On Wed, 1 Dec 2010, Linus Torvalds wrote: > --00032557542a0c5e6004965ba615 > Content-Type: text/plain; charset=ISO-8859-1 > > On Wed, Dec 1, 2010 at 7:36 AM, Trond Myklebust > <Trond.Myklebust@xxxxxxxxxx> wrote: > > > > We need to ensure that the entries in the nfs_cache_array get cleared > > when the page is removed from the page cache. To do so, we use the > > releasepage address_space operation (which also requires us to set > > the Pg_private flag). > > So I really think that the whole "releasepage" use in NFS is simply > overly complicated and was obviously too subtle. > > The whole need for odd return values, for the page lock, and for the > addition of clearing the up-to-date bit comes from the fact that this > wasn't really what releasepage was designed for. > > 'releasepage' was really designed for the filesystem having its own > version of 'try_to_free_buffers()', which is just an optimistic "ok, > we may be releasing this page, so try to get rid of any IO structures > you have cached". It wasn't really a memory management thing. > > And the thing is, it looks trivial to do the memory management > approach by adding a new callback that gets called after the page is > actually removed from the page cache. If we do that, then there are no > races with any other users, since we remove things from the page cache > atomically wrt page cache lookup. So the need for playing games with > page locking and 'uptodate' simply goes away. As does the PG_private > thing or the interaction with invalidatepage() etc. > > So this is a TOTALLY UNTESTED trivial patch that just adds another > callback. Does this work? I dunno. But I get the feeling that instead > of having NFS work around the odd semantics that don't actually match > what NFS wants, introducing a new callback with much simpler semantics > would be simpler for everybody, and avoid the need for subtle code. > > Hmm? > > Linus > > --00032557542a0c5e6004965ba615 > Content-Type: text/x-patch; charset=US-ASCII; name="patch.diff" > Content-Disposition: attachment; filename="patch.diff" > Content-Transfer-Encoding: base64 > X-Attachment-Id: f_gh6f5ghm0 > > IGluY2x1ZGUvbGludXgvZnMuaCB8ICAgIDEgKwogbW0vdm1zY2FuLmMgICAgICAgIHwgICAgMyAr > KysKIDIgZmlsZXMgY2hhbmdlZCwgNCBpbnNlcnRpb25zKCspLCAwIGRlbGV0aW9ucygtKQoKZGlm > ZiAtLWdpdCBhL2luY2x1ZGUvbGludXgvZnMuaCBiL2luY2x1ZGUvbGludXgvZnMuaAppbmRleCBj > OWUwNmNjLi4wOTBmMGVhIDEwMDY0NAotLS0gYS9pbmNsdWRlL2xpbnV4L2ZzLmgKKysrIGIvaW5j > bHVkZS9saW51eC9mcy5oCkBAIC02MDIsNiArNjAyLDcgQEAgc3RydWN0IGFkZHJlc3Nfc3BhY2Vf > b3BlcmF0aW9ucyB7CiAJc2VjdG9yX3QgKCpibWFwKShzdHJ1Y3QgYWRkcmVzc19zcGFjZSAqLCBz > ZWN0b3JfdCk7CiAJdm9pZCAoKmludmFsaWRhdGVwYWdlKSAoc3RydWN0IHBhZ2UgKiwgdW5zaWdu > ZWQgbG9uZyk7CiAJaW50ICgqcmVsZWFzZXBhZ2UpIChzdHJ1Y3QgcGFnZSAqLCBnZnBfdCk7CisJ > dm9pZCAoKmZyZWVwYWdlKShzdHJ1Y3QgcGFnZSAqKTsKIAlzc2l6ZV90ICgqZGlyZWN0X0lPKShp > bnQsIHN0cnVjdCBraW9jYiAqLCBjb25zdCBzdHJ1Y3QgaW92ZWMgKmlvdiwKIAkJCWxvZmZfdCBv > ZmZzZXQsIHVuc2lnbmVkIGxvbmcgbnJfc2Vncyk7CiAJaW50ICgqZ2V0X3hpcF9tZW0pKHN0cnVj > dCBhZGRyZXNzX3NwYWNlICosIHBnb2ZmX3QsIGludCwKZGlmZiAtLWdpdCBhL21tL3Ztc2Nhbi5j > IGIvbW0vdm1zY2FuLmMKaW5kZXggZDMxZDdjZS4uMWFjY2IwMSAxMDA2NDQKLS0tIGEvbW0vdm1z > Y2FuLmMKKysrIGIvbW0vdm1zY2FuLmMKQEAgLTQ5OSw2ICs0OTksOSBAQCBzdGF0aWMgaW50IF9f > cmVtb3ZlX21hcHBpbmcoc3RydWN0IGFkZHJlc3Nfc3BhY2UgKm1hcHBpbmcsIHN0cnVjdCBwYWdl > ICpwYWdlKQogCQltZW1fY2dyb3VwX3VuY2hhcmdlX2NhY2hlX3BhZ2UocGFnZSk7CiAJfQogCisJ > aWYgKG1hcHBpbmctPmFfb3BzLT5mcmVlcGFnZSkKKwkJbWFwcGluZy0+YV9vcHMtPmZyZWVwYWdl > KHBhZ2UpOworCiAJcmV0dXJuIDE7CiAKIGNhbm5vdF9mcmVlOgo= > --00032557542a0c5e6004965ba615-- This violates the "Really. Don't send patches as attachments." lkml-faq set forth by yourself ;) Am I the only one who still uses a mail reader that doesn't decode mime by default? Maybe it's time to move on... Thanks, Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
