On Thu, Feb 13, 2020 at 03:12:24PM -0600, Eric Sandeen wrote: > I had a request from someone who cared about mkfs speed(!) > over a slower network block device to look into using faster > zeroing methods, particularly for the log, during mkfs.xfs. > > e2fsprogs already does this, thanks to some guy named Darrick: > > /* > * If we know about ZERO_RANGE, try that before we try PUNCH_HOLE because > * ZERO_RANGE doesn't unmap preallocated blocks. We prefer fallocate because > * it always invalidates page cache, and libext2fs requires that reads after > * ZERO_RANGE return zeroes. > */ > static int __unix_zeroout(int fd, off_t offset, off_t len) > { > int ret = -1; > > #if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_ZERO_RANGE) > ret = fallocate(fd, FALLOC_FL_ZERO_RANGE, offset, len); > if (ret == 0) > return 0; > #endif > #if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_PUNCH_HOLE) && defined(FALLOC_FL_KEEP_SIZE) > ret = fallocate(fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, > offset, len); > if (ret == 0) > return 0; > #endif > errno = EOPNOTSUPP; > return ret; > } > > and nobody has exploded so far, AFAIK. :) So, floating this idea > for xfsprogs. I'm a little scared of the second #ifdef block above, but > if that's really ok/consistent/safe we could add it too. If FALLOC_FL_PUNCH_HOLE is defined, then FALLOC_FL_KEEP_SIZE is guaranteed to be defined, so that condition check is somewhat redundant. See commit 79124f18b335 ("fs: add hole punching to fallocate").... > The patch moves some defines around too, I could split that up and resend > if this isn't laughed out of the room. > > Thanks, > -Eric > > ===== > > libxfs: use FALLOC_FL_ZERO_RANGE in libxfs_device_zero > > I had a request from someone who cared about mkfs speed(!) > over a slower network block device to look into using faster > zeroing methods, particularly for the log, during mkfs. > > Using FALLOC_FL_ZERO_RANGE is faster in this case than writing > a bunch of zeros across a wire. > > Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx> > --- > > diff --git a/include/linux.h b/include/linux.h > index 8f3c32b0..425badb5 100644 > --- a/include/linux.h > +++ b/include/linux.h > @@ -113,6 +113,26 @@ static __inline__ void platform_uuid_copy(uuid_t *dst, uuid_t *src) > uuid_copy(*dst, *src); > } > > +#ifndef FALLOC_FL_PUNCH_HOLE > +#define FALLOC_FL_PUNCH_HOLE 0x02 > +#endif > + > +#ifndef FALLOC_FL_COLLAPSE_RANGE > +#define FALLOC_FL_COLLAPSE_RANGE 0x08 > +#endif > + > +#ifndef FALLOC_FL_ZERO_RANGE > +#define FALLOC_FL_ZERO_RANGE 0x10 > +#endif > + > +#ifndef FALLOC_FL_INSERT_RANGE > +#define FALLOC_FL_INSERT_RANGE 0x20 > +#endif > + > +#ifndef FALLOC_FL_UNSHARE_RANGE > +#define FALLOC_FL_UNSHARE_RANGE 0x40 > +#endif These were added to allow xfs_io to test these operations before there was userspace support for them. I do not think we should propagate them outside of xfs_io - if they are not supported by the distro at build time, we shouldn't attempt to use them in mkfs. i.e. xfs_io is test-enablement code for developers, mkfs.xfs is production code for users, so different rules kinda exist for them... > diff --git a/libxfs/Makefile b/libxfs/Makefile > index fbcc963a..b4e8864b 100644 > --- a/libxfs/Makefile > +++ b/libxfs/Makefile > @@ -105,6 +105,10 @@ CFILES = cache.c \ > # > #LCFLAGS += > > +ifeq ($(HAVE_FALLOCATE),yes) > +LCFLAGS += -DHAVE_FALLOCATE > +endif HAVE_FALLOCATE comes from an autoconf test. I suspect that this needs to be made more finegrained, testing for fallocate() features, not just just whether the syscall exists. And the above should probably be in include/builddefs.in so that it's available to all of xfsprogs, not just libxfs code... > + > FCFLAGS = -I. > > LTLIBS = $(LIBPTHREAD) $(LIBRT) > diff --git a/libxfs/rdwr.c b/libxfs/rdwr.c > index 0d9d7202..94f63bbf 100644 > --- a/libxfs/rdwr.c > +++ b/libxfs/rdwr.c > @@ -4,6 +4,9 @@ > * All Rights Reserved. > */ > > +#if defined(HAVE_FALLOCATE) > +#include <linux/falloc.h> > +#endif Urk. That should be in include/linux.h, right? > > #include "libxfs_priv.h" > #include "init.h" > @@ -60,9 +63,21 @@ int > libxfs_device_zero(struct xfs_buftarg *btp, xfs_daddr_t start, uint len) > { > xfs_off_t start_offset, end_offset, offset; > - ssize_t zsize, bytes; > + ssize_t zsize, bytes, len_bytes; > char *z; > - int fd; > + int ret, fd; > + > + fd = libxfs_device_to_fd(btp->dev); > + start_offset = LIBXFS_BBTOOFF64(start); > + end_offset = LIBXFS_BBTOOFF64(start + len) - start_offset; > + > +#if defined(HAVE_FALLOCATE) > + /* try to use special zeroing methods, fall back to writes if needed */ > + len_bytes = LIBXFS_BBTOOFF64(len); > + ret = fallocate(fd, FALLOC_FL_ZERO_RANGE, start_offset, len_bytes); > + if (ret == 0) > + return 0; > +#endif I kinda dislike the "return if success" hidden inside the ifdef - it's not a code pattern I'd expect to see. This is what I'd tend to expect in include/linux.h: #if defined(HAVE_FALLOCATE_ZERO_RANGE) static inline int platform_zero_range( int fd, xfs_off_t start_offset, xfs_off_t end_offset) { int ret; ret = fallocate(fd, FALLOC_FL_ZERO_RANGE, start_offset, len_bytes); if (!ret) return 0; return -errno; } #else #define platform_zero_range(fd, s, o) (true) #endif and then the code in libxfs_device_zero() does: error = platform_zero_range(fd, start_offset, len_bytes); if (!error) return 0; without adding nasty #defines... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx