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mm/damon/core: introduce damon_call_control->dealloc_on_cancel

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JIRA: https://redhat.atlassian.net/browse/RHEL-145695

commit e6a0deb6fa5b0fc134ee2aa127d1cfc9456d8445
Author: SeongJae Park <sj@kernel.org>
Date:   Mon Sep 8 13:15:12 2025 -0700

    mm/damon/core: introduce damon_call_control->dealloc_on_cancel

    Patch series "mm/damon/sysfs: fix refresh_ms control overwriting on
    multi-kdamonds usages".

    Automatic esssential DAMON/DAMOS status update feature of DAMON sysfs
    interface (refresh_ms) is broken [1] for multiple DAMON contexts
    (kdamonds) use case, since it uses a global single damon_call_control
    object for all created DAMON contexts.  The fields of the object,
    particularly the list field is over-written for the contexts and it makes
    unexpected results including user-space hangup and kernel crashes [2].
    Fix it by extending damon_call_control for the use case and updating the
    usage on DAMON sysfs interface to use per-context dynamically allocated
    damon_call_control object.

    This patch (of 2):

    When damon_call_control->repeat is set, damon_call() is executed
    asynchronously, and is eventually canceled when kdamond finishes.  If the
    damon_call_control object is dynamically allocated, finding the place to
    deallocate the object is difficult.  Introduce a new damon_call_control
    field, namely dealloc_on_cancel, to ask the kdamond deallocates those
    dynamically allocated objects when those are canceled.

    Link: https://lkml.kernel.org/r/20250908201513.60802-3-sj@kernel.org
    Link: https://lkml.kernel.org/r/20250908201513.60802-2-sj@kernel.org
    Fixes: d809a7c64ba8 ("mm/damon/sysfs: implement refresh_ms file internal work")
    Signed-off-by: SeongJae Park <sj@kernel.org>
    Cc: Yunjeong Mun <yunjeong.mun@sk.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Rafael Aquini <raquini@redhat.com>
This commit is contained in:
Rafael Aquini
2026-07-31 14:51:05 -04:00
parent fa3e26fdc1
commit 23566d8021
2 changed files with 8 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/linux/damon.h
+2
View File
@@ -636,6 +636,7 @@ struct damon_operations {
* @data: Data that will be passed to @fn.
* @repeat: Repeat invocations.
* @return_code: Return code from @fn invocation.
* @dealloc_on_cancel: De-allocate when canceled.
*
* Control damon_call(), which requests specific kdamond to invoke a given
* function. Refer to damon_call() for more details.
@@ -645,6 +646,7 @@ struct damon_call_control {
void *data;
bool repeat;
int return_code;
bool dealloc_on_cancel;
/* private: internal use only */
/* informs if the kdamond finished handling of the request */
struct completion completion;
mm/damon/core.c
+6 -2
View File
@@ -2491,10 +2491,14 @@ static void kdamond_call(struct damon_ctx *ctx, bool cancel)
mutex_lock(&ctx->call_controls_lock);
list_del(&control->list);
mutex_unlock(&ctx->call_controls_lock);
if (!control->repeat)
if (!control->repeat) {
complete(&control->completion);
else
} else if (control->canceled && control->dealloc_on_cancel) {
kfree(control);
continue;
} else {
list_add(&control->list, &repeat_controls);
}
}
control = list_first_entry_or_null(&repeat_controls,
struct damon_call_control, list);