63492b8ddd
This is a backport of a collection of 12 upstream patches.
The main one being the switch to use a rwsem instead.
The next important one being the switch of the rwsem to be a
per filesystem lock instead of global.
See the individual patches for details. They did not require
much work or wiggling to get them applied.
They all come from Linus' tree and are easily located. As such
I have not modified their individual headers with upstream
commit ids.
Verification:
- two scripts, the concept behind them supplied by Vefa Bicakci.
The first one causes a lot of concurrent contention in sysfs.
The second script highlights how well systemd is also contending.
Run Script1 followed by Script2
Without this change, Script2 has timeouts and fails.
Script1:
for i in `seq 20`; do
(while :; do find /sys/fs/cgroup/ -type f -readable -print0 \
2>/dev/null | xargs -0 -n 20 -r cat >&/dev/null ; done) &
done
for i in `seq 10`; do
(while :; do systemd-run --scope -q sleep 0.5 >/dev/null; done) &
done
Script2:
while true; do
date -Is
/usr/bin/time -f %e systemctl enable -q lighttpd.service ||
break
/usr/bin/time -f %e systemctl disable -q lighttpd.service ||
break
/usr/bin/time -f %e systemctl restart -q lighttpd.service ||
break
sleep 0.5 || break
done
- also soak testing to ensure that these patches don't introduce issues
Partial-Bug: 2016028
Signed-off-by: Jim Somerville <jim.somerville@windriver.com>
Change-Id: I6ad64cd7c90f756c6eb904065febfeb516e73009
48 lines
1.6 KiB
Diff
48 lines
1.6 KiB
Diff
From e3ffb2492087e6d9b85c18fbc24b3d73b7d14dfd Mon Sep 17 00:00:00 2001
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From: Ian Kent <raven@themaw.net>
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Date: Fri, 16 Jul 2021 17:28:40 +0800
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Subject: [PATCH] kernfs: dont call d_splice_alias() under kernfs node lock
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The call to d_splice_alias() in kernfs_iop_lookup() doesn't depend on
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any kernfs node so there's no reason to hold the kernfs node lock when
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calling it.
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Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
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Signed-off-by: Ian Kent <raven@themaw.net>
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Link: https://lore.kernel.org/r/162642772000.63632.10672683419693513226.stgit@web.messagingengine.com
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Signed-off-by: Jim Somerville <jim.somerville@windriver.com>
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---
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fs/kernfs/dir.c | 6 ++----
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1 file changed, 2 insertions(+), 4 deletions(-)
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diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
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index cdc57ab2e5ea..51b35d6f9739 100644
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--- a/fs/kernfs/dir.c
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+++ b/fs/kernfs/dir.c
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@@ -1108,7 +1108,6 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
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struct dentry *dentry,
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unsigned int flags)
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{
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- struct dentry *ret;
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struct kernfs_node *parent = dir->i_private;
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struct kernfs_node *kn;
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struct inode *inode = NULL;
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@@ -1128,11 +1127,10 @@ static struct dentry *kernfs_iop_lookup(struct inode *dir,
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/* Needed only for negative dentry validation */
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if (!inode)
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kernfs_set_rev(parent, dentry);
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- /* instantiate and hash (possibly negative) dentry */
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- ret = d_splice_alias(inode, dentry);
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up_read(&kernfs_rwsem);
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- return ret;
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+ /* instantiate and hash (possibly negative) dentry */
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+ return d_splice_alias(inode, dentry);
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}
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static int kernfs_iop_mkdir(struct inode *dir, struct dentry *dentry,
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--
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2.25.1
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