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a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=xqWC_Br6kY4A:10 a=kj9zAlcOel0A:10 a=6UeiqGixMTsA:10 a=GoEa3M9JfhUA:10 a=VkNPw1HP01LnGYTKEx00:22 a=yPCof4ZbAAAA:8 a=vhSDPgbdtxYiioGkHJkA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: JKl7oNBk7DgnHpJGkFxo-j1NjMVj7EpE X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTE1MDAzMiBTYWx0ZWRfX7t+/mWtrJPnx YckdJ7981Nb5ps6m0pysGyEC3JMfM4Mtv4mrBTb053qgZp/NdXc3coPJLmJBlE2xF7PER87iEcE mw89kgstBVirpxAS1cHMUSTxp0YWqJZtWrK8us/K6FFg/EAb2sUTQU25RhZHCnTNAEJ0l1IaHZc 2Q6TpwpMi2x2Iq/glg2PcGipk/lt60PSgRkuoeh8KuIAp4528Qvi9Ee8YpdmOKQuayRzprkqZ6k GPesQjU52j/9HX3xvE1X+E9ZlM+P/HWrMdyXpbz279iqj6djhYuSNwkcNNq6ADPRZCezx0epcP4 EZjqyGC89HtHOQwqp7PMI8tynh7PELnhuELP2iW6L7jM5iKCa4IgaKn/U1/oOS1JQr/l2hnqNkL jBISlEwnpV3Fm9dWyYEiet9gWcOgPw== X-Proofpoint-GUID: JKl7oNBk7DgnHpJGkFxo-j1NjMVj7EpE On Mon, Nov 17, 2025 at 03:47:51PM +0000, Pedro Falcato wrote: > On Fri, Nov 14, 2025 at 05:53:18PM +0000, Lorenzo Stoakes wrote: > > Currently we set VM_SOFTDIRTY when a new mapping is set up (whether by > > establishing a new VMA, or via merge) as implemented in __mmap_complete() > > and do_brk_flags(). > > > > However, when performing a merge of existing mappings such as when > > performing mprotect(), we may lose the VM_SOFTDIRTY flag. > > Does it make sense to backport this to stable? A more minimal version, that is. No :) This has been subtly broken since forever. I don't think it warrants that and it'd require significant and risky changes to older kernels to even make it possible. It's more a biproduct of features added so let's fix this going forward. > > > > > This is because currently we simply ignore VM_SOFTDIRTY for the purposes of > > merge, so one VMA may possess the flag and another not, and whichever > > happens to be the target VMA will be the one upon which the merge is > > performed which may or may not have VM_SOFTDIRTY set. > > > > Now we have the concept of 'sticky' VMA flags, let's make VM_SOFTDIRTY one > > which solves this issue. > > > > Additionally update VMA userland tests to propagate changes. > > > > Suggested-by: Vlastimil Babka > > Signed-off-by: Lorenzo Stoakes > > Reviewed-by: Pedro Falcato Thanks! > > -- > Pedro Cheers, Lorenzo