileGetMetadata(const char *path,
int format,