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See http://www.infradead.org/rpr.html X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C564540002 X-Stat-Signature: wid31i6z9izymz1ts1nb4swmrjm69yib X-HE-Tag: 1790588662-556312 X-HE-Meta: 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 NAiQDNcd 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 28, 2026 at 10:18:36AM +0200, Alexandre Ghiti wrote: > bio_issue_as_root_blkg() issues every REQ_SWAP bio as root, bypassing > the cgroup IO controllers, because reclaim cannot stall indefinitely on > swap writes. Some swap writes are not urgent though: zswap writeback is > best effort. > > Such a bio cannot simply drop REQ_SWAP: dm-crypt and dm-thin rely on it > for limit_swap_bios, which caps in-flight swap bios to avoid a memory > deadlock, see commit a666e5c05e7c ("dm: fix deadlock when swapping to > encrypted device"). Is that true? REQ_BACKGROUND very much implies the I/O can the throttled and thus better not be foreground paging, and thus the caller should be able to tolerate a failure.