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1b6b26ae70
linux/fs
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Linus Torvalds 1b6b26ae70 pipe: fix and clarify pipe write wakeup logic 
The pipe rework ends up having been extra painful, partly becaused of
actual bugs with ordering and caching of the pipe state, but also
because of subtle performance issues.

In particular, the pipe rework caused the kernel build to inexplicably
slow down.

The reason turns out to be that the GNU make jobserver (which limits the
parallelism of the build) uses a pipe to implement a "token" system: a
parallel submake will read a character from the pipe to get the job
token before starting a new job, and will write a character back to the
pipe when it is done.  The overall job limit is thus easily controlled
by just writing the appropriate number of initial token characters into
the pipe.

But to work well, that really means that the old behavior of write
wakeups being synchronous (WF_SYNC) is very important - when the pipe
writer wakes up a reader, we want the reader to actually get scheduled
immediately.  Otherwise you lose the parallelism of the build.

The pipe rework lost that synchronous wakeup on write, and we had
clearly all forgotten the reasons and rules for it.

This rewrites the pipe write wakeup logic to do the required Wsync
wakeups, but also clarifies the logic and avoids extraneous wakeups.

It also ends up addign a number of comments about what oit does and why,
so that we hopefully don't end up forgetting about this next time we
change this code.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-12-07 12:14:28 -08:00
..
9p 9p pull request for inclusion in 5.4 2019-09-27 15:10:34 -07:00
adfs Merge branch 'work.adfs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 11:33:22 -07:00
affs affs: fix a memory leak in affs_remount 2019-11-18 14:26:43 +01:00
afs AFS development 2019-11-30 10:57:22 -08:00
autofs Merge branch 'next.autofs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-12-05 17:11:48 -08:00
befs fs: Fill in max and min timestamps in superblock 2019-08-30 07:27:17 -07:00
bfs fs: Fill in max and min timestamps in superblock 2019-08-30 07:27:17 -07:00
btrfs compat_ioctl: remove most of fs/compat_ioctl.c 2019-12-01 13:46:15 -08:00
cachefiles treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
ceph The two highlights are a set of improvements to how rbd read-only 2019-12-05 13:06:51 -08:00
cifs Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-12-06 09:06:58 -08:00
coda y2038: add inode timestamp clamping 2019-09-19 09:42:37 -07:00
configfs configfs: calculate the depth of parent item 2019-11-06 18:36:01 +01:00
cramfs cramfs: fix usage on non-MTD device 2019-11-23 21:44:49 -05:00
crypto fscrypt: add support for IV_INO_LBLK_64 policies 2019-11-06 12:34:36 -08:00
debugfs Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-12-06 09:06:58 -08:00
devpts devpts_pty_kill(): don't bother with d_delete() 2019-09-03 09:30:56 -04:00
dlm dlm for 5.3 2019-07-12 17:37:53 -07:00
ecryptfs compat_ioctl: remove most of fs/compat_ioctl.c 2019-12-01 13:46:15 -08:00
efivarfs Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
efs fs: Fill in max and min timestamps in superblock 2019-08-30 07:27:17 -07:00
erofs erofs: remove unnecessary output in erofs_show_options() 2019-11-24 11:02:41 +08:00
exportfs exportfs_decode_fh(): negative pinned may become positive without the parent locked 2019-11-10 11:56:05 -05:00
ext2 \n 2019-11-30 11:16:07 -08:00
ext4 compat_ioctl: remove most of fs/compat_ioctl.c 2019-12-01 13:46:15 -08:00
f2fs compat_ioctl: remove most of fs/compat_ioctl.c 2019-12-01 13:46:15 -08:00
fat compat_ioctl: move drivers to compat_ptr_ioctl 2019-10-23 17:23:43 +02:00
freevxfs fs: Fill in max and min timestamps in superblock 2019-08-30 07:27:17 -07:00
fscache Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs" 2019-07-10 18:43:43 -07:00
fuse pipe: Fix iteration end check in fuse_dev_splice_write() 2019-12-06 13:57:04 -08:00
gfs2 GFS2 changes for this merge window: 2019-12-05 13:20:11 -08:00
hfs treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
hfsplus fs/hfsplus/xattr.c: replace strncpy with memcpy 2019-07-16 19:23:23 -07:00
hostfs This pull request contains the following changes for UML: 2019-05-12 17:52:13 -04:00
hpfs fs: compat_ioctl: move FITRIM emulation into file systems 2019-10-23 17:23:46 +02:00
hugetlbfs hugetlb: remove unused hstate in hugetlb_fault_mutex_hash() 2019-12-01 12:59:08 -08:00
iomap iomap: remove unneeded variable in iomap_dio_rw() 2019-11-26 09:28:47 -08:00
isofs y2038: add inode timestamp clamping 2019-09-19 09:42:37 -07:00
jbd2 This merge window saw the the following new featuers added to ext4: 2019-11-30 10:53:02 -08:00
jffs2 Revert "jffs2: Fix possible null-pointer dereferences in jffs2_add_frag_to_fragtree()" 2019-11-29 11:29:58 +01:00
jfs y2038: add inode timestamp clamping 2019-09-19 09:42:37 -07:00
kernfs Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-12-06 09:06:58 -08:00
lockd lockd: Make two symbols static 2019-07-03 17:52:09 -04:00
minix fs: Fill in max and min timestamps in superblock 2019-08-30 07:27:17 -07:00
nfs NFS: Fix an RCU lock leak in nfs4_refresh_delegation_stateid() 2019-11-01 11:03:56 -04:00
nfs_common treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
nfsd new helper: lookup_positive_unlocked() 2019-11-15 13:49:04 -05:00
nilfs2 fs: compat_ioctl: move FITRIM emulation into file systems 2019-10-23 17:23:46 +02:00
nls treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
notify compat_ioctl: remove most of fs/compat_ioctl.c 2019-12-01 13:46:15 -08:00
ntfs ntfs: remove (un)?likely() from IS_ERR() conditions 2019-09-26 10:10:44 -07:00
ocfs2 Merge branch 'akpm' (patches from Andrew) 2019-12-01 20:36:41 -08:00
omfs fs: omfs: Initialize filesystem timestamp ranges 2019-08-30 08:11:25 -07:00
openpromfs Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
orangefs Orangefs: a fix and a cleanup 2019-09-19 10:21:35 -07:00
overlayfs new helper: lookup_positive_unlocked() 2019-11-15 13:49:04 -05:00
proc fs/proc/Kconfig: fix indentation 2019-12-04 19:44:11 -08:00
pstore pstore: Make pstore_choose_compression() static 2019-10-29 09:43:03 -07:00
qnx4 fs: Fill in max and min timestamps in superblock 2019-08-30 07:27:17 -07:00
qnx6 fs: Fill in max and min timestamps in superblock 2019-08-30 07:27:17 -07:00
quota Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-12-06 09:06:58 -08:00
ramfs vfs: Convert ramfs, shmem, tmpfs, devtmpfs, rootfs to use the new mount API 2019-09-12 21:05:34 -04:00
reiserfs reiserfs: replace open-coded atomic_dec_and_mutex_lock() 2019-11-05 12:25:22 +01:00
romfs Merge branch 'work.mount2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-09-19 10:06:57 -07:00
squashfs Merge branch 'work.mount2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-09-19 10:06:57 -07:00
sysfs Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
sysv fs: sysv: Initialize filesystem timestamp ranges 2019-08-30 07:27:18 -07:00
tracefs tracing: Do not create tracefs files if tracefs lockdown is in effect 2019-10-12 20:49:07 -04:00
ubifs ubifs: ubifs_tnc_start_commit: Fix OOB in layout_in_gaps 2019-11-17 22:22:54 +01:00
udf fs-udf: Delete an unnecessary check before brelse() 2019-09-04 18:19:43 +02:00
ufs y2038: add inode timestamp clamping 2019-09-19 09:42:37 -07:00
unicode unicode: make array 'token' static const, makes object smaller 2019-09-17 11:48:24 -04:00
verity fs-verity: support builtin file signatures 2019-08-12 19:33:50 -07:00
xfs New code for 5.5: 2019-12-02 14:46:22 -08:00
aio.c y2038: syscall implementation cleanups 2019-12-01 14:00:59 -08:00
anon_inodes.c Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
attr.c timestamp_truncate: Replace users of timespec64_trunc 2019-08-30 07:27:17 -07:00
bad_inode.c get rid of 'opened' argument of ->atomic_open() - part 3 2018-07-12 10:04:20 -04:00
binfmt_aout.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
binfmt_elf_fdpic.c y2038: elfcore: Use __kernel_old_timeval for process times 2019-11-15 14:38:29 +01:00
binfmt_elf.c fs/binfmt_elf.c: extract elf_read() function 2019-12-04 19:44:13 -08:00
binfmt_em86.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
binfmt_flat.c fs/binfmt_flat.c: remove set but not used variable 'inode' 2019-07-16 19:23:22 -07:00
binfmt_misc.c Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
binfmt_script.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
block_dev.c block: don't send uevent for empty disk when not invalidating 2019-12-02 18:49:30 -07:00
buffer.c fs/buffer.c: include internal.h for missing declarations 2019-12-01 06:29:17 -08:00
char_dev.c chardev: set variable ret to -EBUSY before checking minor range overlap 2019-05-24 20:50:36 +02:00
compat_binfmt_elf.c y2038: elfcore: Use __kernel_old_timeval for process times 2019-11-15 14:38:29 +01:00
compat_ioctl.c New code for 5.5: 2019-12-02 14:46:22 -08:00
compat.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
coredump.c coredump: split pipe command whitespace before expanding template 2019-08-03 07:02:01 -07:00
d_path.c [PATCH] fix d_absolute_path() interplay with fsmount() 2019-08-30 19:31:09 -04:00
dax.c New code for 5.5: 2019-11-30 10:44:49 -08:00
dcache.c Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-12-06 09:06:58 -08:00
dcookies.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
direct-io.c fs/direct-io.c: keep dio_warn_stale_pagecache() when CONFIG_BLOCK=n 2019-12-01 06:29:18 -08:00
drop_caches.c fs/drop_caches.c: avoid softlockups in drop_pagecache_sb() 2019-02-01 15:46:24 -08:00
eventfd.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
eventpoll.c fs/epoll: remove unnecessary wakeups of nested epoll 2019-12-04 19:44:13 -08:00
exec.c Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-12-03 12:20:25 -08:00
fcntl.c fcntl: fix typo in RWH_WRITE_LIFE_NOT_SET r/w hint name 2019-10-25 14:28:10 -06:00
fhandle.c fs/handle.c - fix up kerneldoc 2019-08-07 21:51:47 -04:00
file_table.c vfs: Export flush_delayed_fput for use by knfsd. 2019-08-19 11:00:39 -04:00
file.c Revert "vfs: properly and reliably lock f_pos in fdget_pos()" 2019-11-26 11:34:06 -08:00
filesystems.c vfs: Implement a filesystem superblock creation/configuration context 2019-02-28 03:29:26 -05:00
fs_context.c vfs: subtype handling moved to fuse 2019-09-06 21:28:49 +02:00
fs_parser.c vfs: Make fs_parse() handle fs_param_is_fd-type params better 2019-09-12 21:06:14 -04:00
fs_pin.c switch the remnants of releasing the mountpoint away from fs_pin 2019-07-16 22:52:37 -04:00
fs_struct.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
fs_types.c fs: common implementation of file type 2019-01-21 17:48:13 +01:00
fs-writeback.c cgroup,writeback: don't switch wbs immediately on dead wbs if the memcg is dead 2019-11-08 13:37:24 -07:00
fsopen.c Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
inode.c mm,thp: avoid writes to file with THP in pagecache 2019-09-24 15:54:11 -07:00
internal.h Merge branch 'work.dcache2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-20 09:15:51 -07:00
io_uring.c io_uring: fix a typo in a comment 2019-12-05 07:59:37 -07:00
io-wq.c io_uring: use current task creds instead of allocating a new one 2019-12-02 08:50:00 -07:00
io-wq.h io-wq: clear node->next on list deletion 2019-12-04 17:26:57 -07:00
ioctl.c New code for 5.5: 2019-12-02 14:46:22 -08:00
Kconfig io-wq: small threadpool implementation for io_uring 2019-10-29 12:43:00 -06:00
Kconfig.binfmt binfmt_flat: make support for old format binaries optional 2019-06-24 09:16:47 +10:00
libfs.c fs/libfs.c: fix kernel-doc warning 2019-10-14 15:04:01 -07:00
locks.c Highlights: 2019-09-27 17:00:27 -07:00
Makefile io-wq: small threadpool implementation for io_uring 2019-10-29 12:43:00 -06:00
mbcache.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
mount.h switch the remnants of releasing the mountpoint away from fs_pin 2019-07-16 22:52:37 -04:00
mpage.c blkcg, writeback: Rename wbc_account_io() to wbc_account_cgroup_owner() 2019-07-10 09:00:57 -06:00
namei.c Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-12-06 09:06:58 -08:00
namespace.c fs/namespace.c: fix use-after-free of mount in mnt_warn_timestamp_expiry() 2019-10-16 23:15:09 -04:00
no-block.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
nsfs.c vfs: Convert nsfs to use the new mount API 2019-05-25 18:00:06 -04:00
open.c Revert "vfs: properly and reliably lock f_pos in fdget_pos()" 2019-11-26 11:34:06 -08:00
pipe.c pipe: fix and clarify pipe write wakeup logic 2019-12-07 12:14:28 -08:00
pnode.c fs/namespace: fix unprivileged mount propagation 2019-06-17 17:36:09 -04:00
pnode.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 209 2019-05-30 11:29:53 -07:00
posix_acl.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
proc_namespace.c vfs: subtype handling moved to fuse 2019-09-06 21:28:49 +02:00
read_write.c vfs: fix page locking deadlocks when deduping files 2019-08-16 18:43:24 -07:00
readdir.c filldir[64]: remove WARN_ON_ONCE() for bad directory entries 2019-10-18 18:41:16 -04:00
select.c y2038: syscalls: change remaining timeval to __kernel_old_timeval 2019-11-15 14:38:29 +01:00
seq_file.c seq_file: fix problem when seeking mid-record 2019-08-13 16:06:52 -07:00
signalfd.c fs: mark expected switch fall-throughs 2019-04-08 18:21:02 -05:00
splice.c pipe: fix incorrect caching of pipe state over pipe_wait() 2019-12-06 12:40:35 -08:00
stack.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
stat.c fs: move generic stat response attr handling to vfs_getattr_nosec 2019-02-01 01:55:45 -05:00
statfs.c vfs: Fix EOVERFLOW testing in put_compat_statfs64 2019-10-03 14:21:35 -07:00
super.c Merge branch 'work.mount3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-10-10 08:16:44 -07:00
sync.c fs/sync.c: sync_file_range(2) may use WB_SYNC_ALL writeback 2019-05-14 09:47:50 -07:00
timerfd.c y2038: timerfd: Use timespec64 internally 2019-11-15 14:38:30 +01:00
userfaultfd.c Merge branch 'akpm' (patches from Andrew) 2019-12-01 20:36:41 -08:00
utimes.c y2038: syscalls: change remaining timeval to __kernel_old_timeval 2019-11-15 14:38:29 +01:00
xattr.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00