From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- Documentation/filesystems/ecryptfs.rst | 86 ++++++++++++++++++++++++++++++++++ 1 file changed, 86 insertions(+) create mode 100644 Documentation/filesystems/ecryptfs.rst (limited to 'Documentation/filesystems/ecryptfs.rst') diff --git a/Documentation/filesystems/ecryptfs.rst b/Documentation/filesystems/ecryptfs.rst new file mode 100644 index 000000000..1f2edef4c --- /dev/null +++ b/Documentation/filesystems/ecryptfs.rst @@ -0,0 +1,86 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====================================================== +eCryptfs: A stacked cryptographic filesystem for Linux +====================================================== + +eCryptfs is free software. Please see the file COPYING for details. +For documentation, please see the files in the doc/ subdirectory. For +building and installation instructions please see the INSTALL file. + +:Maintainer: Phillip Hellewell +:Lead developer: Michael A. Halcrow +:Developers: Michael C. Thompson + Kent Yoder +:Web Site: http://ecryptfs.sf.net + +This software is currently undergoing development. Make sure to +maintain a backup copy of any data you write into eCryptfs. + +eCryptfs requires the userspace tools downloadable from the +SourceForge site: + +http://sourceforge.net/projects/ecryptfs/ + +Userspace requirements include: + +- David Howells' userspace keyring headers and libraries (version + 1.0 or higher), obtainable from + http://people.redhat.com/~dhowells/keyutils/ +- Libgcrypt + + +.. note:: + + In the beta/experimental releases of eCryptfs, when you upgrade + eCryptfs, you should copy the files to an unencrypted location and + then copy the files back into the new eCryptfs mount to migrate the + files. + + +Mount-wide Passphrase +===================== + +Create a new directory into which eCryptfs will write its encrypted +files (i.e., /root/crypt). Then, create the mount point directory +(i.e., /mnt/crypt). Now it's time to mount eCryptfs:: + + mount -t ecryptfs /root/crypt /mnt/crypt + +You should be prompted for a passphrase and a salt (the salt may be +blank). + +Try writing a new file:: + + echo "Hello, World" > /mnt/crypt/hello.txt + +The operation will complete. Notice that there is a new file in +/root/crypt that is at least 12288 bytes in size (depending on your +host page size). This is the encrypted underlying file for what you +just wrote. To test reading, from start to finish, you need to clear +the user session keyring: + +keyctl clear @u + +Then umount /mnt/crypt and mount again per the instructions given +above. + +:: + + cat /mnt/crypt/hello.txt + + +Notes +===== + +eCryptfs version 0.1 should only be mounted on (1) empty directories +or (2) directories containing files only created by eCryptfs. If you +mount a directory that has pre-existing files not created by eCryptfs, +then behavior is undefined. Do not run eCryptfs in higher verbosity +levels unless you are doing so for the sole purpose of debugging or +development, since secret values will be written out to the system log +in that case. + + +Mike Halcrow +mhalcrow@us.ibm.com -- cgit v1.3.1