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-rw-r--r--block/qed.c6
-rw-r--r--block/raw-posix.c25
-rw-r--r--block/vdi.c29
-rw-r--r--block/vmdk.c6
-rw-r--r--block/vpc.c29
-rw-r--r--include/block/block_int.h1
-rw-r--r--qemu-doc.texi16
-rw-r--r--qemu-img.texi16
-rw-r--r--tests/qemu-iotests/082.out24
9 files changed, 146 insertions, 6 deletions
diff --git a/block/qed.c b/block/qed.c
index eddae92..b69374b 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -567,7 +567,7 @@ static void bdrv_qed_close(BlockDriverState *bs)
static int qed_create(const char *filename, uint32_t cluster_size,
uint64_t image_size, uint32_t table_size,
const char *backing_file, const char *backing_fmt,
- Error **errp)
+ QemuOpts *opts, Error **errp)
{
QEDHeader header = {
.magic = QED_MAGIC,
@@ -586,7 +586,7 @@ static int qed_create(const char *filename, uint32_t cluster_size,
int ret = 0;
BlockDriverState *bs;
- ret = bdrv_create_file(filename, NULL, &local_err);
+ ret = bdrv_create_file(filename, opts, &local_err);
if (ret < 0) {
error_propagate(errp, local_err);
return ret;
@@ -682,7 +682,7 @@ static int bdrv_qed_create(const char *filename, QemuOpts *opts, Error **errp)
}
ret = qed_create(filename, cluster_size, image_size, table_size,
- backing_file, backing_fmt, errp);
+ backing_file, backing_fmt, opts, errp);
finish:
g_free(backing_file);
diff --git a/block/raw-posix.c b/block/raw-posix.c
index dacf4fb..825a0c8 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -55,6 +55,9 @@
#include <linux/cdrom.h>
#include <linux/fd.h>
#include <linux/fs.h>
+#ifndef FS_NOCOW_FL
+#define FS_NOCOW_FL 0x00800000 /* Do not cow file */
+#endif
#endif
#ifdef CONFIG_FIEMAP
#include <linux/fiemap.h>
@@ -1278,12 +1281,14 @@ static int raw_create(const char *filename, QemuOpts *opts, Error **errp)
int fd;
int result = 0;
int64_t total_size = 0;
+ bool nocow = false;
strstart(filename, "file:", &filename);
/* Read out options */
total_size =
qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0) / BDRV_SECTOR_SIZE;
+ nocow = qemu_opt_get_bool(opts, BLOCK_OPT_NOCOW, false);
fd = qemu_open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
0644);
@@ -1291,6 +1296,21 @@ static int raw_create(const char *filename, QemuOpts *opts, Error **errp)
result = -errno;
error_setg_errno(errp, -result, "Could not create file");
} else {
+ if (nocow) {
+#ifdef __linux__
+ /* Set NOCOW flag to solve performance issue on fs like btrfs.
+ * This is an optimisation. The FS_IOC_SETFLAGS ioctl return value
+ * will be ignored since any failure of this operation should not
+ * block the left work.
+ */
+ int attr;
+ if (ioctl(fd, FS_IOC_GETFLAGS, &attr) == 0) {
+ attr |= FS_NOCOW_FL;
+ ioctl(fd, FS_IOC_SETFLAGS, &attr);
+ }
+#endif
+ }
+
if (ftruncate(fd, total_size * BDRV_SECTOR_SIZE) != 0) {
result = -errno;
error_setg_errno(errp, -result, "Could not resize file");
@@ -1477,6 +1497,11 @@ static QemuOptsList raw_create_opts = {
.type = QEMU_OPT_SIZE,
.help = "Virtual disk size"
},
+ {
+ .name = BLOCK_OPT_NOCOW,
+ .type = QEMU_OPT_BOOL,
+ .help = "Turn off copy-on-write (valid only on btrfs)"
+ },
{ /* end of list */ }
}
};
diff --git a/block/vdi.c b/block/vdi.c
index 01fe22e..197bd77 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -53,6 +53,13 @@
#include "block/block_int.h"
#include "qemu/module.h"
#include "migration/migration.h"
+#ifdef __linux__
+#include <linux/fs.h>
+#include <sys/ioctl.h>
+#ifndef FS_NOCOW_FL
+#define FS_NOCOW_FL 0x00800000 /* Do not cow file */
+#endif
+#endif
#if defined(CONFIG_UUID)
#include <uuid/uuid.h>
@@ -683,6 +690,7 @@ static int vdi_create(const char *filename, QemuOpts *opts, Error **errp)
VdiHeader header;
size_t i;
size_t bmap_size;
+ bool nocow = false;
logout("\n");
@@ -699,6 +707,7 @@ static int vdi_create(const char *filename, QemuOpts *opts, Error **errp)
image_type = VDI_TYPE_STATIC;
}
#endif
+ nocow = qemu_opt_get_bool_del(opts, BLOCK_OPT_NOCOW, false);
if (bytes > VDI_DISK_SIZE_MAX) {
result = -ENOTSUP;
@@ -716,6 +725,21 @@ static int vdi_create(const char *filename, QemuOpts *opts, Error **errp)
goto exit;
}
+ if (nocow) {
+#ifdef __linux__
+ /* Set NOCOW flag to solve performance issue on fs like btrfs.
+ * This is an optimisation. The FS_IOC_SETFLAGS ioctl return value will
+ * be ignored since any failure of this operation should not block the
+ * left work.
+ */
+ int attr;
+ if (ioctl(fd, FS_IOC_GETFLAGS, &attr) == 0) {
+ attr |= FS_NOCOW_FL;
+ ioctl(fd, FS_IOC_SETFLAGS, &attr);
+ }
+#endif
+ }
+
/* We need enough blocks to store the given disk size,
so always round up. */
blocks = (bytes + block_size - 1) / block_size;
@@ -818,6 +842,11 @@ static QemuOptsList vdi_create_opts = {
.def_value_str = "off"
},
#endif
+ {
+ .name = BLOCK_OPT_NOCOW,
+ .type = QEMU_OPT_BOOL,
+ .help = "Turn off copy-on-write (valid only on btrfs)"
+ },
/* TODO: An additional option to set UUID values might be useful. */
{ /* end of list */ }
}
diff --git a/block/vmdk.c b/block/vmdk.c
index d0de019..27a78da 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1529,7 +1529,7 @@ static int coroutine_fn vmdk_co_write_zeroes(BlockDriverState *bs,
static int vmdk_create_extent(const char *filename, int64_t filesize,
bool flat, bool compress, bool zeroed_grain,
- Error **errp)
+ QemuOpts *opts, Error **errp)
{
int ret, i;
BlockDriverState *bs = NULL;
@@ -1539,7 +1539,7 @@ static int vmdk_create_extent(const char *filename, int64_t filesize,
uint32_t *gd_buf = NULL;
int gd_buf_size;
- ret = bdrv_create_file(filename, NULL, &local_err);
+ ret = bdrv_create_file(filename, opts, &local_err);
if (ret < 0) {
error_propagate(errp, local_err);
goto exit;
@@ -1845,7 +1845,7 @@ static int vmdk_create(const char *filename, QemuOpts *opts, Error **errp)
path, desc_filename);
if (vmdk_create_extent(ext_filename, size,
- flat, compress, zeroed_grain, errp)) {
+ flat, compress, zeroed_grain, opts, errp)) {
ret = -EINVAL;
goto exit;
}
diff --git a/block/vpc.c b/block/vpc.c
index 798d854..8b376a4 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -29,6 +29,13 @@
#if defined(CONFIG_UUID)
#include <uuid/uuid.h>
#endif
+#ifdef __linux__
+#include <linux/fs.h>
+#include <sys/ioctl.h>
+#ifndef FS_NOCOW_FL
+#define FS_NOCOW_FL 0x00800000 /* Do not cow file */
+#endif
+#endif
/**************************************************************/
@@ -751,6 +758,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
int64_t total_size;
int disk_type;
int ret = -EIO;
+ bool nocow = false;
/* Read out options */
total_size = qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0);
@@ -767,6 +775,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
} else {
disk_type = VHD_DYNAMIC;
}
+ nocow = qemu_opt_get_bool_del(opts, BLOCK_OPT_NOCOW, false);
/* Create the file */
fd = qemu_open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0644);
@@ -775,6 +784,21 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
goto out;
}
+ if (nocow) {
+#ifdef __linux__
+ /* Set NOCOW flag to solve performance issue on fs like btrfs.
+ * This is an optimisation. The FS_IOC_SETFLAGS ioctl return value will
+ * be ignored since any failure of this operation should not block the
+ * left work.
+ */
+ int attr;
+ if (ioctl(fd, FS_IOC_GETFLAGS, &attr) == 0) {
+ attr |= FS_NOCOW_FL;
+ ioctl(fd, FS_IOC_SETFLAGS, &attr);
+ }
+#endif
+ }
+
/*
* Calculate matching total_size and geometry. Increase the number of
* sectors requested until we get enough (or fail). This ensures that
@@ -884,6 +908,11 @@ static QemuOptsList vpc_create_opts = {
"Type of virtual hard disk format. Supported formats are "
"{dynamic (default) | fixed} "
},
+ {
+ .name = BLOCK_OPT_NOCOW,
+ .type = QEMU_OPT_BOOL,
+ .help = "Turn off copy-on-write (valid only on btrfs)"
+ },
{ /* end of list */ }
}
};
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 53e77cf..eaf6e31 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -54,6 +54,7 @@
#define BLOCK_OPT_LAZY_REFCOUNTS "lazy_refcounts"
#define BLOCK_OPT_ADAPTER_TYPE "adapter_type"
#define BLOCK_OPT_REDUNDANCY "redundancy"
+#define BLOCK_OPT_NOCOW "nocow"
typedef struct BdrvTrackedRequest {
BlockDriverState *bs;
diff --git a/qemu-doc.texi b/qemu-doc.texi
index 88ec9bb..ad92c85 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -589,6 +589,22 @@ check -r all} is required, which may take some time.
This option can only be enabled if @code{compat=1.1} is specified.
+@item nocow
+If this option is set to @code{on}, it will trun off COW of the file. It's only
+valid on btrfs, no effect on other file systems.
+
+Btrfs has low performance when hosting a VM image file, even more when the guest
+on the VM also using btrfs as file system. Turning off COW is a way to mitigate
+this bad performance. Generally there are two ways to turn off COW on btrfs:
+a) Disable it by mounting with nodatacow, then all newly created files will be
+NOCOW. b) For an empty file, add the NOCOW file attribute. That's what this option
+does.
+
+Note: this option is only valid to new or empty files. If there is an existing
+file which is COW and has data blocks already, it couldn't be changed to NOCOW
+by setting @code{nocow=on}. One can issue @code{lsattr filename} to check if
+the NOCOW flag is set or not (Capitabl 'C' is NOCOW flag).
+
@end table
@item qed
diff --git a/qemu-img.texi b/qemu-img.texi
index c68b541..8496f3b 100644
--- a/qemu-img.texi
+++ b/qemu-img.texi
@@ -474,6 +474,22 @@ check -r all} is required, which may take some time.
This option can only be enabled if @code{compat=1.1} is specified.
+@item nocow
+If this option is set to @code{on}, it will trun off COW of the file. It's only
+valid on btrfs, no effect on other file systems.
+
+Btrfs has low performance when hosting a VM image file, even more when the guest
+on the VM also using btrfs as file system. Turning off COW is a way to mitigate
+this bad performance. Generally there are two ways to turn off COW on btrfs:
+a) Disable it by mounting with nodatacow, then all newly created files will be
+NOCOW. b) For an empty file, add the NOCOW file attribute. That's what this option
+does.
+
+Note: this option is only valid to new or empty files. If there is an existing
+file which is COW and has data blocks already, it couldn't be changed to NOCOW
+by setting @code{nocow=on}. One can issue @code{lsattr filename} to check if
+the NOCOW flag is set or not (Capitabl 'C' is NOCOW flag).
+
@end table
@item Other
diff --git a/tests/qemu-iotests/082.out b/tests/qemu-iotests/082.out
index 28309a0..413e7ef 100644
--- a/tests/qemu-iotests/082.out
+++ b/tests/qemu-iotests/082.out
@@ -66,6 +66,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: create -f qcow2 -o ? TEST_DIR/t.qcow2 128M
Supported options:
@@ -77,6 +78,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: create -f qcow2 -o cluster_size=4k,help TEST_DIR/t.qcow2 128M
Supported options:
@@ -88,6 +90,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: create -f qcow2 -o cluster_size=4k,? TEST_DIR/t.qcow2 128M
Supported options:
@@ -99,6 +102,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: create -f qcow2 -o help,cluster_size=4k TEST_DIR/t.qcow2 128M
Supported options:
@@ -110,6 +114,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: create -f qcow2 -o ?,cluster_size=4k TEST_DIR/t.qcow2 128M
Supported options:
@@ -121,6 +126,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: create -f qcow2 -o cluster_size=4k -o help TEST_DIR/t.qcow2 128M
Supported options:
@@ -132,6 +138,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: create -f qcow2 -o cluster_size=4k -o ? TEST_DIR/t.qcow2 128M
Supported options:
@@ -143,6 +150,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: create -f qcow2 -o backing_file=TEST_DIR/t.qcow2,,help TEST_DIR/t.qcow2 128M
Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=134217728 backing_file='TEST_DIR/t.qcow2,help' encryption=off cluster_size=65536 lazy_refcounts=off
@@ -247,6 +255,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: convert -O qcow2 -o ? TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
Supported options:
@@ -258,6 +267,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: convert -O qcow2 -o cluster_size=4k,help TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
Supported options:
@@ -269,6 +279,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: convert -O qcow2 -o cluster_size=4k,? TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
Supported options:
@@ -280,6 +291,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: convert -O qcow2 -o help,cluster_size=4k TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
Supported options:
@@ -291,6 +303,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: convert -O qcow2 -o ?,cluster_size=4k TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
Supported options:
@@ -302,6 +315,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: convert -O qcow2 -o cluster_size=4k -o help TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
Supported options:
@@ -313,6 +327,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: convert -O qcow2 -o cluster_size=4k -o ? TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
Supported options:
@@ -324,6 +339,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: convert -O qcow2 -o backing_file=TEST_DIR/t.qcow2,,help TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
qemu-img: Could not open 'TEST_DIR/t.qcow2.base': Could not open backing file: Could not open 'TEST_DIR/t.qcow2,help': No such file or directory
@@ -417,6 +433,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: amend -f qcow2 -o ? TEST_DIR/t.qcow2
Supported options:
@@ -428,6 +445,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: amend -f qcow2 -o cluster_size=4k,help TEST_DIR/t.qcow2
Supported options:
@@ -439,6 +457,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: amend -f qcow2 -o cluster_size=4k,? TEST_DIR/t.qcow2
Supported options:
@@ -450,6 +469,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: amend -f qcow2 -o help,cluster_size=4k TEST_DIR/t.qcow2
Supported options:
@@ -461,6 +481,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: amend -f qcow2 -o ?,cluster_size=4k TEST_DIR/t.qcow2
Supported options:
@@ -472,6 +493,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: amend -f qcow2 -o cluster_size=4k -o help TEST_DIR/t.qcow2
Supported options:
@@ -483,6 +505,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: amend -f qcow2 -o cluster_size=4k -o ? TEST_DIR/t.qcow2
Supported options:
@@ -494,6 +517,7 @@ encryption Encrypt the image
cluster_size qcow2 cluster size
preallocation Preallocation mode (allowed values: off, metadata)
lazy_refcounts Postpone refcount updates
+nocow Turn off copy-on-write (valid only on btrfs)
Testing: amend -f qcow2 -o backing_file=TEST_DIR/t.qcow2,,help TEST_DIR/t.qcow2
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