diff mbox

[v2,02/27] Add libbtrfsutil

Message ID 5882a6f0414a436bd7a4cfaae938e451724684ac.1518720598.git.osandov@fb.com (mailing list archive)
State New, archived
Headers show

Commit Message

Omar Sandoval Feb. 15, 2018, 7:04 p.m. UTC
From: Omar Sandoval <osandov@fb.com>

Currently, users wishing to manage Btrfs filesystems programatically
have to shell out to btrfs-progs and parse the output. This isn't ideal.
The goal of libbtrfsutil is to provide a library version of as many of
the operations of btrfs-progs as possible and to migrate btrfs-progs to
use it.

Rather than simply refactoring the existing btrfs-progs code, the code
has to be written from scratch for a couple of reasons:

* A lot of the btrfs-progs code was not designed with a nice library API
  in mind in terms of reusability, naming, and error reporting.
* libbtrfsutil is licensed under the LGPL, whereas btrfs-progs is under
  the GPL, which makes it dubious to directly copy or move the code.

Eventually, most of the low-level btrfs-progs code should either live in
libbtrfsutil or the shared kernel/userspace filesystem code, and
btrfs-progs will just be the CLI wrapper.

This first commit just includes the build system changes, license,
README, and error reporting helper.

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 .gitignore                        |   2 +
 Makefile                          |  72 ++--
 Makefile.inc.in                   |   2 +-
 libbtrfsutil/COPYING              | 674 ++++++++++++++++++++++++++++++++++++++
 libbtrfsutil/COPYING.LESSER       | 165 ++++++++++
 libbtrfsutil/README.md            |  35 ++
 libbtrfsutil/btrfsutil.h          |  76 +++++
 libbtrfsutil/btrfsutil_internal.h |  40 +++
 libbtrfsutil/errors.c             |  55 ++++
 9 files changed, 1100 insertions(+), 21 deletions(-)
 create mode 100644 libbtrfsutil/COPYING
 create mode 100644 libbtrfsutil/COPYING.LESSER
 create mode 100644 libbtrfsutil/README.md
 create mode 100644 libbtrfsutil/btrfsutil.h
 create mode 100644 libbtrfsutil/btrfsutil_internal.h
 create mode 100644 libbtrfsutil/errors.c

Comments

Liu Bo Feb. 20, 2018, 5:32 p.m. UTC | #1
On Thu, Feb 15, 2018 at 11:04:47AM -0800, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> Currently, users wishing to manage Btrfs filesystems programatically
> have to shell out to btrfs-progs and parse the output. This isn't ideal.
> The goal of libbtrfsutil is to provide a library version of as many of
> the operations of btrfs-progs as possible and to migrate btrfs-progs to
> use it.
> 
> Rather than simply refactoring the existing btrfs-progs code, the code
> has to be written from scratch for a couple of reasons:
> 
> * A lot of the btrfs-progs code was not designed with a nice library API
>   in mind in terms of reusability, naming, and error reporting.
> * libbtrfsutil is licensed under the LGPL, whereas btrfs-progs is under
>   the GPL, which makes it dubious to directly copy or move the code.
> 
> Eventually, most of the low-level btrfs-progs code should either live in
> libbtrfsutil or the shared kernel/userspace filesystem code, and
> btrfs-progs will just be the CLI wrapper.
> 
> This first commit just includes the build system changes, license,
> README, and error reporting helper.
> 
> Signed-off-by: Omar Sandoval <osandov@fb.com>
> ---
>  .gitignore                        |   2 +
>  Makefile                          |  72 ++--
>  Makefile.inc.in                   |   2 +-
>  libbtrfsutil/COPYING              | 674 ++++++++++++++++++++++++++++++++++++++
>  libbtrfsutil/COPYING.LESSER       | 165 ++++++++++
>  libbtrfsutil/README.md            |  35 ++
>  libbtrfsutil/btrfsutil.h          |  76 +++++
>  libbtrfsutil/btrfsutil_internal.h |  40 +++
>  libbtrfsutil/errors.c             |  55 ++++
>  9 files changed, 1100 insertions(+), 21 deletions(-)
>  create mode 100644 libbtrfsutil/COPYING
>  create mode 100644 libbtrfsutil/COPYING.LESSER
>  create mode 100644 libbtrfsutil/README.md
>  create mode 100644 libbtrfsutil/btrfsutil.h
>  create mode 100644 libbtrfsutil/btrfsutil_internal.h
>  create mode 100644 libbtrfsutil/errors.c
> 
> diff --git a/.gitignore b/.gitignore
> index 8e607f6e..272d53e4 100644
> --- a/.gitignore
> +++ b/.gitignore
> @@ -43,6 +43,8 @@ libbtrfs.so.0.1
>  library-test
>  library-test-static
>  /fssum
> +/libbtrfsutil.so*
> +/libbtrfsutil.a
>

.gitignore is not part of btrfs-progs, is it?

I Skipped Makefile, the .c and .h look good to me, 

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>

Thanks,

-liubo

>  /tests/*-tests-results.txt
>  /tests/test-console.txt
> diff --git a/Makefile b/Makefile
> index 00e21379..7fb70d06 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -73,10 +73,20 @@ CFLAGS = $(SUBST_CFLAGS) \
>  	 -fPIC \
>  	 -I$(TOPDIR) \
>  	 -I$(TOPDIR)/kernel-lib \
> +	 -I$(TOPDIR)/libbtrfsutil \
>  	 $(EXTRAWARN_CFLAGS) \
>  	 $(DEBUG_CFLAGS_INTERNAL) \
>  	 $(EXTRA_CFLAGS)
>  
> +LIBBTRFSUTIL_CFLAGS = $(SUBST_CFLAGS) \
> +		      $(CSTD) \
> +		      -D_GNU_SOURCE \
> +		      -fPIC \
> +		      -fvisibility=hidden \
> +		      -I$(TOPDIR)/libbtrfsutil \
> +		      $(EXTRAWARN_CFLAGS) \
> +		      $(EXTRA_CFLAGS)
> +
>  LDFLAGS = $(SUBST_LDFLAGS) \
>  	  -rdynamic -L$(TOPDIR) \
>  	  $(DEBUG_LDFLAGS_INTERNAL) \
> @@ -121,12 +131,17 @@ libbtrfs_headers = send-stream.h send-utils.h send.h kernel-lib/rbtree.h btrfs-l
>  	       kernel-lib/crc32c.h kernel-lib/list.h kerncompat.h \
>  	       kernel-lib/radix-tree.h kernel-lib/sizes.h kernel-lib/raid56.h \
>  	       extent-cache.h extent_io.h ioctl.h ctree.h btrfsck.h version.h
> +libbtrfsutil_major := $(shell sed -rn 's/^\#define BTRFS_UTIL_VERSION_MAJOR ([0-9])+$$/\1/p' libbtrfsutil/btrfsutil.h)
> +libbtrfsutil_minor := $(shell sed -rn 's/^\#define BTRFS_UTIL_VERSION_MINOR ([0-9])+$$/\1/p' libbtrfsutil/btrfsutil.h)
> +libbtrfsutil_patch := $(shell sed -rn 's/^\#define BTRFS_UTIL_VERSION_PATCH ([0-9])+$$/\1/p' libbtrfsutil/btrfsutil.h)
> +libbtrfsutil_version := $(libbtrfsutil_major).$(libbtrfsutil_minor).$(libbtrfsutil_patch)
> +libbtrfsutil_objects = libbtrfsutil/errors.o
>  convert_objects = convert/main.o convert/common.o convert/source-fs.o \
>  		  convert/source-ext2.o convert/source-reiserfs.o
>  mkfs_objects = mkfs/main.o mkfs/common.o mkfs/rootdir.o
>  image_objects = image/main.o image/sanitize.o
>  all_objects = $(objects) $(cmds_objects) $(libbtrfs_objects) $(convert_objects) \
> -	      $(mkfs_objects) $(image_objects)
> +	      $(mkfs_objects) $(image_objects) $(libbtrfsutil_objects)
>  
>  udev_rules = 64-btrfs-dm.rules
>  
> @@ -246,11 +261,10 @@ static_convert_objects = $(patsubst %.o, %.static.o, $(convert_objects))
>  static_mkfs_objects = $(patsubst %.o, %.static.o, $(mkfs_objects))
>  static_image_objects = $(patsubst %.o, %.static.o, $(image_objects))
>  
> -libs_shared = libbtrfs.so.0.1
> -libs_static = libbtrfs.a
> +libs_shared = libbtrfs.so.0.1 libbtrfsutil.so.$(libbtrfsutil_version)
> +libs_static = libbtrfs.a libbtrfsutil.a
>  libs = $(libs_shared) $(libs_static)
> -lib_links = libbtrfs.so.0 libbtrfs.so
> -headers = $(libbtrfs_headers)
> +lib_links = libbtrfs.so.0 libbtrfs.so libbtrfsutil.so.$(libbtrfsutil_major) libbtrfsutil.so
>  
>  # make C=1 to enable sparse
>  ifdef C
> @@ -287,7 +301,7 @@ endif
>  	$(Q)$(CC) $(STATIC_CFLAGS) -c $< -o $@ $($(subst -,_,$(@:%.static.o=%)-cflags)) \
>  		$($(subst -,_,btrfs-$(@:%/$(notdir $@)=%)-cflags))
>  
> -all: $(progs) libbtrfs $(BUILDDIRS)
> +all: $(progs) $(libs) $(lib_links) $(BUILDDIRS)
>  $(SUBDIRS): $(BUILDDIRS)
>  $(BUILDDIRS):
>  	@echo "Making all in $(patsubst build-%,%,$@)"
> @@ -351,20 +365,35 @@ kernel-lib/tables.c:
>  	@echo "    [TABLE]  $@"
>  	$(Q)./mktables > $@ || ($(RM) -f $@ && exit 1)
>  
> -libbtrfs: $(libs_shared) $(lib_links)
> +libbtrfs.so.0.1: $(libbtrfs_objects)
> +	@echo "    [LD]     $@"
> +	$(Q)$(CC) $(CFLAGS) $^ $(LDFLAGS) $(LIBBTRFS_LIBS) \
> +		-shared -Wl,-soname,libbtrfs.so.0 -o $@
> +
> +libbtrfs.a: $(libbtrfs_objects)
> +	@echo "    [AR]     $@"
> +	$(Q)$(AR) cr $@ $^
> +
> +libbtrfs.so.0 libbtrfs.so: libbtrfs.so.0.1
> +	@echo "    [LN]     $@"
> +	$(Q)$(LN_S) -f $< $@
> +
> +libbtrfsutil/%.o: libbtrfsutil/%.c
> +	@echo "    [CC]     $@"
> +	$(Q)$(CC) $(LIBBTRFSUTIL_CFLAGS) -o $@ -c $< -o $@
>  
> -$(libs_shared): $(libbtrfs_objects) $(lib_links) send.h
> +libbtrfsutil.so.$(libbtrfsutil_version): $(libbtrfsutil_objects)
>  	@echo "    [LD]     $@"
> -	$(Q)$(CC) $(CFLAGS) $(libbtrfs_objects) $(LDFLAGS) $(LIBBTRFS_LIBS) \
> -		-shared -Wl,-soname,libbtrfs.so.0 -o libbtrfs.so.0.1
> +	$(Q)$(CC) $(LIBBTRFSUTIL_CFLAGS) $(libbtrfsutil_objects) \
> +		-shared -Wl,-soname,libbtrfsutil.so.$(libbtrfsutil_major) -o $@
>  
> -$(libs_static): $(libbtrfs_objects)
> +libbtrfsutil.a: $(libbtrfsutil_objects)
>  	@echo "    [AR]     $@"
> -	$(Q)$(AR) cr libbtrfs.a $(libbtrfs_objects)
> +	$(Q)$(AR) cr $@ $^
>  
> -$(lib_links):
> +libbtrfsutil.so.$(libbtrfsutil_major) libbtrfsutil.so: libbtrfsutil.so.$(libbtrfsutil_version)
>  	@echo "    [LN]     $@"
> -	$(Q)$(LN_S) -f libbtrfs.so.0.1 $@
> +	$(Q)$(LN_S) -f $< $@
>  
>  # keep intermediate files from the below implicit rules around
>  .PRECIOUS: $(addsuffix .o,$(progs))
> @@ -483,7 +512,7 @@ test-ioctl: ioctl-test ioctl-test-32 ioctl-test-64
>  	$(Q)./ioctl-test-32 > ioctl-test-32.log
>  	$(Q)./ioctl-test-64 > ioctl-test-64.log
>  
> -library-test: library-test.c $(libs_shared)
> +library-test: library-test.c libbtrfs.so
>  	@echo "    [TEST PREP]  $@"$(eval TMPD=$(shell mktemp -d))
>  	$(Q)mkdir -p $(TMPD)/include/btrfs && \
>  	cp $(libbtrfs_headers) $(TMPD)/include/btrfs && \
> @@ -547,7 +576,8 @@ clean: $(CLEANDIRS)
>                mktables btrfs.static mkfs.btrfs.static fssum \
>  	      $(check_defs) \
>  	      $(libs) $(lib_links) \
> -	      $(progs_static) $(progs_extra)
> +	      $(progs_static) $(progs_extra) \
> +	      libbtrfsutil/*.o libbtrfsutil/*.o.d
>  
>  clean-doc:
>  	@echo "Cleaning Documentation"
> @@ -575,8 +605,9 @@ install: $(libs) $(progs_install) $(INSTALLDIRS)
>  	$(INSTALL) -m755 -d $(DESTDIR)$(libdir)
>  	$(INSTALL) $(libs) $(DESTDIR)$(libdir)
>  	cp -a $(lib_links) $(DESTDIR)$(libdir)
> -	$(INSTALL) -m755 -d $(DESTDIR)$(incdir)
> -	$(INSTALL) -m644 $(headers) $(DESTDIR)$(incdir)
> +	$(INSTALL) -m755 -d $(DESTDIR)$(incdir)/btrfs
> +	$(INSTALL) -m644 $(libbtrfs_headers) $(DESTDIR)$(incdir)/btrfs
> +	$(INSTALL) -m644 libbtrfsutil/btrfsutil.h $(DESTDIR)$(incdir)
>  ifneq ($(udevdir),)
>  	$(INSTALL) -m755 -d $(DESTDIR)$(udevruledir)
>  	$(INSTALL) -m644 $(udev_rules) $(DESTDIR)$(udevruledir)
> @@ -594,8 +625,9 @@ $(INSTALLDIRS):
>  
>  uninstall:
>  	$(Q)$(MAKE) $(MAKEOPTS) -C Documentation uninstall
> -	cd $(DESTDIR)$(incdir); $(RM) -f -- $(headers)
> -	$(RMDIR) -p --ignore-fail-on-non-empty -- $(DESTDIR)$(incdir)
> +	cd $(DESTDIR)$(incdir)/btrfs; $(RM) -f -- $(libbtrfs_headers)
> +	$(RMDIR) -p --ignore-fail-on-non-empty -- $(DESTDIR)$(incdir)/btrfs
> +	cd $(DESTDIR)$(incdir); $(RM) -f -- btrfsutil.h
>  	cd $(DESTDIR)$(libdir); $(RM) -f -- $(lib_links) $(libs)
>  	cd $(DESTDIR)$(bindir); $(RM) -f -- btrfsck fsck.btrfs $(progs_install)
>  
> diff --git a/Makefile.inc.in b/Makefile.inc.in
> index 56271903..b53bef80 100644
> --- a/Makefile.inc.in
> +++ b/Makefile.inc.in
> @@ -27,7 +27,7 @@ prefix ?= @prefix@
>  exec_prefix = @exec_prefix@
>  bindir = @bindir@
>  libdir ?= @libdir@
> -incdir = @includedir@/btrfs
> +incdir = @includedir@
>  udevdir = @UDEVDIR@
>  udevruledir = ${udevdir}/rules.d
>  
> diff --git a/libbtrfsutil/COPYING b/libbtrfsutil/COPYING
> new file mode 100644
> index 00000000..f288702d
> --- /dev/null
> +++ b/libbtrfsutil/COPYING
> @@ -0,0 +1,674 @@
> +                    GNU GENERAL PUBLIC LICENSE
> +                       Version 3, 29 June 2007
> +
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> + Everyone is permitted to copy and distribute verbatim copies
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> +Also add information on how to contact you by electronic and paper mail.
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> +    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
> +    This is free software, and you are welcome to redistribute it
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> +
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> diff --git a/libbtrfsutil/COPYING.LESSER b/libbtrfsutil/COPYING.LESSER
> new file mode 100644
> index 00000000..0a041280
> --- /dev/null
> +++ b/libbtrfsutil/COPYING.LESSER
> @@ -0,0 +1,165 @@
> +                   GNU LESSER GENERAL PUBLIC LICENSE
> +                       Version 3, 29 June 2007
> +
> + Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
> + Everyone is permitted to copy and distribute verbatim copies
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> +
> +  This version of the GNU Lesser General Public License incorporates
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> +  0. Additional Definitions.
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> +       suitable for, and under terms that permit, the user to
> +       recombine or relink the Application with a modified version of
> +       the Linked Version to produce a modified Combined Work, in the
> +       manner specified by section 6 of the GNU GPL for conveying
> +       Corresponding Source.
> +
> +       1) Use a suitable shared library mechanism for linking with the
> +       Library.  A suitable mechanism is one that (a) uses at run time
> +       a copy of the Library already present on the user's computer
> +       system, and (b) will operate properly with a modified version
> +       of the Library that is interface-compatible with the Linked
> +       Version.
> +
> +   e) Provide Installation Information, but only if you would otherwise
> +   be required to provide such information under section 6 of the
> +   GNU GPL, and only to the extent that such information is
> +   necessary to install and execute a modified version of the
> +   Combined Work produced by recombining or relinking the
> +   Application with a modified version of the Linked Version. (If
> +   you use option 4d0, the Installation Information must accompany
> +   the Minimal Corresponding Source and Corresponding Application
> +   Code. If you use option 4d1, you must provide the Installation
> +   Information in the manner specified by section 6 of the GNU GPL
> +   for conveying Corresponding Source.)
> +
> +  5. Combined Libraries.
> +
> +  You may place library facilities that are a work based on the
> +Library side by side in a single library together with other library
> +facilities that are not Applications and are not covered by this
> +License, and convey such a combined library under terms of your
> +choice, if you do both of the following:
> +
> +   a) Accompany the combined library with a copy of the same work based
> +   on the Library, uncombined with any other library facilities,
> +   conveyed under the terms of this License.
> +
> +   b) Give prominent notice with the combined library that part of it
> +   is a work based on the Library, and explaining where to find the
> +   accompanying uncombined form of the same work.
> +
> +  6. Revised Versions of the GNU Lesser General Public License.
> +
> +  The Free Software Foundation may publish revised and/or new versions
> +of the GNU Lesser General Public License from time to time. Such new
> +versions will be similar in spirit to the present version, but may
> +differ in detail to address new problems or concerns.
> +
> +  Each version is given a distinguishing version number. If the
> +Library as you received it specifies that a certain numbered version
> +of the GNU Lesser General Public License "or any later version"
> +applies to it, you have the option of following the terms and
> +conditions either of that published version or of any later version
> +published by the Free Software Foundation. If the Library as you
> +received it does not specify a version number of the GNU Lesser
> +General Public License, you may choose any version of the GNU Lesser
> +General Public License ever published by the Free Software Foundation.
> +
> +  If the Library as you received it specifies that a proxy can decide
> +whether future versions of the GNU Lesser General Public License shall
> +apply, that proxy's public statement of acceptance of any version is
> +permanent authorization for you to choose that version for the
> +Library.
> diff --git a/libbtrfsutil/README.md b/libbtrfsutil/README.md
> new file mode 100644
> index 00000000..ee4c6a1d
> --- /dev/null
> +++ b/libbtrfsutil/README.md
> @@ -0,0 +1,35 @@
> +libbtrfsutil
> +============
> +
> +libbtrfsutil is a library for managing Btrfs filesystems. It is licensed under
> +the LGPL. libbtrfsutil provides interfaces for a subset of the operations
> +offered by the `btrfs` command line utility.
> +
> +Development
> +-----------
> +
> +The [development process for btrfs-progs](../README.md#development) applies.
> +
> +libbtrfsutil only includes operations that are done through the filesystem and
> +ioctl interface, not operations that modify the filesystem directly (e.g., mkfs
> +or fsck). This is by design but also a legal necessity, as the filesystem
> +implementation is GPL but libbtrfsutil is LGPL. That is also why the
> +libbtrfsutil code is a reimplementation of the btrfs-progs code rather than a
> +refactoring. Be wary of this when porting functionality.
> +
> +libbtrfsutil is semantically versioned separately from btrfs-progs. It is the
> +maintainers' responsibility to bump the version as needed (at most once per
> +release of btrfs-progs).
> +
> +A few guidelines:
> +
> +* All interfaces must be documented in `btrfsutil.h` using the kernel-doc style
> +* Error codes should be specific about what _exactly_ failed
> +* Functions should have a path and an fd variant whenever possible
> +* Spell out terms in function names, etc. rather than abbreviating whenever
> +  possible
> +* Don't require the Btrfs UAPI headers for any interfaces (e.g., instead of
> +  directly exposing a type from `linux/btrfs_tree.h`, abstract it away in a
> +  type specific to `libbtrfsutil`)
> +* Preserve API and ABI compatability at all times (i.e., we don't want to bump
> +  the library major version if we don't have to)
> diff --git a/libbtrfsutil/btrfsutil.h b/libbtrfsutil/btrfsutil.h
> new file mode 100644
> index 00000000..867418f2
> --- /dev/null
> +++ b/libbtrfsutil/btrfsutil.h
> @@ -0,0 +1,76 @@
> +/*
> + * Copyright (C) 2018 Facebook
> + *
> + * This file is part of libbtrfsutil.
> + *
> + * libbtrfsutil is free software: you can redistribute it and/or modify
> + * it under the terms of the GNU Lesser General Public License as published by
> + * the Free Software Foundation, either version 3 of the License, or
> + * (at your option) any later version.
> + *
> + * libbtrfsutil is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public License
> + * along with libbtrfsutil.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef BTRFS_UTIL_H
> +#define BTRFS_UTIL_H
> +
> +#define BTRFS_UTIL_VERSION_MAJOR 1
> +#define BTRFS_UTIL_VERSION_MINOR 0
> +#define BTRFS_UTIL_VERSION_PATCH 0
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
> +/**
> + * enum btrfs_util_error - libbtrfsutil error codes.
> + *
> + * All functions in libbtrfsutil that can return an error return this type and
> + * set errno.
> + */
> +enum btrfs_util_error {
> +	BTRFS_UTIL_OK,
> +	BTRFS_UTIL_ERROR_STOP_ITERATION,
> +	BTRFS_UTIL_ERROR_NO_MEMORY,
> +	BTRFS_UTIL_ERROR_INVALID_ARGUMENT,
> +	BTRFS_UTIL_ERROR_NOT_BTRFS,
> +	BTRFS_UTIL_ERROR_NOT_SUBVOLUME,
> +	BTRFS_UTIL_ERROR_SUBVOLUME_NOT_FOUND,
> +	BTRFS_UTIL_ERROR_OPEN_FAILED,
> +	BTRFS_UTIL_ERROR_RMDIR_FAILED,
> +	BTRFS_UTIL_ERROR_UNLINK_FAILED,
> +	BTRFS_UTIL_ERROR_STAT_FAILED,
> +	BTRFS_UTIL_ERROR_STATFS_FAILED,
> +	BTRFS_UTIL_ERROR_SEARCH_FAILED,
> +	BTRFS_UTIL_ERROR_INO_LOOKUP_FAILED,
> +	BTRFS_UTIL_ERROR_SUBVOL_GETFLAGS_FAILED,
> +	BTRFS_UTIL_ERROR_SUBVOL_SETFLAGS_FAILED,
> +	BTRFS_UTIL_ERROR_SUBVOL_CREATE_FAILED,
> +	BTRFS_UTIL_ERROR_SNAP_CREATE_FAILED,
> +	BTRFS_UTIL_ERROR_SNAP_DESTROY_FAILED,
> +	BTRFS_UTIL_ERROR_DEFAULT_SUBVOL_FAILED,
> +	BTRFS_UTIL_ERROR_SYNC_FAILED,
> +	BTRFS_UTIL_ERROR_START_SYNC_FAILED,
> +	BTRFS_UTIL_ERROR_WAIT_SYNC_FAILED,
> +};
> +
> +/**
> + * btrfs_util_strerror() - Convert a libtrfsutil error code to a string
> + * description.
> + * @err: The error to convert.
> + *
> + * Return: Error description.
> + */
> +const char *btrfs_util_strerror(enum btrfs_util_error err);
> +
> +#ifdef __cplusplus
> +}
> +#endif
> +
> +#endif /* BTRFS_UTIL_H */
> diff --git a/libbtrfsutil/btrfsutil_internal.h b/libbtrfsutil/btrfsutil_internal.h
> new file mode 100644
> index 00000000..bdf8840a
> --- /dev/null
> +++ b/libbtrfsutil/btrfsutil_internal.h
> @@ -0,0 +1,40 @@
> +/*
> + * Copyright (C) 2018 Facebook
> + *
> + * This file is part of libbtrfsutil.
> + *
> + * libbtrfsutil is free software: you can redistribute it and/or modify
> + * it under the terms of the GNU Lesser General Public License as published by
> + * the Free Software Foundation, either version 3 of the License, or
> + * (at your option) any later version.
> + *
> + * libbtrfsutil is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public License
> + * along with libbtrfsutil.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef BTRFS_UTIL_INTERNAL_H
> +#define BTRFS_UTIL_INTERNAL_H
> +
> +#include <asm/byteorder.h>
> +
> +#include "btrfsutil.h"
> +
> +#define PUBLIC __attribute__((visibility("default")))
> +
> +#define le16_to_cpu __le16_to_cpu
> +#define le32_to_cpu __le32_to_cpu
> +#define le64_to_cpu __le64_to_cpu
> +
> +#define SAVE_ERRNO_AND_CLOSE(fd) {	\
> +	int saved_errno = errno;	\
> +					\
> +	close(fd);			\
> +	errno = saved_errno;		\
> +}
> +
> +#endif /* BTRFS_UTIL_INTERNAL_H */
> diff --git a/libbtrfsutil/errors.c b/libbtrfsutil/errors.c
> new file mode 100644
> index 00000000..634edc65
> --- /dev/null
> +++ b/libbtrfsutil/errors.c
> @@ -0,0 +1,55 @@
> +/*
> + * Copyright (C) 2018 Facebook
> + *
> + * This file is part of libbtrfsutil.
> + *
> + * libbtrfsutil is free software: you can redistribute it and/or modify
> + * it under the terms of the GNU Lesser General Public License as published by
> + * the Free Software Foundation, either version 3 of the License, or
> + * (at your option) any later version.
> + *
> + * libbtrfsutil is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public License
> + * along with libbtrfsutil.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <stddef.h>
> +
> +#include "btrfsutil_internal.h"
> +
> +static const char * const error_messages[] = {
> +	[BTRFS_UTIL_OK] = "Success",
> +	[BTRFS_UTIL_ERROR_STOP_ITERATION] = "Stop iteration",
> +	[BTRFS_UTIL_ERROR_NO_MEMORY] = "Cannot allocate memory",
> +	[BTRFS_UTIL_ERROR_INVALID_ARGUMENT] = "Invalid argument",
> +	[BTRFS_UTIL_ERROR_NOT_BTRFS] = "Not a Btrfs filesystem",
> +	[BTRFS_UTIL_ERROR_NOT_SUBVOLUME] = "Not a Btrfs subvolume",
> +	[BTRFS_UTIL_ERROR_SUBVOLUME_NOT_FOUND] = "Subvolume not found",
> +	[BTRFS_UTIL_ERROR_OPEN_FAILED] = "Could not open",
> +	[BTRFS_UTIL_ERROR_RMDIR_FAILED] = "Could not rmdir",
> +	[BTRFS_UTIL_ERROR_UNLINK_FAILED] = "Could not unlink",
> +	[BTRFS_UTIL_ERROR_STAT_FAILED] = "Could not stat",
> +	[BTRFS_UTIL_ERROR_STATFS_FAILED] = "Could not statfs",
> +	[BTRFS_UTIL_ERROR_SEARCH_FAILED] = "Could not search B-tree",
> +	[BTRFS_UTIL_ERROR_INO_LOOKUP_FAILED] = "Could not lookup inode",
> +	[BTRFS_UTIL_ERROR_SUBVOL_GETFLAGS_FAILED] = "Could not get subvolume flags",
> +	[BTRFS_UTIL_ERROR_SUBVOL_SETFLAGS_FAILED] = "Could not set subvolume flags",
> +	[BTRFS_UTIL_ERROR_SUBVOL_CREATE_FAILED] = "Could not create subvolume",
> +	[BTRFS_UTIL_ERROR_SNAP_CREATE_FAILED] = "Could not create snapshot",
> +	[BTRFS_UTIL_ERROR_SNAP_DESTROY_FAILED] = "Could not destroy subvolume/snapshot",
> +	[BTRFS_UTIL_ERROR_DEFAULT_SUBVOL_FAILED] = "Could not set default subvolume",
> +	[BTRFS_UTIL_ERROR_SYNC_FAILED] = "Could not sync filesystem",
> +	[BTRFS_UTIL_ERROR_START_SYNC_FAILED] = "Could not start filesystem sync",
> +	[BTRFS_UTIL_ERROR_WAIT_SYNC_FAILED] = "Could not wait for filesystem sync",
> +};
> +
> +PUBLIC const char *btrfs_util_strerror(enum btrfs_util_error err)
> +{
> +	if (err < 0 || err >= sizeof(error_messages) / sizeof(error_messages[0]))
> +		return NULL;
> +	return error_messages[err];
> +}
> -- 
> 2.16.1
> 
> --
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> the body of a message to majordomo@vger.kernel.org
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David Sterba Feb. 20, 2018, 6:34 p.m. UTC | #2
On Tue, Feb 20, 2018 at 10:32:17AM -0700, Liu Bo wrote:
> > --- a/.gitignore
> > +++ b/.gitignore
> > @@ -43,6 +43,8 @@ libbtrfs.so.0.1
> >  library-test
> >  library-test-static
> >  /fssum
> > +/libbtrfsutil.so*
> > +/libbtrfsutil.a
> 
> .gitignore is not part of btrfs-progs, is it?

It is, since version 0.19 :)
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diff mbox

Patch

diff --git a/.gitignore b/.gitignore
index 8e607f6e..272d53e4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -43,6 +43,8 @@  libbtrfs.so.0.1
 library-test
 library-test-static
 /fssum
+/libbtrfsutil.so*
+/libbtrfsutil.a
 
 /tests/*-tests-results.txt
 /tests/test-console.txt
diff --git a/Makefile b/Makefile
index 00e21379..7fb70d06 100644
--- a/Makefile
+++ b/Makefile
@@ -73,10 +73,20 @@  CFLAGS = $(SUBST_CFLAGS) \
 	 -fPIC \
 	 -I$(TOPDIR) \
 	 -I$(TOPDIR)/kernel-lib \
+	 -I$(TOPDIR)/libbtrfsutil \
 	 $(EXTRAWARN_CFLAGS) \
 	 $(DEBUG_CFLAGS_INTERNAL) \
 	 $(EXTRA_CFLAGS)
 
+LIBBTRFSUTIL_CFLAGS = $(SUBST_CFLAGS) \
+		      $(CSTD) \
+		      -D_GNU_SOURCE \
+		      -fPIC \
+		      -fvisibility=hidden \
+		      -I$(TOPDIR)/libbtrfsutil \
+		      $(EXTRAWARN_CFLAGS) \
+		      $(EXTRA_CFLAGS)
+
 LDFLAGS = $(SUBST_LDFLAGS) \
 	  -rdynamic -L$(TOPDIR) \
 	  $(DEBUG_LDFLAGS_INTERNAL) \
@@ -121,12 +131,17 @@  libbtrfs_headers = send-stream.h send-utils.h send.h kernel-lib/rbtree.h btrfs-l
 	       kernel-lib/crc32c.h kernel-lib/list.h kerncompat.h \
 	       kernel-lib/radix-tree.h kernel-lib/sizes.h kernel-lib/raid56.h \
 	       extent-cache.h extent_io.h ioctl.h ctree.h btrfsck.h version.h
+libbtrfsutil_major := $(shell sed -rn 's/^\#define BTRFS_UTIL_VERSION_MAJOR ([0-9])+$$/\1/p' libbtrfsutil/btrfsutil.h)
+libbtrfsutil_minor := $(shell sed -rn 's/^\#define BTRFS_UTIL_VERSION_MINOR ([0-9])+$$/\1/p' libbtrfsutil/btrfsutil.h)
+libbtrfsutil_patch := $(shell sed -rn 's/^\#define BTRFS_UTIL_VERSION_PATCH ([0-9])+$$/\1/p' libbtrfsutil/btrfsutil.h)
+libbtrfsutil_version := $(libbtrfsutil_major).$(libbtrfsutil_minor).$(libbtrfsutil_patch)
+libbtrfsutil_objects = libbtrfsutil/errors.o
 convert_objects = convert/main.o convert/common.o convert/source-fs.o \
 		  convert/source-ext2.o convert/source-reiserfs.o
 mkfs_objects = mkfs/main.o mkfs/common.o mkfs/rootdir.o
 image_objects = image/main.o image/sanitize.o
 all_objects = $(objects) $(cmds_objects) $(libbtrfs_objects) $(convert_objects) \
-	      $(mkfs_objects) $(image_objects)
+	      $(mkfs_objects) $(image_objects) $(libbtrfsutil_objects)
 
 udev_rules = 64-btrfs-dm.rules
 
@@ -246,11 +261,10 @@  static_convert_objects = $(patsubst %.o, %.static.o, $(convert_objects))
 static_mkfs_objects = $(patsubst %.o, %.static.o, $(mkfs_objects))
 static_image_objects = $(patsubst %.o, %.static.o, $(image_objects))
 
-libs_shared = libbtrfs.so.0.1
-libs_static = libbtrfs.a
+libs_shared = libbtrfs.so.0.1 libbtrfsutil.so.$(libbtrfsutil_version)
+libs_static = libbtrfs.a libbtrfsutil.a
 libs = $(libs_shared) $(libs_static)
-lib_links = libbtrfs.so.0 libbtrfs.so
-headers = $(libbtrfs_headers)
+lib_links = libbtrfs.so.0 libbtrfs.so libbtrfsutil.so.$(libbtrfsutil_major) libbtrfsutil.so
 
 # make C=1 to enable sparse
 ifdef C
@@ -287,7 +301,7 @@  endif
 	$(Q)$(CC) $(STATIC_CFLAGS) -c $< -o $@ $($(subst -,_,$(@:%.static.o=%)-cflags)) \
 		$($(subst -,_,btrfs-$(@:%/$(notdir $@)=%)-cflags))
 
-all: $(progs) libbtrfs $(BUILDDIRS)
+all: $(progs) $(libs) $(lib_links) $(BUILDDIRS)
 $(SUBDIRS): $(BUILDDIRS)
 $(BUILDDIRS):
 	@echo "Making all in $(patsubst build-%,%,$@)"
@@ -351,20 +365,35 @@  kernel-lib/tables.c:
 	@echo "    [TABLE]  $@"
 	$(Q)./mktables > $@ || ($(RM) -f $@ && exit 1)
 
-libbtrfs: $(libs_shared) $(lib_links)
+libbtrfs.so.0.1: $(libbtrfs_objects)
+	@echo "    [LD]     $@"
+	$(Q)$(CC) $(CFLAGS) $^ $(LDFLAGS) $(LIBBTRFS_LIBS) \
+		-shared -Wl,-soname,libbtrfs.so.0 -o $@
+
+libbtrfs.a: $(libbtrfs_objects)
+	@echo "    [AR]     $@"
+	$(Q)$(AR) cr $@ $^
+
+libbtrfs.so.0 libbtrfs.so: libbtrfs.so.0.1
+	@echo "    [LN]     $@"
+	$(Q)$(LN_S) -f $< $@
+
+libbtrfsutil/%.o: libbtrfsutil/%.c
+	@echo "    [CC]     $@"
+	$(Q)$(CC) $(LIBBTRFSUTIL_CFLAGS) -o $@ -c $< -o $@
 
-$(libs_shared): $(libbtrfs_objects) $(lib_links) send.h
+libbtrfsutil.so.$(libbtrfsutil_version): $(libbtrfsutil_objects)
 	@echo "    [LD]     $@"
-	$(Q)$(CC) $(CFLAGS) $(libbtrfs_objects) $(LDFLAGS) $(LIBBTRFS_LIBS) \
-		-shared -Wl,-soname,libbtrfs.so.0 -o libbtrfs.so.0.1
+	$(Q)$(CC) $(LIBBTRFSUTIL_CFLAGS) $(libbtrfsutil_objects) \
+		-shared -Wl,-soname,libbtrfsutil.so.$(libbtrfsutil_major) -o $@
 
-$(libs_static): $(libbtrfs_objects)
+libbtrfsutil.a: $(libbtrfsutil_objects)
 	@echo "    [AR]     $@"
-	$(Q)$(AR) cr libbtrfs.a $(libbtrfs_objects)
+	$(Q)$(AR) cr $@ $^
 
-$(lib_links):
+libbtrfsutil.so.$(libbtrfsutil_major) libbtrfsutil.so: libbtrfsutil.so.$(libbtrfsutil_version)
 	@echo "    [LN]     $@"
-	$(Q)$(LN_S) -f libbtrfs.so.0.1 $@
+	$(Q)$(LN_S) -f $< $@
 
 # keep intermediate files from the below implicit rules around
 .PRECIOUS: $(addsuffix .o,$(progs))
@@ -483,7 +512,7 @@  test-ioctl: ioctl-test ioctl-test-32 ioctl-test-64
 	$(Q)./ioctl-test-32 > ioctl-test-32.log
 	$(Q)./ioctl-test-64 > ioctl-test-64.log
 
-library-test: library-test.c $(libs_shared)
+library-test: library-test.c libbtrfs.so
 	@echo "    [TEST PREP]  $@"$(eval TMPD=$(shell mktemp -d))
 	$(Q)mkdir -p $(TMPD)/include/btrfs && \
 	cp $(libbtrfs_headers) $(TMPD)/include/btrfs && \
@@ -547,7 +576,8 @@  clean: $(CLEANDIRS)
               mktables btrfs.static mkfs.btrfs.static fssum \
 	      $(check_defs) \
 	      $(libs) $(lib_links) \
-	      $(progs_static) $(progs_extra)
+	      $(progs_static) $(progs_extra) \
+	      libbtrfsutil/*.o libbtrfsutil/*.o.d
 
 clean-doc:
 	@echo "Cleaning Documentation"
@@ -575,8 +605,9 @@  install: $(libs) $(progs_install) $(INSTALLDIRS)
 	$(INSTALL) -m755 -d $(DESTDIR)$(libdir)
 	$(INSTALL) $(libs) $(DESTDIR)$(libdir)
 	cp -a $(lib_links) $(DESTDIR)$(libdir)
-	$(INSTALL) -m755 -d $(DESTDIR)$(incdir)
-	$(INSTALL) -m644 $(headers) $(DESTDIR)$(incdir)
+	$(INSTALL) -m755 -d $(DESTDIR)$(incdir)/btrfs
+	$(INSTALL) -m644 $(libbtrfs_headers) $(DESTDIR)$(incdir)/btrfs
+	$(INSTALL) -m644 libbtrfsutil/btrfsutil.h $(DESTDIR)$(incdir)
 ifneq ($(udevdir),)
 	$(INSTALL) -m755 -d $(DESTDIR)$(udevruledir)
 	$(INSTALL) -m644 $(udev_rules) $(DESTDIR)$(udevruledir)
@@ -594,8 +625,9 @@  $(INSTALLDIRS):
 
 uninstall:
 	$(Q)$(MAKE) $(MAKEOPTS) -C Documentation uninstall
-	cd $(DESTDIR)$(incdir); $(RM) -f -- $(headers)
-	$(RMDIR) -p --ignore-fail-on-non-empty -- $(DESTDIR)$(incdir)
+	cd $(DESTDIR)$(incdir)/btrfs; $(RM) -f -- $(libbtrfs_headers)
+	$(RMDIR) -p --ignore-fail-on-non-empty -- $(DESTDIR)$(incdir)/btrfs
+	cd $(DESTDIR)$(incdir); $(RM) -f -- btrfsutil.h
 	cd $(DESTDIR)$(libdir); $(RM) -f -- $(lib_links) $(libs)
 	cd $(DESTDIR)$(bindir); $(RM) -f -- btrfsck fsck.btrfs $(progs_install)
 
diff --git a/Makefile.inc.in b/Makefile.inc.in
index 56271903..b53bef80 100644
--- a/Makefile.inc.in
+++ b/Makefile.inc.in
@@ -27,7 +27,7 @@  prefix ?= @prefix@
 exec_prefix = @exec_prefix@
 bindir = @bindir@
 libdir ?= @libdir@
-incdir = @includedir@/btrfs
+incdir = @includedir@
 udevdir = @UDEVDIR@
 udevruledir = ${udevdir}/rules.d
 
diff --git a/libbtrfsutil/COPYING b/libbtrfsutil/COPYING
new file mode 100644
index 00000000..f288702d
--- /dev/null
+++ b/libbtrfsutil/COPYING
@@ -0,0 +1,674 @@ 
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
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+  17. Interpretation of Sections 15 and 16.
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+  If the disclaimer of warranty and limitation of liability provided
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+                     END OF TERMS AND CONDITIONS
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+  If you develop a new program, and you want it to be of the greatest
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+  To do so, attach the following notices to the program.  It is safest
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+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
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+
+Also add information on how to contact you by electronic and paper mail.
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+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
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+
+The hypothetical commands `show w' and `show c' should show the appropriate
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+  You should also get your employer (if you work as a programmer) or school,
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+For more information on this, and how to apply and follow the GNU GPL, see
+<https://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.
diff --git a/libbtrfsutil/COPYING.LESSER b/libbtrfsutil/COPYING.LESSER
new file mode 100644
index 00000000..0a041280
--- /dev/null
+++ b/libbtrfsutil/COPYING.LESSER
@@ -0,0 +1,165 @@ 
+                   GNU LESSER GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+
+  This version of the GNU Lesser General Public License incorporates
+the terms and conditions of version 3 of the GNU General Public
+License, supplemented by the additional permissions listed below.
+
+  0. Additional Definitions.
+
+  As used herein, "this License" refers to version 3 of the GNU Lesser
+General Public License, and the "GNU GPL" refers to version 3 of the GNU
+General Public License.
+
+  "The Library" refers to a covered work governed by this License,
+other than an Application or a Combined Work as defined below.
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+   a) Give prominent notice with each copy of the object code that the
+   Library is used in it and that the Library and its use are
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+  4. Combined Works.
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+  You may convey a Combined Work under terms of your choice that,
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+  If the Library as you received it specifies that a proxy can decide
+whether future versions of the GNU Lesser General Public License shall
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+Library.
diff --git a/libbtrfsutil/README.md b/libbtrfsutil/README.md
new file mode 100644
index 00000000..ee4c6a1d
--- /dev/null
+++ b/libbtrfsutil/README.md
@@ -0,0 +1,35 @@ 
+libbtrfsutil
+============
+
+libbtrfsutil is a library for managing Btrfs filesystems. It is licensed under
+the LGPL. libbtrfsutil provides interfaces for a subset of the operations
+offered by the `btrfs` command line utility.
+
+Development
+-----------
+
+The [development process for btrfs-progs](../README.md#development) applies.
+
+libbtrfsutil only includes operations that are done through the filesystem and
+ioctl interface, not operations that modify the filesystem directly (e.g., mkfs
+or fsck). This is by design but also a legal necessity, as the filesystem
+implementation is GPL but libbtrfsutil is LGPL. That is also why the
+libbtrfsutil code is a reimplementation of the btrfs-progs code rather than a
+refactoring. Be wary of this when porting functionality.
+
+libbtrfsutil is semantically versioned separately from btrfs-progs. It is the
+maintainers' responsibility to bump the version as needed (at most once per
+release of btrfs-progs).
+
+A few guidelines:
+
+* All interfaces must be documented in `btrfsutil.h` using the kernel-doc style
+* Error codes should be specific about what _exactly_ failed
+* Functions should have a path and an fd variant whenever possible
+* Spell out terms in function names, etc. rather than abbreviating whenever
+  possible
+* Don't require the Btrfs UAPI headers for any interfaces (e.g., instead of
+  directly exposing a type from `linux/btrfs_tree.h`, abstract it away in a
+  type specific to `libbtrfsutil`)
+* Preserve API and ABI compatability at all times (i.e., we don't want to bump
+  the library major version if we don't have to)
diff --git a/libbtrfsutil/btrfsutil.h b/libbtrfsutil/btrfsutil.h
new file mode 100644
index 00000000..867418f2
--- /dev/null
+++ b/libbtrfsutil/btrfsutil.h
@@ -0,0 +1,76 @@ 
+/*
+ * Copyright (C) 2018 Facebook
+ *
+ * This file is part of libbtrfsutil.
+ *
+ * libbtrfsutil is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * libbtrfsutil is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with libbtrfsutil.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef BTRFS_UTIL_H
+#define BTRFS_UTIL_H
+
+#define BTRFS_UTIL_VERSION_MAJOR 1
+#define BTRFS_UTIL_VERSION_MINOR 0
+#define BTRFS_UTIL_VERSION_PATCH 0
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * enum btrfs_util_error - libbtrfsutil error codes.
+ *
+ * All functions in libbtrfsutil that can return an error return this type and
+ * set errno.
+ */
+enum btrfs_util_error {
+	BTRFS_UTIL_OK,
+	BTRFS_UTIL_ERROR_STOP_ITERATION,
+	BTRFS_UTIL_ERROR_NO_MEMORY,
+	BTRFS_UTIL_ERROR_INVALID_ARGUMENT,
+	BTRFS_UTIL_ERROR_NOT_BTRFS,
+	BTRFS_UTIL_ERROR_NOT_SUBVOLUME,
+	BTRFS_UTIL_ERROR_SUBVOLUME_NOT_FOUND,
+	BTRFS_UTIL_ERROR_OPEN_FAILED,
+	BTRFS_UTIL_ERROR_RMDIR_FAILED,
+	BTRFS_UTIL_ERROR_UNLINK_FAILED,
+	BTRFS_UTIL_ERROR_STAT_FAILED,
+	BTRFS_UTIL_ERROR_STATFS_FAILED,
+	BTRFS_UTIL_ERROR_SEARCH_FAILED,
+	BTRFS_UTIL_ERROR_INO_LOOKUP_FAILED,
+	BTRFS_UTIL_ERROR_SUBVOL_GETFLAGS_FAILED,
+	BTRFS_UTIL_ERROR_SUBVOL_SETFLAGS_FAILED,
+	BTRFS_UTIL_ERROR_SUBVOL_CREATE_FAILED,
+	BTRFS_UTIL_ERROR_SNAP_CREATE_FAILED,
+	BTRFS_UTIL_ERROR_SNAP_DESTROY_FAILED,
+	BTRFS_UTIL_ERROR_DEFAULT_SUBVOL_FAILED,
+	BTRFS_UTIL_ERROR_SYNC_FAILED,
+	BTRFS_UTIL_ERROR_START_SYNC_FAILED,
+	BTRFS_UTIL_ERROR_WAIT_SYNC_FAILED,
+};
+
+/**
+ * btrfs_util_strerror() - Convert a libtrfsutil error code to a string
+ * description.
+ * @err: The error to convert.
+ *
+ * Return: Error description.
+ */
+const char *btrfs_util_strerror(enum btrfs_util_error err);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BTRFS_UTIL_H */
diff --git a/libbtrfsutil/btrfsutil_internal.h b/libbtrfsutil/btrfsutil_internal.h
new file mode 100644
index 00000000..bdf8840a
--- /dev/null
+++ b/libbtrfsutil/btrfsutil_internal.h
@@ -0,0 +1,40 @@ 
+/*
+ * Copyright (C) 2018 Facebook
+ *
+ * This file is part of libbtrfsutil.
+ *
+ * libbtrfsutil is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * libbtrfsutil is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with libbtrfsutil.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef BTRFS_UTIL_INTERNAL_H
+#define BTRFS_UTIL_INTERNAL_H
+
+#include <asm/byteorder.h>
+
+#include "btrfsutil.h"
+
+#define PUBLIC __attribute__((visibility("default")))
+
+#define le16_to_cpu __le16_to_cpu
+#define le32_to_cpu __le32_to_cpu
+#define le64_to_cpu __le64_to_cpu
+
+#define SAVE_ERRNO_AND_CLOSE(fd) {	\
+	int saved_errno = errno;	\
+					\
+	close(fd);			\
+	errno = saved_errno;		\
+}
+
+#endif /* BTRFS_UTIL_INTERNAL_H */
diff --git a/libbtrfsutil/errors.c b/libbtrfsutil/errors.c
new file mode 100644
index 00000000..634edc65
--- /dev/null
+++ b/libbtrfsutil/errors.c
@@ -0,0 +1,55 @@ 
+/*
+ * Copyright (C) 2018 Facebook
+ *
+ * This file is part of libbtrfsutil.
+ *
+ * libbtrfsutil is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * libbtrfsutil is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with libbtrfsutil.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stddef.h>
+
+#include "btrfsutil_internal.h"
+
+static const char * const error_messages[] = {
+	[BTRFS_UTIL_OK] = "Success",
+	[BTRFS_UTIL_ERROR_STOP_ITERATION] = "Stop iteration",
+	[BTRFS_UTIL_ERROR_NO_MEMORY] = "Cannot allocate memory",
+	[BTRFS_UTIL_ERROR_INVALID_ARGUMENT] = "Invalid argument",
+	[BTRFS_UTIL_ERROR_NOT_BTRFS] = "Not a Btrfs filesystem",
+	[BTRFS_UTIL_ERROR_NOT_SUBVOLUME] = "Not a Btrfs subvolume",
+	[BTRFS_UTIL_ERROR_SUBVOLUME_NOT_FOUND] = "Subvolume not found",
+	[BTRFS_UTIL_ERROR_OPEN_FAILED] = "Could not open",
+	[BTRFS_UTIL_ERROR_RMDIR_FAILED] = "Could not rmdir",
+	[BTRFS_UTIL_ERROR_UNLINK_FAILED] = "Could not unlink",
+	[BTRFS_UTIL_ERROR_STAT_FAILED] = "Could not stat",
+	[BTRFS_UTIL_ERROR_STATFS_FAILED] = "Could not statfs",
+	[BTRFS_UTIL_ERROR_SEARCH_FAILED] = "Could not search B-tree",
+	[BTRFS_UTIL_ERROR_INO_LOOKUP_FAILED] = "Could not lookup inode",
+	[BTRFS_UTIL_ERROR_SUBVOL_GETFLAGS_FAILED] = "Could not get subvolume flags",
+	[BTRFS_UTIL_ERROR_SUBVOL_SETFLAGS_FAILED] = "Could not set subvolume flags",
+	[BTRFS_UTIL_ERROR_SUBVOL_CREATE_FAILED] = "Could not create subvolume",
+	[BTRFS_UTIL_ERROR_SNAP_CREATE_FAILED] = "Could not create snapshot",
+	[BTRFS_UTIL_ERROR_SNAP_DESTROY_FAILED] = "Could not destroy subvolume/snapshot",
+	[BTRFS_UTIL_ERROR_DEFAULT_SUBVOL_FAILED] = "Could not set default subvolume",
+	[BTRFS_UTIL_ERROR_SYNC_FAILED] = "Could not sync filesystem",
+	[BTRFS_UTIL_ERROR_START_SYNC_FAILED] = "Could not start filesystem sync",
+	[BTRFS_UTIL_ERROR_WAIT_SYNC_FAILED] = "Could not wait for filesystem sync",
+};
+
+PUBLIC const char *btrfs_util_strerror(enum btrfs_util_error err)
+{
+	if (err < 0 || err >= sizeof(error_messages) / sizeof(error_messages[0]))
+		return NULL;
+	return error_messages[err];
+}