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From: Omar Sandoval <osandov@osandov.com>
To: linux-btrfs@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Subject: [PATCH 05/11] btrfs-progs: receive: add stub implementation for pwritev2
Date: Fri, 21 Aug 2020 00:40:04 -0700	[thread overview]
Message-ID: <fa0a8010abb91862ffd90a3d19fd63c14b28b98f.1597994354.git.osandov@osandov.com> (raw)
In-Reply-To: <cover.1597994106.git.osandov@osandov.com>

From: Boris Burkov <borisb@fb.com>

Encoded writes in receive will use pwritev2. It is possible that the
system libc does not export this function, so we stub it out and detect
whether to build the stub code with autoconf.

This syscall has special semantics in x32 (no hi lo, just takes loff_t)
so we have to detect that case and use the appropriate arguments.

Signed-off-by: Boris Burkov <boris@bur.io>
---
 Makefile     |  4 ++--
 configure.ac |  1 +
 stubs.c      | 24 ++++++++++++++++++++++++
 stubs.h      | 11 +++++++++++
 4 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 stubs.c
 create mode 100644 stubs.h

diff --git a/Makefile b/Makefile
index c788b91b..11ecfc6c 100644
--- a/Makefile
+++ b/Makefile
@@ -173,12 +173,12 @@ libbtrfs_objects = common/send-stream.o common/send-utils.o kernel-lib/rbtree.o
 		   kernel-lib/raid56.o kernel-lib/tables.o \
 		   common/device-scan.o common/path-utils.o \
 		   common/utils.o libbtrfsutil/subvolume.o libbtrfsutil/stubs.o \
-		   crypto/hash.o crypto/xxhash.o $(CRYPTO_OBJECTS)
+		   crypto/hash.o crypto/xxhash.o $(CRYPTO_OBJECTS) stubs.o
 libbtrfs_headers = common/send-stream.h common/send-utils.h send.h kernel-lib/rbtree.h btrfs-list.h \
 	       crypto/crc32c.h kernel-lib/list.h kerncompat.h \
 	       kernel-lib/radix-tree.h kernel-lib/sizes.h kernel-lib/raid56.h \
 	       common/extent-cache.h kernel-shared/extent_io.h ioctl.h \
-	       kernel-shared/ctree.h btrfsck.h version.h
+	       kernel-shared/ctree.h btrfsck.h version.h stubs.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)
diff --git a/configure.ac b/configure.ac
index 7c2c9b8d..cbcfbe6d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -45,6 +45,7 @@ AC_CHECK_FUNCS([openat], [],
 	[AC_MSG_ERROR([cannot find openat() function])])
 
 AC_CHECK_FUNCS([reallocarray])
+AC_CHECK_FUNCS([pwritev2])
 
 m4_ifndef([PKG_PROG_PKG_CONFIG],
   [m4_fatal([Could not locate the pkg-config autoconf
diff --git a/stubs.c b/stubs.c
new file mode 100644
index 00000000..ab68a411
--- /dev/null
+++ b/stubs.c
@@ -0,0 +1,24 @@
+#if HAVE_PWRITEV2 != 1
+
+#include "stubs.h"
+
+#include "kerncompat.h"
+
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <sys/uio.h>
+
+ssize_t pwritev2(int fd, const struct iovec *iov, int iovcnt, off_t offset,
+		 int flags)
+{
+/* these conditions indicate an x32 system, which has a different pwritev2 */
+#if defined(__x86_64__) && defined(__ILP32__)
+	return syscall(SYS_pwritev2, fd, iov, iovcnt, offset, flags);
+#else
+	unsigned long hi = offset >> (BITS_PER_LONG / 2) >> (BITS_PER_LONG / 2);
+	unsigned long lo = offset;
+
+	return syscall(SYS_pwritev2, fd, iov, iovcnt, lo, hi, flags);
+#endif // X32
+}
+#endif /* HAVE_PWRIVEV2 */
diff --git a/stubs.h b/stubs.h
new file mode 100644
index 00000000..b39f8a69
--- /dev/null
+++ b/stubs.h
@@ -0,0 +1,11 @@
+#ifndef _BTRFS_STUBS_H
+#define _BTRFS_STUBS_H
+
+#include <sys/types.h>
+
+struct iovec;
+
+ssize_t pwritev2(int fd, const struct iovec *iov, int iovcnt, off_t offset,
+		 int flags);
+
+#endif
-- 
2.28.0


  parent reply	other threads:[~2020-08-21  7:41 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-21  7:39 [PATCH 0/9] btrfs: implement send/receive of compressed extents without decompressing Omar Sandoval
2020-08-21  7:39 ` [PATCH 1/9] btrfs: send: get rid of i_size logic in send_write() Omar Sandoval
2020-08-21 17:26   ` Filipe Manana
2020-08-24 17:39   ` Josef Bacik
2020-08-21  7:39 ` [PATCH 2/9] btrfs: send: avoid copying file data Omar Sandoval
2020-08-21 17:29   ` Filipe Manana
2020-08-24 21:34     ` Omar Sandoval
2020-08-24 17:47   ` Josef Bacik
2020-09-11 14:13   ` David Sterba
2020-09-14 22:04     ` Omar Sandoval
2020-09-15  8:14       ` David Sterba
2020-08-21  7:39 ` [PATCH 3/9] btrfs: send: use btrfs_file_extent_end() in send_write_or_clone() Omar Sandoval
2020-08-21 17:30   ` Filipe Manana
2020-08-21  7:39 ` [PATCH 4/9] btrfs: add send_stream_version attribute to sysfs Omar Sandoval
2020-08-21  7:39 ` [PATCH 5/9] btrfs: add send stream v2 definitions Omar Sandoval
2020-08-24 17:49   ` Josef Bacik
2020-08-21  7:39 ` [PATCH 6/9] btrfs: send: write larger chunks when using stream v2 Omar Sandoval
2020-08-24 17:57   ` Josef Bacik
2020-08-21  7:39 ` [PATCH 7/9] btrfs: send: allocate send buffer with alloc_page() and vmap() for v2 Omar Sandoval
2020-08-21  7:39 ` [PATCH 8/9] btrfs: send: send compressed extents with encoded writes Omar Sandoval
2020-08-24 17:32   ` Josef Bacik
2020-08-24 17:52     ` Omar Sandoval
2020-08-21  7:39 ` [PATCH 9/9] btrfs: send: enable support for stream v2 and compressed writes Omar Sandoval
2020-08-21  7:40 ` [PATCH 01/11] btrfs-progs: receive: support v2 send stream larger tlv_len Omar Sandoval
2020-08-21  7:40 ` [PATCH 02/11] btrfs-progs: receive: dynamically allocate sctx->read_buf Omar Sandoval
2020-08-21  7:40 ` [PATCH 03/11] btrfs-progs: receive: support v2 send stream DATA tlv format Omar Sandoval
2020-08-21  7:40 ` [PATCH 04/11] btrfs-progs: receive: add send stream v2 cmds and attrs to send.h Omar Sandoval
2020-08-21  7:40 ` Omar Sandoval [this message]
2020-08-21  7:40 ` [PATCH 06/11] btrfs-progs: receive: process encoded_write commands Omar Sandoval
2020-08-21  7:40 ` [PATCH 07/11] btrfs-progs: receive: encoded_write fallback to explicit decode and write Omar Sandoval
2020-08-21  7:40 ` [PATCH 08/11] btrfs-progs: receive: process fallocate commands Omar Sandoval
2020-08-21  7:40 ` [PATCH 09/11] btrfs-progs: receive: process setflags ioctl commands Omar Sandoval
2020-08-21  7:40 ` [PATCH 10/11] btrfs-progs: send: stream v2 ioctl flags Omar Sandoval
2020-08-21  7:40 ` [PATCH 11/11] btrfs-progs: receive: add tests for basic encoded_write send/receive Omar Sandoval
2020-08-24 19:57 ` [PATCH 0/9] btrfs: implement send/receive of compressed extents without decompressing David Sterba
2020-08-24 22:16   ` Omar Sandoval
2020-09-10 11:28 ` David Sterba

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