diff mbox series

[net,1/4] net/mlx5e: SHAMPO, Fix page leak

Message ID 20240815071611.2211873-2-tariqt@nvidia.com (mailing list archive)
State Accepted
Commit f232de7cdb4b99adb2c7f2bc5e0b7e4e1292873b
Delegated to: Netdev Maintainers
Headers show
Series mlx5 misc fixes 2024-08-15 | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 29 this patch: 29
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers warning 1 maintainers not CCed: linux-rdma@vger.kernel.org
netdev/build_clang success Errors and warnings before: 29 this patch: 29
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 29 this patch: 29
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 7 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-08-16--21-00 (tests: 710)

Commit Message

Tariq Toukan Aug. 15, 2024, 7:16 a.m. UTC 
From: Dragos Tatulea <dtatulea@nvidia.com>

When SHAMPO is used, a receive queue currently almost always leaks one
page on shutdown.

A page has MLX5E_SHAMPO_WQ_HEADER_PER_PAGE (8) headers. These headers
are tracked in the SHAMPO bitmap. Each page is released when the last
header index in the group is processed. During header allocation, there
can be leftovers from a page that will be used in a subsequent
allocation. This is normally fine, except for the following  scenario
(simplified a bit):

1) Allocate N new page fragments, showing only the relevant last 4
   fragments:

    0: new page
    1: new page
    2: new page
    3: new page
    4: page from previous allocation
    5: page from previous allocation
    6: page from previous allocation
    7: page from previous allocation

2) NAPI processes header indices 4-7 because they are the oldest
   allocated. Bit 7 will be set to 0.

3) Receive queue shutdown occurs. All the remaining bits are being
   iterated on to release the pages. But the page assigned to header
   indices 0-3 will not be freed due to what happened in step 2.

This patch fixes the issue by making sure that on allocation, header
fragments are always allocated in groups of
MLX5E_SHAMPO_WQ_HEADER_PER_PAGE so that there is never a partial page
left over between allocations.

A more appropriate fix would be a refactoring of
mlx5e_alloc_rx_hd_mpwqe() and mlx5e_build_shampo_hd_umr(). But this
refactoring is too big for net. It will be targeted for net-next.

Fixes: e839ac9a89cb ("net/mlx5e: SHAMPO, Simplify header page release in teardown")
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_rx.c | 1 +
 1 file changed, 1 insertion(+)
diff mbox series

Patch

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index 225da8d691fc..23aa555ca0ae 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -735,6 +735,7 @@  static int mlx5e_alloc_rx_hd_mpwqe(struct mlx5e_rq *rq)
 	ksm_entries = bitmap_find_window(shampo->bitmap,
 					 shampo->hd_per_wqe,
 					 shampo->hd_per_wq, shampo->pi);
+	ksm_entries = ALIGN_DOWN(ksm_entries, MLX5E_SHAMPO_WQ_HEADER_PER_PAGE);
 	if (!ksm_entries)
 		return 0;