diff options
| author | teawater <zhuhui@kylinos.cn> | 2026-03-19 09:59:24 +0300 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-04-05 23:53:33 +0300 |
| commit | dc711106a0bc76a30e0fbd16ed4d348171547d9a (patch) | |
| tree | 76c6825e3f4b3d590148797c0dfd53567da3642c | |
| parent | 6ebf98d71f9b509e833e0af00795ad3723d2f410 (diff) | |
| download | linux-dc711106a0bc76a30e0fbd16ed4d348171547d9a.tar.xz | |
zsmalloc: return -EBUSY for zspage migration lock contention
movable_operations::migrate_page() should return an appropriate error code
for temporary migration failures so the migration core can handle them
correctly.
zs_page_migrate() currently returns -EINVAL when zspage_write_trylock()
fails. That path reflects transient lock contention, not invalid input,
so -EINVAL is clearly wrong.
However, -EAGAIN is also inappropriate here: the zspage's reader-lock
owner may hold the lock for an unbounded duration due to slow
decompression or reader-lock owner preemption. Since migration retries
are bounded by NR_MAX_MIGRATE_PAGES_RETRY and performed with virtually no
delay between attempts, there is no guarantee the lock will be released in
time for a retry to succeed. -EAGAIN implies "try again soon", which does
not hold in this case.
Return -EBUSY instead, which more accurately conveys that the resource is
occupied and migration cannot proceed at this time.
Link: https://lkml.kernel.org/r/20260319065924.69337-1-hui.zhu@linux.dev
Signed-off-by: teawater <zhuhui@kylinos.cn>
Acked-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | mm/zsmalloc.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 2c1430bf8d57..e7417ece1c12 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1727,7 +1727,19 @@ static int zs_page_migrate(struct page *newpage, struct page *page, if (!zspage_write_trylock(zspage)) { spin_unlock(&class->lock); write_unlock(&pool->lock); - return -EINVAL; + /* + * Return -EBUSY but not -EAGAIN: the zspage's reader-lock + * owner may hold the lock for an unbounded duration due to a + * slow decompression or reader-lock owner preemption. + * Since migration retries are bounded by + * NR_MAX_MIGRATE_PAGES_RETRY and performed with virtually no + * delay between attempts, there is no guarantee the lock will + * be released in time for a retry to succeed. + * -EAGAIN implies "try again soon", which does not hold here. + * -EBUSY more accurately conveys "resource is occupied, + * migration cannot proceed". + */ + return -EBUSY; } /* We're committed, tell the world that this is a Zsmalloc page. */ |