!25 [sync] PR-21: fix exclusive op enqueue timeout

From: @openeuler-sync-bot 
Reviewed-by: @swf504 
Signed-off-by: @swf504

0001-fix-exclusive-op-enqueue-timeout.patch

@@ -0,0 +1,86 @@
+From d03594b0313db71413b9dcb040f8d5c4da7213b1 Mon Sep 17 00:00:00 2001
+From: David Sterba <dsterba@suse.com>
+Date: Thu, 18 Apr 2024 18:24:48 +0800
+Subject: [PATCH] fix exclusive op enqueue timeout
+There's a report that 'btrfs balance start --enqueue' does not properly
+wait when there are multiple instances started. The command does a busy
+wait instead of timeouts.
+
+Strace output:
+
+     0.000006 pselect6(5, NULL, NULL, [4], {tv_sec=60, tv_nsec=0}, NULL) = 1 (except [4], left {tv_sec=59, tv_nsec=999999716})
+     0.000008 pselect6(5, NULL, NULL, [4], {tv_sec=29, tv_nsec=999999000}, NULL) = 1 (except [4], left {tv_sec=29, tv_nsec=999998786})
+
+After the first select there's almost the entire time left, the second
+one starts right after it.
+
+Polling/selecting sysfs files is possible under some conditions:
+
+- the file descriptor must be reopened before each poll/select
+- the whole buffer must be read too
+
+With that in place it now works as expected. The remaining timeout logic
+is slightly adjusted to wait at most 10 seconds so the pending jobs do
+not wait too long if there's still a lot of time left from the first
+select.
+
+Issue: #746
+Signed-off-by: David Sterba <dsterba@suse.com>
+---
+ common/utils.c | 21 ++++++++++++++++++++-
+ 1 file changed, 20 insertions(+), 1 deletion(-)
+
+diff --git a/common/utils.c b/common/utils.c
+index 62f0e3f..7cde492 100644
+--- a/common/utils.c
++++ b/common/utils.c
+@@ -1326,26 +1326,45 @@ int check_running_fs_exclop(int fd, enum exclusive_operation start, bool enqueue
+ 		fflush(stdout);
+ 	}
+ 
++	/*
++	 * The sysfs file descriptor needs to be reopened and all data read
++	 * before each select().
++	 */
+ 	while (exclop > 0) {
+ 		fd_set fds;
+ 		struct timeval tv = { .tv_sec = 60, .tv_usec = 0 };
++		char tmp[1024];
+ 
++		close(sysfs_fd);
++		sysfs_fd = sysfs_open_fsid_file(fd, "exclusive_operation");
++		if (sysfs_fd < 0)
++			return sysfs_fd;
+ 		FD_ZERO(&fds);
+ 		FD_SET(sysfs_fd, &fds);
+ 
++		ret = read(sysfs_fd, tmp, sizeof(tmp));
+ 		ret = select(sysfs_fd + 1, NULL, NULL, &fds, &tv);
+ 		if (ret < 0) {
+ 			ret = -errno;
+ 			break;
+ 		}
+ 		if (ret > 0) {
++			close(sysfs_fd);
++			sysfs_fd = sysfs_open_fsid_file(fd, "exclusive_operation");
++			if (sysfs_fd < 0)
++				return sysfs_fd;
++
++			FD_ZERO(&fds);
++			FD_SET(sysfs_fd, &fds);
++
++			ret = read(sysfs_fd, tmp, sizeof(tmp));
+ 			/*
+ 			 * Notified before the timeout, check again before
+ 			 * returning. In case there are more operations
+ 			 * waiting, we want to reduce the chances to race so
+ 			 * reuse the remaining time to randomize the order.
+ 			 */
+-			tv.tv_sec /= 2;
++			tv.tv_sec = (tv.tv_sec % 10) + 1;
+ 			ret = select(sysfs_fd + 1, NULL, NULL, &fds, &tv);
+ 			exclop = get_fs_exclop(fd);
+ 			if (exclop <= 0)
+-- 
+2.43.0
+

btrfs-progs.spec

@@ -1,11 +1,13 @@
 Name:       btrfs-progs
 Version:    6.6.3
-Release:    1
+Release:    2
 Summary:    btrfs userspace programs
 License:    GPLv2 and GPL+ and LGPL-2.1+ and GPL-3.0+ and LGPL-2.1 and MIT
 URL:        https://btrfs.wiki.kernel.org/index.php/Main_Page
 Source0:    https://www.kernel.org/pub/linux/kernel/people/kdave/%{name}/%{name}-v%{version}.tar.xz
 
+Patch0001:  0001-fix-exclusive-op-enqueue-timeout.patch
+
 BuildRequires:  python3-devel >= 3.4
 BuildRequires:  libacl-devel, e2fsprogs-devel, libblkid-devel, libuuid-devel, zlib-devel, libzstd-devel, lzo-devel, systemd-devel
 BuildRequires:  gcc, asciidoc, systemd, xmlto, autoconf, automake, python3-sphinx
@@ -70,6 +72,9 @@ make mandir=%{_mandir} bindir=%{_sbindir} libdir=%{_libdir} incdir=%{_includedir
 %{_mandir}/man8/*.gz
 
 %changelog
+* Fri Apr 19 2024 cenhuilin <cenhuilin@kylinos.cn> - 6.6.3-2
+- fix exclusive op enqueue timeout
+
 * Wed Jan 17 2024 wuguanghao <wuguanghao3@huawei.com> - 6.6.3-1
 - upgrade version to 6.6.3