This function takes a FD and determines whether the current
position is in data section or in a hole. In addition to that,
it also determines how much bytes are there remaining till the
current section ends.
Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
src/libvirt_private.syms | 1 +
src/util/virfile.c | 81 +++++++++++++++++++
src/util/virfile.h | 3 +
tests/virfiletest.c | 203 +++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 288 insertions(+)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 181e178..7132b3a 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1620,6 +1620,7 @@ virFileGetHugepageSize;
virFileGetMountReverseSubtree;
virFileGetMountSubtree;
virFileHasSuffix;
+virFileInData;
virFileIsAbsPath;
virFileIsDir;
virFileIsExecutable;
diff --git a/src/util/virfile.c b/src/util/virfile.c
index cbfa384..093125c 100644
--- a/src/util/virfile.c
+++ b/src/util/virfile.c
@@ -3793,6 +3793,87 @@ virFileComparePaths(const char *p1, const char *p2)
cleanup:
VIR_FREE(res1);
VIR_FREE(res2);
+
+ return ret;
+}
+
+
+int virFileInData(int fd,
+ int *inData,
+ unsigned long long *length)
+{
+ int ret = -1;
+ off_t cur, data, hole, end;
+
+ /* Get current position */
+ cur = lseek(fd, 0, SEEK_CUR);
+ if (cur == (off_t) -1) {
+ virReportSystemError(errno, "%s",
+ _("Unable to get current position in file"));
+ goto cleanup;
+ }
+
+ /* Now try to get data and hole offsets */
+ data = lseek(fd, cur, SEEK_DATA);
+
+ /* There are four options:
+ * 1) data == cur; @cur is in data
+ * 2) data > cur; @cur is in a hole, next data at @data
+ * 3) data < 0, errno = ENXIO; either @cur is in trailing hole, or @cur is beyond EOF.
+ * 4) data < 0, errno != ENXIO; we learned nothing
+ */
+
+ if (data == (off_t) -1) {
+ /* cases 3 and 4 */
+ if (errno != ENXIO) {
+ virReportSystemError(errno, "%s",
+ _("Unable to seek to data"));
+ goto cleanup;
+ }
+
+ *inData = 0;
+ /* There are two situations now. There is always an
+ * implicit hole at EOF. However, there might be a
+ * trailing hole just before EOF too. If that's the case
+ * report it. */
+ if ((end = lseek(fd, 0, SEEK_END)) == (off_t) -1) {
+ virReportSystemError(errno, "%s",
+ _("Unable to seek to EOF"));
+ goto cleanup;
+ }
+ *length = end - cur;
+ } else if (data > cur) {
+ /* case 2 */
+ *inData = 0;
+ *length = data - cur;
+ } else {
+ /* case 1 */
+ *inData = 1;
+
+ /* We don't know where does the next hole start. Let's
+ * find out. Here we get the same 4 possibilities as
+ * described above.*/
+ hole = lseek(fd, data, SEEK_HOLE);
+ if (hole == (off_t) -1 || hole == data) {
+ /* cases 1, 3 and 4 */
+ /* Wait a second. The reason why we are here is
+ * because we are in data. But at the same time we
+ * are in a trailing hole? Wut!? Do the best what we
+ * can do here. */
+ virReportSystemError(errno, "%s",
+ _("unable to seek to hole"));
+ goto cleanup;
+ } else {
+ /* case 2 */
+ *length = (hole - data);
+ }
+ }
+
+ ret = 0;
+ cleanup:
+ /* At any rate, reposition back to where we started. */
+ if (cur != (off_t) -1)
+ ignore_value(lseek(fd, cur, SEEK_SET));
return ret;
}
diff --git a/src/util/virfile.h b/src/util/virfile.h
index 41c25a2..32a1d3c 100644
--- a/src/util/virfile.h
+++ b/src/util/virfile.h
@@ -340,4 +340,7 @@ int virFileReadValueInt(const char *path, int *value);
int virFileReadValueUint(const char *path, unsigned int *value);
int virFileReadValueBitmap(const char *path, int maxlen, virBitmapPtr *value);
+int virFileInData(int fd,
+ int *inData,
+ unsigned long long *length);
#endif /* __VIR_FILE_H */
diff --git a/tests/virfiletest.c b/tests/virfiletest.c
index 702a76a..3e298dc 100644
--- a/tests/virfiletest.c
+++ b/tests/virfiletest.c
@@ -21,6 +21,7 @@
#include <config.h>
#include <stdlib.h>
+#include <fcntl.h>
#include "testutils.h"
#include "virfile.h"
@@ -119,6 +120,190 @@ testFileSanitizePath(const void *opaque)
static int
+makeSparseFile(const off_t offsets[],
+ const bool startData);
+
+#ifdef __linux__
+/* Create a sparse file. @offsets in KiB. */
+static int
+makeSparseFile(const off_t offsets[],
+ const bool startData)
+{
+ int fd = -1;
+ char path[] = abs_builddir "fileInData.XXXXXX";
+ off_t len = 0;
+ size_t i;
+
+ if ((fd = mkostemp(path, O_CLOEXEC|O_RDWR)) < 0)
+ goto error;
+
+ if (unlink(path) < 0)
+ goto error;
+
+ for (i = 0; offsets[i] != (off_t) -1; i++)
+ len += offsets[i] * 1024;
+
+ while (len) {
+ const char buf[] = "abcdefghijklmnopqrstuvwxyz";
+ off_t toWrite = sizeof(buf);
+
+ if (toWrite > len)
+ toWrite = len;
+
+ if (safewrite(fd, buf, toWrite) < 0) {
+ fprintf(stderr, "unable to write to %s (errno=%d)\n", path, errno);
+ goto error;
+ }
+
+ len -= toWrite;
+ }
+
+ len = 0;
+ for (i = 0; offsets[i] != (off_t) -1; i++) {
+ bool inData = startData;
+
+ if (i % 2)
+ inData = !inData;
+
+ if (!inData &&
+ fallocate(fd,
+ FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
+ len, offsets[i] * 1024) < 0) {
+ fprintf(stderr, "unable to punch a hole at offset %lld length %lld\n",
+ (long long) len, (long long) offsets[i]);
+ goto error;
+ }
+
+ len += offsets[i] * 1024;
+ }
+
+ if (lseek(fd, 0, SEEK_SET) == (off_t) -1) {
+ fprintf(stderr, "unable to lseek (errno=%d)\n", errno);
+ goto error;
+ }
+
+ return fd;
+ error:
+ VIR_FORCE_CLOSE(fd);
+ return -1;
+}
+
+#else /* !__linux__ */
+
+static int
+makeSparseFile(const off_t offsets[] ATTRIBUTE_UNUSED,
+ const bool startData ATTRIBUTE_UNUSED)
+{
+ return -1;
+}
+
+#endif /* !__linux__ */
+
+
+#define EXTENT 4
+static bool
+holesSupported(void)
+{
+ off_t offsets[] = {EXTENT, EXTENT, EXTENT, -1};
+ off_t tmp;
+ int fd;
+ bool ret = false;
+
+ if ((fd = makeSparseFile(offsets, true)) < 0)
+ goto cleanup;
+
+ /* The way this works is: there are 4K of data followed by 4K hole followed
+ * by 4K hole again. Check if the filesystem we are running the test suite
+ * on supports holes. */
+ if ((tmp = lseek(fd, 0, SEEK_DATA)) == (off_t) -1)
+ goto cleanup;
+
+ if (tmp != 0)
+ goto cleanup;
+
+ if ((tmp = lseek(fd, tmp, SEEK_HOLE)) == (off_t) -1)
+ goto cleanup;
+
+ if (tmp != EXTENT * 1024)
+ goto cleanup;
+
+ if ((tmp = lseek(fd, tmp, SEEK_DATA)) == (off_t) -1)
+ goto cleanup;
+
+ if (tmp != 2 * EXTENT * 1024)
+ goto cleanup;
+
+ if ((tmp = lseek(fd, tmp, SEEK_HOLE)) == (off_t) -1)
+ goto cleanup;
+
+ if (tmp != 3 * EXTENT * 1024)
+ goto cleanup;
+
+ ret = true;
+ cleanup:
+ VIR_FORCE_CLOSE(fd);
+ return ret;
+}
+
+
+struct testFileInData {
+ bool startData; /* whether the list of offsets starts with data section */
+ off_t *offsets;
+};
+
+
+static int
+testFileInData(const void *opaque)
+{
+ const struct testFileInData *data = opaque;
+ int fd = -1;
+ int ret = -1;
+ size_t i;
+
+ if ((fd = makeSparseFile(data->offsets, data->startData)) < 0)
+ goto cleanup;
+
+ for (i = 0; data->offsets[i] != (off_t) -1; i++) {
+ bool shouldInData = data->startData;
+ int realInData;
+ unsigned long long shouldLen;
+ unsigned long long realLen;
+
+ if (i % 2)
+ shouldInData = !shouldInData;
+
+ if (virFileInData(fd, &realInData, &realLen) < 0)
+ goto cleanup;
+
+ if (realInData != shouldInData) {
+ fprintf(stderr, "Unexpected data/hole. Expected %s got %s\n",
+ shouldInData ? "data" : "hole",
+ realInData ? "data" : "hole");
+ goto cleanup;
+ }
+
+ shouldLen = data->offsets[i] * 1024;
+ if (realLen != shouldLen) {
+ fprintf(stderr, "Unexpected section length. Expected %lld got %lld\n",
+ shouldLen, realLen);
+ goto cleanup;
+ }
+
+ if (lseek(fd, shouldLen, SEEK_CUR) < 0) {
+ fprintf(stderr, "Unable to seek\n");
+ goto cleanup;
+ }
+ }
+
+ ret = 0;
+
+ cleanup:
+ VIR_FORCE_CLOSE(fd);
+ return ret;
+}
+
+
+static int
mymain(void)
{
int ret = 0;
@@ -186,6 +371,24 @@ mymain(void)
DO_TEST_SANITIZE_PATH_SAME("gluster://bar.baz/fooo//hoo");
DO_TEST_SANITIZE_PATH_SAME("gluster://bar.baz/fooo///////hoo");
+#define DO_TEST_IN_DATA(inData, ...) \
+ do { \
+ off_t offsets[] = {__VA_ARGS__, -1}; \
+ struct testFileInData data = { \
+ .startData = inData, .offsets = offsets, \
+ }; \
+ if (virTestRun(virTestCounterNext(), testFileInData, &data) < 0) \
+ ret = -1; \
+ } while (0)
+
+ if (holesSupported()) {
+ DO_TEST_IN_DATA(true, 4, 4, 4);
+ DO_TEST_IN_DATA(false, 4, 4, 4);
+ DO_TEST_IN_DATA(true, 8, 8, 8);
+ DO_TEST_IN_DATA(false, 8, 8, 8);
+ DO_TEST_IN_DATA(true, 8, 16, 32, 64, 128, 256, 512);
+ DO_TEST_IN_DATA(false, 8, 16, 32, 64, 128, 256, 512);
+ }
return ret != 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}
--
2.10.2
--
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