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| author | Vineet Agarwal <agarwal.vineet2006@gmail.com> | 2026-04-29 19:34:34 +0530 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-05-28 21:05:03 -0700 |
| commit | ab3fad1b1cdc7aab95c49f389642c4fb88a4f35e (patch) | |
| tree | 4cedb98937a0be40db6133e2adb03c1066be63a3 /mm | |
| parent | 9f7ff45e99d322077af7f53f4a0a2b0907816531 (diff) | |
| download | linux-next-history-ab3fad1b1cdc7aab95c49f389642c4fb88a4f35e.tar.gz | |
mm/khugepaged: return -EAGAIN for SCAN_PAGE_HAS_PRIVATE in MADV_COLLAPSE
MADV_COLLAPSE uses errno values to provide actionable feedback to
userspace. Temporary resource constraints are mapped to -EAGAIN so the
caller may retry, while intrinsic failures of the specified range are
mapped to -EINVAL.
collapse_file() returns SCAN_PAGE_HAS_PRIVATE when filemap_release_folio()
fails while isolating file-backed folios for collapse. This currently
falls through the default case in madvise_collapse_errno() and is reported
to userspace as -EINVAL.
However, filemap_release_folio() failure commonly reflects temporary folio
state rather than a permanently uncollapsible range.
For example, ext4 returns false when a folio still has dirty journalled
data, btrfs returns false for dirty or writeback folios before extent
state release, and NFS may return false while reclaiming
filesystem-private folio state.
In such cases, retrying MADV_COLLAPSE after writeback, reclaim or journal
progress may succeed. This matches the existing -EAGAIN handling for
SCAN_PAGE_DIRTY_OR_WRITEBACK and other transient collapse failures more
closely than -EINVAL.
Therefore, map SCAN_PAGE_HAS_PRIVATE to -EAGAIN so userspace receives
retryable feedback for this temporary failure path.
Link: https://lore.kernel.org/20260429140434.439456-1-agarwal.vineet2006@gmail.com
Signed-off-by: Vineet Agarwal <agarwal.vineet2006@gmail.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/khugepaged.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 5f4e009593e01..28a843f30b32b 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2808,6 +2808,7 @@ static int madvise_collapse_errno(enum scan_result r) case SCAN_PAGE_LRU: case SCAN_DEL_PAGE_LRU: case SCAN_PAGE_FILLED: + case SCAN_PAGE_HAS_PRIVATE: case SCAN_PAGE_DIRTY_OR_WRITEBACK: return -EAGAIN; /* |