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net/smc: cap allocation order for SMC-R physically contiguous buffers

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The alloc_pages() cannot satisfy requests exceeding MAX_PAGE_ORDER,
and attempting such allocations will lead to guaranteed failures
and potential kernel warnings.

For SMCR_PHYS_CONT_BUFS, cap the allocation order to MAX_PAGE_ORDER.
This ensures the attempts to allocate the largest possible physically
contiguous chunk succeed, instead of failing with an invalid order.
This also avoids redundant "try-fail-degrade" cycles in
__smc_buf_create().

For SMCR_MIXED_BUFS, no cap is needed: if the order exceeds
MAX_PAGE_ORDER, alloc_pages() will silently fail (__GFP_NOWARN)
and automatically fall back to virtual memory.

Signed-off-by: D. Wythe <alibuda@linux.alibaba.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Sidraya Jayagond <sidraya@linux.ibm.com>
Link: https://patch.msgid.link/20260429021637.21815-1-alibuda@linux.alibaba.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
D. Wythe 2026-04-29 10:16:37 +08:00 committed by Jakub Kicinski
parent 6855a52318
commit 4cc5130ee8
1 changed files with 4 additions and 0 deletions
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4
net/smc/smc_core.c
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@ -2440,6 +2440,10 @@ static int __smc_buf_create(struct smc_sock *smc, bool is_smcd, bool is_rmb)
/* use socket send buffer size (w/o overhead) as start value */
bufsize = smc->sk.sk_sndbuf / 2;
/* limit bufsize for physically contiguous buffers */
if (!is_smcd && lgr->buf_type == SMCR_PHYS_CONT_BUFS)
bufsize = min_t(int, bufsize, PAGE_SIZE << MAX_PAGE_ORDER);
for (bufsize_comp = smc_compress_bufsize(bufsize, is_smcd, is_rmb);
bufsize_comp >= 0; bufsize_comp--) {
if (is_rmb) {