alistair23-linux

redonkable

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Darrick J. Wong f812e43e72 xfs: prohibit fs freezing when using empty transactions [ Upstream commit `27fb5a72f5` ] I noticed that fsfreeze can take a very long time to freeze an XFS if there happens to be a GETFSMAP caller running in the background. I also happened to notice the following in dmesg: ------------[ cut here ]------------ WARNING: CPU: 2 PID: 43492 at fs/xfs/xfs_super.c:853 xfs_quiesce_attr+0x83/0x90 [xfs] Modules linked in: xfs libcrc32c ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 ip_set_hash_ip ip_set_hash_net xt_tcpudp xt_set ip_set_hash_mac ip_set nfnetlink ip6table_filter ip6_tables bfq iptable_filter sch_fq_codel ip_tables x_tables nfsv4 af_packet [last unloaded: xfs] CPU: 2 PID: 43492 Comm: xfs_io Not tainted 5.6.0-rc4-djw #rc4 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.10.2-1ubuntu1 04/01/2014 RIP: 0010:xfs_quiesce_attr+0x83/0x90 [xfs] Code: 7c 07 00 00 85 c0 75 22 48 89 df 5b e9 96 c1 00 00 48 c7 c6 b0 2d 38 a0 48 89 df e8 57 64 ff ff 8b 83 7c 07 00 00 85 c0 74 de <0f> 0b 48 89 df 5b e9 72 c1 00 00 66 90 0f 1f 44 00 00 41 55 41 54 RSP: 0018:ffffc900030f3e28 EFLAGS: 00010202 RAX: 0000000000000001 RBX: ffff88802ac54000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff81e4a6f0 RDI: 00000000ffffffff RBP: ffff88807859f070 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000010 R12: 0000000000000000 R13: ffff88807859f388 R14: ffff88807859f4b8 R15: ffff88807859f5e8 FS: 00007fad1c6c0fc0(0000) GS:ffff88807e000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f0c7d237000 CR3: 0000000077f01003 CR4: 00000000001606a0 Call Trace: xfs_fs_freeze+0x25/0x40 [xfs] freeze_super+0xc8/0x180 do_vfs_ioctl+0x70b/0x750 ? __fget_files+0x135/0x210 ksys_ioctl+0x3a/0xb0 __x64_sys_ioctl+0x16/0x20 do_syscall_64+0x50/0x1a0 entry_SYSCALL_64_after_hwframe+0x49/0xbe These two things appear to be related. The assertion trips when another thread initiates a fsmap request (which uses an empty transaction) after the freezer waited for m_active_trans to hit zero but before the the freezer executes the WARN_ON just prior to calling xfs_log_quiesce. The lengthy delays in freezing happen because the freezer calls xfs_wait_buftarg to clean out the buffer lru list. Meanwhile, the GETFSMAP caller is continuing to grab and release buffers, which means that it can take a very long time for the buffer lru list to empty out. We fix both of these races by calling sb_start_write to obtain freeze protection while using empty transactions for GETFSMAP and for metadata scrubbing. The other two users occur during mount, during which time we cannot fs freeze. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>		2020-10-01 13:17:49 +02:00
Documentation	affs: fix basic permission bits to actually work	2020-09-09 19:12:34 +02:00
LICENSES	LICENSES: Rename other to deprecated	2019-05-03 06:34:32 -06:00
arch	KVM: LAPIC: Mark hrtimer for period or oneshot mode to expire in hard interrupt context	2020-10-01 13:17:45 +02:00
block	block: only call sched requeue_request() for scheduled requests	2020-09-23 12:40:37 +02:00
certs	PKCS#7: Refactor verify_pkcs7_signature()	2019-08-05 18:40:18 -04:00
crypto	crypto: af_alg - Work around empty control messages without MSG_MORE	2020-09-03 11:27:05 +02:00
drivers	brcmfmac: Fix double freeing in the fmac usb data path	2020-10-01 13:17:49 +02:00
fs	xfs: prohibit fs freezing when using empty transactions	2020-10-01 13:17:49 +02:00
include	exec: Add exec_update_mutex to replace cred_guard_mutex	2020-10-01 13:17:47 +02:00
init	exec: Add exec_update_mutex to replace cred_guard_mutex	2020-10-01 13:17:47 +02:00
ipc	ipc/util.c: sysvipc_find_ipc() incorrectly updates position index	2020-05-20 08:20:16 +02:00
kernel	perf: Use new infrastructure to fix deadlocks in execve	2020-10-01 13:17:48 +02:00
lib	kernel/sysctl-test: Add null pointer test for sysctl.c:proc_dointvec()	2020-10-01 13:17:10 +02:00
mm	mm: avoid data corruption on CoW fault into PFN-mapped VMA	2020-10-01 13:17:39 +02:00
net	Bluetooth: L2CAP: handle l2cap config request during open state	2020-10-01 13:17:41 +02:00
samples	bpf: Fix fds_example SIGSEGV error	2020-08-19 08:16:03 +02:00
scripts	checkpatch: fix the usage of capture group ( ... )	2020-09-09 19:12:37 +02:00
security	selinux: sel_avc_get_stat_idx should increase position index	2020-10-01 13:17:32 +02:00
sound	ASoC: SOF: ipc: check ipc return value before data copy	2020-10-01 13:17:37 +02:00
tools	selftests/ptrace: add test cases for dead-locks	2020-10-01 13:17:48 +02:00
usr	initramfs: restore default compression behavior	2020-04-08 09:08:38 +02:00
virt	KVM: fix overflow of zero page refcount with ksm running	2020-10-01 13:17:31 +02:00
.clang-format	clang-format: Update with the latest for_each macro list	2019-08-31 10:00:51 +02:00
.cocciconfig	…
.get_maintainer.ignore	Opt out of scripts/get_maintainer.pl	2019-05-16 10:53:40 -07:00
.gitattributes	.gitattributes: set git diff driver for C source code files	2016-10-07 18:46:30 -07:00
.gitignore	Modules updates for v5.4	2019-09-22 10:34:46 -07:00
.mailmap	ARM: SoC fixes	2019-11-10 13:41:59 -08:00
COPYING	COPYING: use the new text with points to the license files	2018-03-23 12:41:45 -06:00
CREDITS	MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer	2019-10-10 08:12:51 -07:00
Kbuild	kbuild: do not descend to ./Kbuild when cleaning	2019-08-21 21:03:58 +09:00
Kconfig	docs: kbuild: convert docs to ReST and rename to *.rst	2019-06-14 14:21:21 -06:00
MAINTAINERS	Documentation/llvm: add documentation on building w/ Clang/LLVM	2020-08-26 10:40:46 +02:00
Makefile	Linux 5.4.68	2020-09-26 18:03:16 +02:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.