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NFS: swap-out must always use STABLE writes.
stable inclusion from stable-4.19.238 commit 194722a9e87eaf7fc3af9a38f1330a224342e730 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5A6BA CVE: NA -------------------------------- [ Upstream commit c265de257f558a05c1859ee9e3fed04883b9ec0e ] The commit handling code is not safe against memory-pressure deadlocks when writing to swap. In particular, nfs_commitdata_alloc() blocks indefinitely waiting for memory, and this can consume all available workqueue threads. swap-out most likely uses STABLE writes anyway as COND_STABLE indicates that a stable write should be used if the write fits in a single request, and it normally does. However if we ever swap with a small wsize, or gather unusually large numbers of pages for a single write, this might change. For safety, make it explicit in the code that direct writes used for swap must always use FLUSH_STABLE. Signed-off-by:NeilBrown <neilb@suse.de> Signed-off-by:
Trond Myklebust <trond.myklebust@hammerspace.com> Signed-off-by:
Sasha Levin <sashal@kernel.org> Signed-off-by:
Yongqiang Liu <liuyongqiang13@huawei.com>
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