[PATCH v2 2/3] drm/ttm: Avoid invoking the OOM killer when reading back swapped content

Thomas Hellström
2026-03-17T14:19:30Z

In situations where the system is very short on RAM, the shmem
readback from swap-space may invoke the OOM killer.

However, since this might be a recoverable situation where the caller
is indicating this by setting
struct ttm_operation_ctx::gfp_retry_mayfail to true, adjust the gfp
value used by the allocation accordingly.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Maarten Lankhorst <dev@lankhorst.se>
---
drivers/gpu/drm/ttm/ttm_backup.c | 6 ++++--
drivers/gpu/drm/ttm/ttm_pool.c | 5 ++++-
include/drm/ttm/ttm_backup.h | 2 +-
3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_backup.c b/drivers/gpu/drm/ttm/ttm_backup.c
index 6bd4c123d94c..81df4cb5606b 100644
--- a/drivers/gpu/drm/ttm/ttm_backup.c
+++ b/drivers/gpu/drm/ttm/ttm_backup.c
@@ -44,18 +44,20 @@ void ttm_backup_drop(struct file *backup, pgoff_t handle)
* @dst: The struct page to copy into.
* @handle: The handle returned when the page was backed up.
* @intr: Try to perform waits interruptible or at least killable.
+ * @additional_gfp: GFP mask to add to the default GFP mask if any.
*
* Return: 0 on success, Negative error code on failure, notably
* -EINTR if @intr was set to true and a signal is pending.
*/
int ttm_backup_copy_page(struct file *backup, struct page *dst,
- pgoff_t handle, bool intr)
+ pgoff_t handle, bool intr, gfp_t additional_gfp)
{
struct address_space *mapping = backup->f_mapping;
struct folio *from_folio;
pgoff_t idx = ttm_backup_handle_to_shmem_idx(handle);

- from_folio = shmem_read_folio(mapping, idx);
+ from_folio = shmem_read_folio_gfp(mapping, idx, mapping_gfp_mask(mapping)
+ | additional_gfp);
if (IS_ERR(from_folio))
return PTR_ERR(from_folio);

diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
index 8fa9e09f6ee5..aa41099c5ecf 100644
--- a/drivers/gpu/drm/ttm/ttm_pool.c
+++ b/drivers/gpu/drm/ttm/ttm_pool.c
@@ -530,6 +530,8 @@ static int ttm_pool_restore_commit(struct ttm_pool_tt_restore *restore,
p = first_page[i];
if (ttm_backup_page_ptr_is_handle(p)) {
unsigned long handle = ttm_backup_page_ptr_to_handle(p);
+ gfp_t additional_gfp = ctx->gfp_retry_mayfail ?
+ __GFP_RETRY_MAYFAIL | __GFP_NOWARN : 0;

if (IS_ENABLED(CONFIG_FAULT_INJECTION) && ctx->interruptible &&
should_fail(&backup_fault_inject, 1)) {
@@ -543,7 +545,8 @@ static int ttm_pool_restore_commit(struct ttm_pool_tt_restore *restore,
}

ret = ttm_backup_copy_page(backup, restore->alloced_page + i,
- handle, ctx->interruptible);
+ handle, ctx->interruptible,
+ additional_gfp);
if (ret)
break;

diff --git a/include/drm/ttm/ttm_backup.h b/include/drm/ttm/ttm_backup.h
index c33cba111171..29b9c855af77 100644
--- a/include/drm/ttm/ttm_backup.h
+++ b/include/drm/ttm/ttm_backup.h
@@ -56,7 +56,7 @@ ttm_backup_page_ptr_to_handle(const struct page *page)
void ttm_backup_drop(struct file *backup, pgoff_t handle);

int ttm_backup_copy_page(struct file *backup, struct page *dst,
- pgoff_t handle, bool intr);
+ pgoff_t handle, bool intr, gfp_t additional_gfp);

s64
ttm_backup_backup_page(struct file *backup, struct page *page,
--
2.53.0