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[Qemu-devel] [PULL 76/85] block/file-posix: Generalize raw_regular_trunc
From: |
Max Reitz |
Subject: |
[Qemu-devel] [PULL 76/85] block/file-posix: Generalize raw_regular_truncate |
Date: |
Tue, 11 Jul 2017 18:08:05 +0200 |
Currently, raw_regular_truncate() is intended for setting the size of a
newly created file. However, we also want to use it for truncating an
existing file in which case only the newly added space (when growing)
should be preallocated.
This also means that if resizing failed, we should try to restore the
original file size. This is important when using preallocation.
Signed-off-by: Max Reitz <address@hidden>
Reviewed-by: Philippe Mathieu-Daudé <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
Message-id: address@hidden
Signed-off-by: Max Reitz <address@hidden>
---
block/file-posix.c | 61 ++++++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 50 insertions(+), 11 deletions(-)
diff --git a/block/file-posix.c b/block/file-posix.c
index deefd6e..59154ea 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1624,11 +1624,31 @@ static void raw_close(BlockDriverState *bs)
}
}
+/**
+ * Truncates the given regular file @fd to @offset and, when growing, fills the
+ * new space according to @prealloc.
+ *
+ * Returns: 0 on success, -errno on failure.
+ */
static int raw_regular_truncate(int fd, int64_t offset, PreallocMode prealloc,
Error **errp)
{
int result = 0;
- char *buf;
+ int64_t current_length = 0;
+ char *buf = NULL;
+ struct stat st;
+
+ if (fstat(fd, &st) < 0) {
+ result = -errno;
+ error_setg_errno(errp, -result, "Could not stat file");
+ return result;
+ }
+
+ current_length = st.st_size;
+ if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
+ error_setg(errp, "Cannot use preallocation for shrinking files");
+ return -ENOTSUP;
+ }
switch (prealloc) {
#ifdef CONFIG_POSIX_FALLOCATE
@@ -1638,17 +1658,17 @@ static int raw_regular_truncate(int fd, int64_t offset,
PreallocMode prealloc,
* file systems that do not support fallocate(), trying to check if a
* block is allocated before allocating it, so don't do that here.
*/
- result = -posix_fallocate(fd, 0, offset);
+ result = -posix_fallocate(fd, current_length, offset - current_length);
if (result != 0) {
/* posix_fallocate() doesn't set errno. */
error_setg_errno(errp, -result,
- "Could not preallocate data for the new file");
+ "Could not preallocate new data");
}
- return result;
+ goto out;
#endif
case PREALLOC_MODE_FULL:
{
- int64_t num = 0, left = offset;
+ int64_t num = 0, left = offset - current_length;
/*
* Knowing the final size from the beginning could allow the file
@@ -1658,19 +1678,27 @@ static int raw_regular_truncate(int fd, int64_t offset,
PreallocMode prealloc,
if (ftruncate(fd, offset) != 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not resize file");
- return result;
+ goto out;
}
buf = g_malloc0(65536);
+ result = lseek(fd, current_length, SEEK_SET);
+ if (result < 0) {
+ result = -errno;
+ error_setg_errno(errp, -result,
+ "Failed to seek to the old end of file");
+ goto out;
+ }
+
while (left > 0) {
num = MIN(left, 65536);
result = write(fd, buf, num);
if (result < 0) {
result = -errno;
error_setg_errno(errp, -result,
- "Could not write to the new file");
- break;
+ "Could not write zeros for preallocation");
+ goto out;
}
left -= result;
}
@@ -1679,11 +1707,11 @@ static int raw_regular_truncate(int fd, int64_t offset,
PreallocMode prealloc,
if (result < 0) {
result = -errno;
error_setg_errno(errp, -result,
- "Could not flush new file to disk");
+ "Could not flush file to disk");
+ goto out;
}
}
- g_free(buf);
- return result;
+ goto out;
}
case PREALLOC_MODE_OFF:
if (ftruncate(fd, offset) != 0) {
@@ -1697,6 +1725,17 @@ static int raw_regular_truncate(int fd, int64_t offset,
PreallocMode prealloc,
PreallocMode_lookup[prealloc]);
return result;
}
+
+out:
+ if (result < 0) {
+ if (ftruncate(fd, current_length) < 0) {
+ error_report("Failed to restore old file length: %s",
+ strerror(errno));
+ }
+ }
+
+ g_free(buf);
+ return result;
}
static int raw_truncate(BlockDriverState *bs, int64_t offset,
--
2.9.4
- [Qemu-devel] [PULL 57/85] iotests: chown LUKS device before qemu-io launches, (continued)
- [Qemu-devel] [PULL 57/85] iotests: chown LUKS device before qemu-io launches, Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 70/85] block: Add PreallocMode to BD.bdrv_truncate(), Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 71/85] block: Add PreallocMode to bdrv_truncate(), Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 69/85] iotests: add test 178 for qemu-img measure, Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 74/85] block/file-posix: Small fixes in raw_create(), Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 72/85] block: Add PreallocMode to blk_truncate(), Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 75/85] block/file-posix: Extract raw_regular_truncate(), Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 73/85] qemu-img: Expose PreallocMode for resizing, Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 78/85] block/qcow2: Generalize preallocate(), Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 77/85] block/file-posix: Preallocation for truncate, Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 76/85] block/file-posix: Generalize raw_regular_truncate,
Max Reitz <=
- [Qemu-devel] [PULL 79/85] block/qcow2: Lock s->lock in preallocate(), Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 80/85] block/qcow2: Metadata preallocation for truncate, Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 81/85] block/qcow2: Add qcow2_refcount_area(), Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 82/85] block/qcow2: Rename "fail_block" to just "fail", Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 83/85] block/qcow2: falloc/full preallocating growth, Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 84/85] iotests: Add preallocated resize test for raw, Max Reitz, 2017/07/11
- [Qemu-devel] [PULL 85/85] iotests: Add preallocated growth test for qcow2, Max Reitz, 2017/07/11
- Re: [Qemu-devel] [PULL 00/85] Block layer patches, Peter Maydell, 2017/07/13