From b928d140f4c2b44c4ffa0217401cae89a2826906 Mon Sep 17 00:00:00 2001 From: Michal Privoznik Date: Thu, 16 Jun 2016 10:42:47 +0200 Subject: [PATCH] util: Introduce virFileInData 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 --- src/libvirt_private.syms | 1 + src/util/virfile.c | 108 +++++++++++++++++++++ src/util/virfile.h | 4 + tests/virfiletest.c | 203 +++++++++++++++++++++++++++++++++++++++ 4 files changed, 316 insertions(+) diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index bbe283529b..4102a002ba 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -1628,6 +1628,7 @@ virFileGetHugepageSize; virFileGetMountReverseSubtree; virFileGetMountSubtree; virFileHasSuffix; +virFileInData; virFileIsAbsPath; virFileIsDir; virFileIsExecutable; diff --git a/src/util/virfile.c b/src/util/virfile.c index ea44a647ce..2f4bc42b63 100644 --- a/src/util/virfile.c +++ b/src/util/virfile.c @@ -3793,6 +3793,114 @@ virFileComparePaths(const char *p1, const char *p2) cleanup: VIR_FREE(res1); VIR_FREE(res2); + + return ret; +} + + +/** + * virFileInData: + * @fd: file to check + * @inData: true if current position in the @fd is in data section + * @length: amount of bytes until the end of the current section + * + * With sparse files not every extent has to be physically stored on + * the disk. This results in so called data or hole sections. This + * function checks whether the current position in the file @fd is + * in a data section (@inData = 1) or in a hole (@inData = 0). Also, + * it sets @length to match the number of bytes remaining until the + * end of the current section. + * + * As a special case, there is an implicit hole at the end of any + * file. In this case, the function sets @inData = 0, @length = 0. + * + * Upon its return, the position in the @fd is left unchanged, i.e. + * despite this function lseek()-ing back and forth it always + * restores the original position in the file. + * + * NB, @length is type of long long because it corresponds to off_t + * the best. + * + * Returns 0 on success, + * -1 otherwise. + */ +int +virFileInData(int fd, + int *inData, + 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 38e938f87f..57ceb80721 100644 --- a/src/util/virfile.h +++ b/src/util/virfile.h @@ -348,4 +348,8 @@ int virFileReadValueString(char **value, const char *format, ...) ATTRIBUTE_FMT_PRINTF(2, 3); +int virFileInData(int fd, + int *inData, + long long *length); + #endif /* __VIR_FILE_H */ diff --git a/tests/virfiletest.c b/tests/virfiletest.c index 702a76a501..a93bee01ab 100644 --- a/tests/virfiletest.c +++ b/tests/virfiletest.c @@ -21,6 +21,7 @@ #include #include +#include #include "testutils.h" #include "virfile.h" @@ -118,6 +119,190 @@ 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; + long long shouldLen; + 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) { @@ -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; } -- GitLab