On Sun, Aug 19, 2018 at 01:13:05AM +0300, Nir Soffer wrote: Can you put stdbook after stdlib for consistency with the other source files. Spacing. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html

File systems not supporting FALLOC_FL_ZERO_RANGE yet fall back to manual zeroing. We can avoid this by combining two fallocate calls: fallocate(FALLOC_FL_PUNCH_HOLE) fallocate(0) Based on my tests this is much more efficient compared to manual zeroing. The idea came from this qemu patch: https://github.com/qemu/qemu/commit/1cdc3239f1bb Here is an example run with NFS 4.2 without this change, converting fedora 27 image created with virt-builder: $ export SOCK=/tmp/nbd.sock $ export FILE=/nfs-mount/fedora-27.img $ src/nbdkit plugins/file/.libs/nbdkit-file-plugin.so file=$FILE -U $SOCK $ time qemu-img convert -n -f raw -O raw /var/tmp/fedora-27.img nbd:unix:/tmp/nbd.sock real 0m17.481s user 0m0.199s sys 0m0.691s $ time qemu-img convert -n -f raw -O raw -W /var/tmp/fedora-27.img nbd:unix:/tmp/nbd.sock real 0m17.072s user 0m0.191s sys 0m0.738s With this change: $ time qemu-img convert -n -f raw -O raw /var/tmp/fedora-27.img nbd:unix:/tmp/nbd.sock real 0m6.285s user 0m0.217s sys 0m0.829s $ time qemu-img convert -n -f raw -O raw -W /var/tmp/fedora-27.img nbd:unix:/tmp/nbd.sock real 0m3.967s user 0m0.193s sys 0m0.702s Note: the image is sparse, but nbdkit creates a fully allocated image. This may be a bug in nbdkit or qemu-img. --- plugins/file/file.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/plugins/file/file.c b/plugins/file/file.c index 5daab63..e96aa86 100644 --- a/plugins/file/file.c +++ b/plugins/file/file.c @@ -121,6 +121,7 @@ struct handle { int fd; bool can_punch_hole; bool can_zero_range; + bool can_fallocate; }; /* Create the per-connection handle. */ @@ -161,6 +162,8 @@ file_open (int readonly) h->can_zero_range = false; #endif + h->can_fallocate = true; + return h; } @@ -301,6 +304,35 @@ file_zero (void *handle, uint32_t count, uint64_t offset, int may_trim) } #endif +#ifdef FALLOC_FL_PUNCH_HOLE + /* If we can punch hole but may not trim, we can combine punching hole and + * fallocate to zero a range. This is expected to be more efficient than + * writing zeros manually. */ + if (h->can_punch_hole && h->can_fallocate) { + r = do_fallocate (h->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, + offset, count); + if (r == 0) { + r = do_fallocate (h->fd, 0, offset, count); + if (r == 0) + return r; + + if (errno != EOPNOTSUPP) { + nbdkit_error ("zero: %m"); + return r; + } + + h->can_fallocate = false; + } else { + if (errno != EOPNOTSUPP) { + nbdkit_error ("zero: %m"); + return r; + } + + h->can_punch_hole = false; + } + } +#endif + /* Trigger a fall back to writing */ errno = EOPNOTSUPP; return r; -- 2.17.1

On Sun, Aug 19, 2018 at 01:13:07AM +0300, Nir Soffer wrote: You have to add this file to common/include/Makefile.am otherwise it will never be distributed. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org

fallocate(FALLOC_FL_ZERO_RANGE) is supported for block devices with modern kernel, but when it is not, we fall back to manual zeroing. For block device, try also to use ioctl(BLKZEROOUT) if offset and count are aligned to block device sector size. Here is an example run without this change on RHEL 7.5: $ export SOCK=/tmp/nbd.sock $ export BLOCK=/dev/e30bfac2-8e13-479d-8cd6-c6da5e306c4e/c9864222-bc52-4359-80d7-76e47d619b15 $ src/nbdkit plugins/file/.libs/nbdkit-file-plugin.so file=$BLOCK -U $SOCK $ time qemu-img convert -n -f raw -O raw /var/tmp/fedora-27.img nbd:unix:/tmp/nbd.sock real 0m11.563s user 0m0.219s sys 0m0.746s $ time qemu-img convert -n -f raw -O raw -W /var/tmp/fedora-27.img nbd:unix:/tmp/nbd.sock real 0m9.841s user 0m0.167s sys 0m0.715s With this change: $ time qemu-img convert -n -f raw -O raw /var/tmp/fedora-27.img nbd:unix:/tmp/nbd.sock real 0m2.796s user 0m0.202s sys 0m0.700s $ time qemu-img convert -n -f raw -O raw -W /var/tmp/fedora-27.img nbd:unix:/tmp/nbd.sock real 0m1.908s user 0m0.166s sys 0m0.728s --- plugins/file/Makefile.am | 3 +- plugins/file/file.c | 70 +++++++++++++++++++++++++++++++++------- 2 files changed, 61 insertions(+), 12 deletions(-) diff --git a/plugins/file/Makefile.am b/plugins/file/Makefile.am index 00eaf59..91adbcb 100644 --- a/plugins/file/Makefile.am +++ b/plugins/file/Makefile.am @@ -41,7 +41,8 @@ nbdkit_file_plugin_la_SOURCES = \ $(top_srcdir)/include/nbdkit-plugin.h nbdkit_file_plugin_la_CPPFLAGS = \ - -I$(top_srcdir)/include + -I$(top_srcdir)/include \ + -I$(top_srcdir)/common/include nbdkit_file_plugin_la_CFLAGS = \ $(WARNINGS_CFLAGS) nbdkit_file_plugin_la_LDFLAGS = \ diff --git a/plugins/file/file.c b/plugins/file/file.c index e96aa86..a0c7b0b 100644 --- a/plugins/file/file.c +++ b/plugins/file/file.c @@ -41,14 +41,21 @@ #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> +#include <sys/ioctl.h> #include <errno.h> #if defined(__linux__) && !defined(FALLOC_FL_PUNCH_HOLE) #include <linux/falloc.h> /* For FALLOC_FL_*, glibc < 2.18 */ #endif +#if defined(__linux__) +#include <linux/fs.h> /* For BLKZEROOUT */ +#endif + #include <nbdkit-plugin.h> +#include "isaligned.h" + #ifndef O_CLOEXEC #define O_CLOEXEC 0 #endif @@ -119,9 +126,12 @@ file_config_complete (void) /* The per-connection handle. */ struct handle { int fd; + bool is_block_device; + int sector_size; bool can_punch_hole; bool can_zero_range; bool can_fallocate; + bool can_zeroout; }; /* Create the per-connection handle. */ @@ -129,6 +139,7 @@ static void * file_open (int readonly) { struct handle *h; + struct stat statbuf; int flags; h = malloc (sizeof *h); @@ -150,6 +161,22 @@ file_open (int readonly) return NULL; } + if (fstat (h->fd, &statbuf) == -1) { + nbdkit_error ("fstat: %s: %m", filename); + free (h); + return NULL; + } + + h->is_block_device = S_ISBLK(statbuf.st_mode); + h->sector_size = 4096; /* Start with safe guess */ + +#ifdef BLKSSZGET + if (h->is_block_device) { + if (ioctl (h->fd, BLKSSZGET, &h->sector_size)) + nbdkit_debug ("cannot get sector size: %s: %m", filename); + } +#endif + #ifdef FALLOC_FL_PUNCH_HOLE h->can_punch_hole = true; #else @@ -163,6 +190,7 @@ file_open (int readonly) #endif h->can_fallocate = true; + h->can_zeroout = h->is_block_device; return h; } @@ -184,27 +212,29 @@ static int64_t file_get_size (void *handle) { struct handle *h = handle; - struct stat statbuf; - if (fstat (h->fd, &statbuf) == -1) { - nbdkit_error ("stat: %m"); - return -1; - } - - if (S_ISBLK (statbuf.st_mode)) { + if (h->is_block_device) { + /* Block device, so st_size will not be the true size. */ off_t size; - /* Block device, so st_size will not be the true size. */ size = lseek (h->fd, 0, SEEK_END); if (size == -1) { nbdkit_error ("lseek (to find device size): %m"); return -1; } + return size; - } + } else { + /* Regular file. */ + struct stat statbuf; - /* Else regular file. */ - return statbuf.st_size; + if (fstat (h->fd, &statbuf) == -1) { + nbdkit_error ("fstat: %m"); + return -1; + } + + return statbuf.st_size; + } } static int @@ -333,6 +363,24 @@ file_zero (void *handle, uint32_t count, uint64_t offset, int may_trim) } #endif +#ifdef BLKZEROOUT + /* For aligned range and block device, we can use BLKZEROOUT. */ + if (h->can_zeroout && is_aligned (offset | count, h->sector_size)) { + uint64_t range[2] = {offset, count}; + + r = ioctl (h->fd, BLKZEROOUT, &range); + if (r == 0) + return r; + + if (errno != ENOTTY) { + nbdkit_error ("zero: %m"); + return r; + } + + h->can_zeroout = false; + } +#endif + /* Trigger a fall back to writing */ errno = EOPNOTSUPP; return r; -- 2.17.1