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 --- fs/squashfs/decompressor.c | 141 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 141 insertions(+) create mode 100644 fs/squashfs/decompressor.c (limited to 'fs/squashfs/decompressor.c') diff --git a/fs/squashfs/decompressor.c b/fs/squashfs/decompressor.c new file mode 100644 index 000000000..a676084be --- /dev/null +++ b/fs/squashfs/decompressor.c @@ -0,0 +1,141 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Squashfs - a compressed read only filesystem for Linux + * + * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 + * Phillip Lougher + * + * decompressor.c + */ + +#include +#include +#include + +#include "squashfs_fs.h" +#include "squashfs_fs_sb.h" +#include "decompressor.h" +#include "squashfs.h" +#include "page_actor.h" + +/* + * This file (and decompressor.h) implements a decompressor framework for + * Squashfs, allowing multiple decompressors to be easily supported + */ + +static const struct squashfs_decompressor squashfs_lzma_unsupported_comp_ops = { + NULL, NULL, NULL, NULL, LZMA_COMPRESSION, "lzma", 0 +}; + +#ifndef CONFIG_SQUASHFS_LZ4 +static const struct squashfs_decompressor squashfs_lz4_comp_ops = { + NULL, NULL, NULL, NULL, LZ4_COMPRESSION, "lz4", 0 +}; +#endif + +#ifndef CONFIG_SQUASHFS_LZO +static const struct squashfs_decompressor squashfs_lzo_comp_ops = { + NULL, NULL, NULL, NULL, LZO_COMPRESSION, "lzo", 0 +}; +#endif + +#ifndef CONFIG_SQUASHFS_XZ +static const struct squashfs_decompressor squashfs_xz_comp_ops = { + NULL, NULL, NULL, NULL, XZ_COMPRESSION, "xz", 0 +}; +#endif + +#ifndef CONFIG_SQUASHFS_ZLIB +static const struct squashfs_decompressor squashfs_zlib_comp_ops = { + NULL, NULL, NULL, NULL, ZLIB_COMPRESSION, "zlib", 0 +}; +#endif + +#ifndef CONFIG_SQUASHFS_ZSTD +static const struct squashfs_decompressor squashfs_zstd_comp_ops = { + NULL, NULL, NULL, NULL, ZSTD_COMPRESSION, "zstd", 0 +}; +#endif + +static const struct squashfs_decompressor squashfs_unknown_comp_ops = { + NULL, NULL, NULL, NULL, 0, "unknown", 0 +}; + +static const struct squashfs_decompressor *decompressor[] = { + &squashfs_zlib_comp_ops, + &squashfs_lz4_comp_ops, + &squashfs_lzo_comp_ops, + &squashfs_xz_comp_ops, + &squashfs_lzma_unsupported_comp_ops, + &squashfs_zstd_comp_ops, + &squashfs_unknown_comp_ops +}; + + +const struct squashfs_decompressor *squashfs_lookup_decompressor(int id) +{ + int i; + + for (i = 0; decompressor[i]->id; i++) + if (id == decompressor[i]->id) + break; + + return decompressor[i]; +} + + +static void *get_comp_opts(struct super_block *sb, unsigned short flags) +{ + struct squashfs_sb_info *msblk = sb->s_fs_info; + void *buffer = NULL, *comp_opts; + struct squashfs_page_actor *actor = NULL; + int length = 0; + + /* + * Read decompressor specific options from file system if present + */ + if (SQUASHFS_COMP_OPTS(flags)) { + buffer = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (buffer == NULL) { + comp_opts = ERR_PTR(-ENOMEM); + goto out; + } + + actor = squashfs_page_actor_init(&buffer, 1, 0); + if (actor == NULL) { + comp_opts = ERR_PTR(-ENOMEM); + goto out; + } + + length = squashfs_read_data(sb, + sizeof(struct squashfs_super_block), 0, NULL, actor); + + if (length < 0) { + comp_opts = ERR_PTR(length); + goto out; + } + } + + comp_opts = squashfs_comp_opts(msblk, buffer, length); + +out: + kfree(actor); + kfree(buffer); + return comp_opts; +} + + +void *squashfs_decompressor_setup(struct super_block *sb, unsigned short flags) +{ + struct squashfs_sb_info *msblk = sb->s_fs_info; + void *stream, *comp_opts = get_comp_opts(sb, flags); + + if (IS_ERR(comp_opts)) + return comp_opts; + + stream = msblk->thread_ops->create(msblk, comp_opts); + if (IS_ERR(stream)) + kfree(comp_opts); + + return stream; +} -- cgit v1.3.1