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charset="us-ascii" X-Rspamd-Queue-Id: 37E5E40003 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: xh7oxn5xqro9bnq7zui8o8qfmkxs6nm3 X-HE-Tag: 1710919470-390376 X-HE-Meta: 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 Re6eYndd TWfYuaeDemMCKnhnJ5BNQz2hZhpMLIYbKjAHLKPZIQRSFcsiWCp1oXEIAzeip09VR9w2SVn6rMT6X3sP57c+in11FtN5olNenchgoqkEAzoOL1VyTXi+CBwKqXDUSQ5uDWSs9U7Z5dhYzEWW7HAywDNgaDFdddiL3SCNlhV8k+r6nobeDiwuWcV8MhftdvNnK/LnWEG66QdqXRjzOL5oS+1s7j1j8pULxHfok/ezNHxgbvp9dF/XSDQ9NatQ+b22rbaXLuc1BBE1LjwKmSK6HZwsAoxOyNY3tmFbgwF97/vHIIiK0X9cl2agqGAfbluc3z750l7GpkkOnK/ZU8BX1MSC+VUj9BL+7qABXWzA5cBcMt1VP0gwB6keaA8iM/qOM99Tm X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: [..] > > > - /* map */ > > > - spin_lock(&tree->lock); > > > /* > > > - * The folio may have been dirtied again, invalidate the > > > - * possibly stale entry before inserting the new entry. > > > + * We finish initializing the entry while it's already in xarray. > > > + * This is safe because: > > > + * > > > + * 1. Concurrent stores and invalidations are excluded by folio lock. > > > + * > > > + * 2. Writeback is excluded by the entry not being on the LRU yet. > > > + * The publishing order matters to prevent writeback from seeing > > > + * an incoherent entry. > > > > As I mentioned before, writeback is also protected by the folio lock. > > Concurrent writeback will find the folio in the swapcache and abort. The > > fact that the entry is not on the LRU yet is just additional protection, > > so I don't think the publishing order actually matters here. Right? > > Right. This comment is explaining why this publishing order does not > matter. I think we are talking about the same thing here? The comment literally says "the publishing order matters.." :) I believe Johannes meant that we should only publish the entry to the LRU once it is fully initialized, to prevent writeback from using a partially initialized entry. What I am saying is that, even if we add a partially initialized entry to the zswap LRU, writeback will skip it anyway because the folio is locked in the swapcache. So basically I think the comment should say: /* * We finish initializing the entry while it's already in the * xarray. This is safe because the folio is locked in the swap * cache, which should protect against concurrent stores, * invalidations, and writeback. */ Johannes, what do you think?