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Follow the object_action() naming convention for netmem non-page_pool
reference helpers by renaming get_netmem() and put_netmem() to
netmem_inc_ref() and netmem_dec_ref().
Use netmem_inc_ref() and netmem_dec_ref() rather than netmem_ref() and
netmem_unref() because netmem_ref is already a typedef (typedef unsigned
long __bitwise netmem_ref).
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mina Almasry <almasrymina@google.com>
Link: https://patch.msgid.link/20261021015558.4124825-3-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Previously, __skb_frag_ref() and skb_frag_ref() unconditionally
incremented the non-pp backing refcount via get_netmem(), while
skb_frag_unref() decremented pp_ref_count whenever skb->pp_recycle was
set. Ref-ing a page_pool fragment into a pp_recycle=1 SKB (or clearing
pp_recycle=0 on an uncloned SKB while clones still held pp_recycle=1)
leaked the backing non-pp refcount and underflowed pp_ref_count across
IP-TFS, skb_split(), skb_shift(), and cloned unclone paths.
Replace __skb_frag_ref() with skb_netmem_ref(netmem, recycle) as the
exact counterpart to skb_netmem_unref(netmem, recycle):
- Keep skb->pp_recycle intact in skb_release_data() so uncloning paths
(pskb_expand_head() and pskb_carve_inside_{header,nonlinear}()) keep
trading pp_ref_count references symmetrically across clones.
- Propagate pp_recycle and call skb_frag_ref() on the destination SKB in
__pskb_copy_fclone(), skb_zerocopy(), skb_split(), skb_shift(), and
skb_segment().
- Linearize an output segment's existing frags in skb_segment() before
attaching frags from a frag_list SKB with a different pp_recycle bit,
since each output segment carries a single pp_recycle bit.
- Use skb_frag_ref() in xfrm_iptfs, chcr_ktls, and cassini, and call
get_netmem() directly in veth and tls_device_fallback where callers
explicitly take a raw non-pp reference.
Found by code inspection while reviewing the IP-TFS pp_ref_count fix [1]
and confirmed with the KUnit tests added later in this series; not
observed in production. The xfrm_iptfs, chcr_ktls, cassini, veth, and
tls_device_fallback changes are compile-tested only.
Link: https://lore.kernel.org/netdev/xfrm-iptfs-pp_ref_count-underflow-v4-1-912fa72106f0@secunet.com/ [1]
Cc: Antony Antony <antony.antony@secunet.com>
Cc: Stanislav Fomichev <sdf@fomichev.me>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jesper Dangaard Brouer <hawk@kernel.org>
Cc: bpf@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Mina Almasry <almasrymina@google.com>
Tested-by: Antony Antony <antony.antony@secunet.com>
Link: https://patch.msgid.link/20261014173945.373295-5-almasrymina@google.com
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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skb_netmem_unref()
Unreferencing a page_pool fragment with recycle=false decrements the
non-pp backing refcount instead of pp_ref_count, underflowing the page
refcount when the fragment was owned via page_pool (as on mlx4's RX
error path). Having both skb_page_unref() and __skb_frag_unref(frag,
recycle) made it easy for callers to pass hardcoded recycle=false on
SKB-owned fragments.
Replace skb_page_unref() and __skb_frag_unref() with
skb_netmem_unref(netmem, recycle), which dispatches to
napi_pp_put_page() when recycle is true and put_netmem() otherwise:
- Use skb_frag_unref(skb, ...) on SKB-owned fragments in mlx4, sky2,
tls_strp, and skb_shift() so unrefs always match skb->pp_recycle.
- Use put_netmem() directly in tls_device's destroy_record(), which
releases raw non-pp page references outside an SKB.
Found by code inspection and confirmed with the KUnit tests added later
in this series; not observed in production. The mlx4, sky2, and TLS
call-site changes are compile-tested only.
Assisted-by: LLM
Signed-off-by: Mina Almasry <almasrymina@google.com>
Link: https://patch.msgid.link/20261014173945.373295-4-almasrymina@google.com
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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While napi_pp_put_page() releases a page_pool pp_ref_count reference on
a netmem, no symmetric helper existed to acquire one, forcing callers
like tcp_recvmsg_dmabuf() to open-code atomic_long_inc() on
niov->desc.pp_ref_count.
Add napi_pp_get_page() to pair symmetrically with napi_pp_put_page(),
and use WARN_ON_ONCE(!napi_pp_get_page(netmem)) in tcp_recvmsg_dmabuf()
to match WARN_ON_ONCE(!napi_pp_put_page(netmem)) in
tcp_release_user_frags().
Assisted-by: LLM
Signed-off-by: Mina Almasry <almasrymina@google.com>
Link: https://patch.msgid.link/20261014173945.373295-3-almasrymina@google.com
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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clang is not inlining skb_frag_unref() and __skb_frag_unref()
in gro fast path.
It also does not inline gro_try_pull_from_frag0().
Using __always_inline fixes this issue, makes the
kernel faster _and_ smaller.
Also change __skb_frag_ref(), skb_frag_ref() and skb_page_unref()
to let them inlined for the last patch in this series.
$ scripts/bloat-o-meter -t vmlinux.0 vmlinux.1
add/remove: 2/6 grow/shrink: 1/2 up/down: 218/-511 (-293)
Function old new delta
gro_pull_from_frag0 - 188 +188
__pfx_gro_pull_from_frag0 - 16 +16
skb_shift 1125 1139 +14
__pfx_skb_frag_unref 16 - -16
__pfx_gro_try_pull_from_frag0 16 - -16
__pfx___skb_frag_unref 16 - -16
__skb_frag_unref 36 - -36
skb_frag_unref 59 - -59
dev_gro_receive 1608 1514 -94
napi_gro_frags 892 771 -121
gro_try_pull_from_frag0 153 - -153
Total: Before=22566192, After=22565899, chg -0.00%
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260122045720.1221017-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Currently net_iovs support only pp ref counts, and do not support a
page ref equivalent.
This is fine for the RX path as net_iovs are used exclusively with the
pp and only pp refcounting is needed there. The TX path however does not
use pp ref counts, thus, support for get_page/put_page equivalent is
needed for netmem.
Support get_netmem/put_netmem. Check the type of the netmem before
passing it to page or net_iov specific code to obtain a page ref
equivalent.
For dmabuf net_iovs, we obtain a ref on the underlying binding. This
ensures the entire binding doesn't disappear until all the net_iovs have
been put_netmem'ed. We do not need to track the refcount of individual
dmabuf net_iovs as we don't allocate/free them from a pool similar to
what the buddy allocator does for pages.
This code is written to be extensible by other net_iov implementers.
get_netmem/put_netmem will check the type of the netmem and route it to
the correct helper:
pages -> [get|put]_page()
dmabuf net_iovs -> net_devmem_[get|put]_net_iov()
new net_iovs -> new helpers
Signed-off-by: Mina Almasry <almasrymina@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250508004830.4100853-3-almasrymina@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Make skb_frag_page() fail in the case where the frag is not backed
by a page, and fix its relevant callers to handle this case.
Signed-off-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20240910171458.219195-8-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Abstract the memory type from the page_pool so we can later add support
for new memory types. Convert the page_pool to use the new netmem type
abstraction, rather than use struct page directly.
As of this patch the netmem type is a no-op abstraction: it's always a
struct page underneath. All the page pool internals are converted to
use struct netmem instead of struct page, and the page pool now exports
2 APIs:
1. The existing struct page API.
2. The new struct netmem API.
Keeping the existing API is transitional; we do not want to refactor all
the current drivers using the page pool at once.
The netmem abstraction is currently a no-op. The page_pool uses
page_to_netmem() to convert allocated pages to netmem, and uses
netmem_to_page() to convert the netmem back to pages to pass to mm APIs,
Follow up patches to this series add non-paged netmem support to the
page_pool. This change is factored out on its own to limit the code
churn to this 1 patch, for ease of code review.
Signed-off-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/20240628003253.1694510-6-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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This reverts commit a580ea994fd37f4105028f5a85c38ff6508a2b25.
This revert is to resolve Dragos's report of page_pool leak here:
https://lore.kernel.org/lkml/20240424165646.1625690-2-dtatulea@nvidia.com/
The reverted patch interacts very badly with commit 2cc3aeb5eccc ("skbuff:
Fix a potential race while recycling page_pool packets"). The reverted
commit hopes that the pp_recycle + is_pp_page variables do not change
between the skb_frag_ref and skb_frag_unref operation. If such a change
occurs, the skb_frag_ref/unref will not operate on the same reference type.
In the case of Dragos's report, the grabbed ref was a pp ref, but the unref
was a page ref, because the pp_recycle setting on the skb was changed.
Attempting to fix this issue on the fly is risky. Lets revert and I hope
to reland this with better understanding and testing to ensure we don't
regress some edge case while streamlining skb reffing.
Fixes: a580ea994fd3 ("net: mirror skb frag ref/unref helpers")
Reported-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Mina Almasry <almasrymina@google.com>
Link: https://lore.kernel.org/r/20240502175423.2456544-1-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Refactor some of the skb frag ref/unref helpers for improved clarity.
Implement napi_pp_get_page() to be the mirror counterpart of
napi_pp_put_page().
Implement skb_page_ref() to be the mirror of skb_page_unref().
Improve __skb_frag_ref() to become a mirror counterpart of
__skb_frag_unref(). Previously unref could handle pp & non-pp pages,
while the ref could only handle non-pp pages. Now both the ref & unref
helpers can correctly handle both pp & non-pp pages.
Now that __skb_frag_ref() can handle both pp & non-pp pages, remove
skb_pp_frag_ref(), and use __skb_frag_ref() instead. This lets us
remove pp specific handling from skb_try_coalesce.
Additionally, since __skb_frag_ref() can now handle both pp & non-pp
pages, a latent issue in skb_shift() should now be fixed. Previously
this function would do a non-pp ref & pp unref on potential pp frags
(fragfrom). After this patch, skb_shift() should correctly do a pp
ref/unref on pp frags.
Signed-off-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://lore.kernel.org/r/20240410190505.1225848-3-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Add a new header, linux/skbuff_ref.h, which contains all the skb_*_ref()
helpers. Many of the consumers of skbuff.h do not actually use any of
the skb ref helpers, and we can speed up compilation a bit by minimizing
this header file.
Additionally in the later patch in the series we add page_pool support
to skb_frag_ref(), which requires some page_pool dependencies. We can
now add these dependencies to skbuff_ref.h instead of a very ubiquitous
skbuff.h
Signed-off-by: Mina Almasry <almasrymina@google.com>
Link: https://lore.kernel.org/r/20240410190505.1225848-2-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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