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SeongJae Park 7c303fa1f3 mm/damon/ops-common: ignore migration request to invalid nodes 
commit 7e6c313069 upstream.

damon_migrate_pages() tries migration even if the target node is invalid.
If users mistakenly make such invalid requests via
DAMOS_MIGRATE_{HOT,COLD} action, the below kernel BUG can happen.

    [ 7831.883495] BUG: unable to handle page fault for address: 0000000000001f48
    [ 7831.884160] #PF: supervisor read access in kernel mode
    [ 7831.884681] #PF: error_code(0x0000) - not-present page
    [ 7831.885203] PGD 0 P4D 0
    [ 7831.885468] Oops: Oops: 0000 [#1] SMP PTI
    [ 7831.885852] CPU: 31 UID: 0 PID: 94202 Comm: kdamond.0 Not tainted 6.16.0-rc5-mm-new-damon+ #93 PREEMPT(voluntary)
    [ 7831.886913] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-4.el9 04/01/2014
    [ 7831.887777] RIP: 0010:__alloc_frozen_pages_noprof (include/linux/mmzone.h:1724 include/linux/mmzone.h:1750 mm/page_alloc.c:4936 mm/page_alloc.c:5137)
    [...]
    [ 7831.895953] Call Trace:
    [ 7831.896195]  <TASK>
    [ 7831.896397] __folio_alloc_noprof (mm/page_alloc.c:5183 mm/page_alloc.c:5192)
    [ 7831.896787] migrate_pages_batch (mm/migrate.c:1189 mm/migrate.c:1851)
    [ 7831.897228] ? __pfx_alloc_migration_target (mm/migrate.c:2137)
    [ 7831.897735] migrate_pages (mm/migrate.c:2078)
    [ 7831.898141] ? __pfx_alloc_migration_target (mm/migrate.c:2137)
    [ 7831.898664] damon_migrate_folio_list (mm/damon/ops-common.c:321 mm/damon/ops-common.c:354)
    [ 7831.899140] damon_migrate_pages (mm/damon/ops-common.c:405)
    [...]

Add a target node validity check in damon_migrate_pages().  The validity
check is stolen from that of do_pages_move(), which is being used for the
move_pages() system call.

Link: https://lkml.kernel.org/r/20250720185822.1451-1-sj@kernel.org
Fixes: b51820ebea ("mm/damon/paddr: introduce DAMOS_MIGRATE_COLD action for demotion")	[6.11.x]
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Honggyu Kim <honggyu.kim@sk.com>
Cc: Hyeongtak Ji <hyeongtak.ji@sk.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-08-28 16:31:03 +02:00
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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 reStructuredText 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.