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authorDavid Howells <dhowells@redhat.com>2021-08-27 15:19:34 +0100
committerDavid Howells <dhowells@redhat.com>2022-01-10 11:53:25 +0000
commit16f2f4e679cfdaa9552574484f104014908a76c6 (patch)
treec8fef29e9ecfbff27b6a2e5736766f3c40f0c986 /fs/xfs
parenta6b5a28eb56c3f4988f7ff5290b954ba296e309a (diff)
nfs: Implement cache I/O by accessing the cache directly
Move NFS to using fscache DIO API instead of the old upstream I/O API as that has been removed. This is a stopgap solution as the intention is that at sometime in the future, the cache will move to using larger blocks and won't be able to store individual pages in order to deal with the potential for data corruption due to the backing filesystem being able insert/remove bridging blocks of zeros into its extent list[1]. NFS then reads and writes cache pages synchronously and one page at a time. The preferred change would be to use the netfs lib, but the new I/O API can be used directly. It's just that as the cache now needs to track data for itself, caching blocks may exceed page size... This code is somewhat borrowed from my "fallback I/O" patchset[2]. Changes ======= ver #3: - Restore lost =n fallback for nfs_fscache_release_page()[2]. Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Dave Wysochanski <dwysocha@redhat.com> Acked-by: Jeff Layton <jlayton@kernel.org> cc: Trond Myklebust <trond.myklebust@hammerspace.com> cc: Anna Schumaker <anna.schumaker@netapp.com> cc: linux-nfs@vger.kernel.org cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/YO17ZNOcq+9PajfQ@mit.edu [1] Link: https://lore.kernel.org/r/202112100957.2oEDT20W-lkp@intel.com/ [2] Link: https://lore.kernel.org/r/163189108292.2509237.12615909591150927232.stgit@warthog.procyon.org.uk/ [2] Link: https://lore.kernel.org/r/163906981318.143852.17220018647843475985.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967184451.1823006.6450645559828329590.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021577632.640689.11069627070150063812.stgit@warthog.procyon.org.uk/ # v4
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