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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: David Howells <dhowells@redhat.com>,
	linux-cachefs@redhat.com, Jeff Layton <jlayton@kernel.org>,
	Marc Dionne <marc.dionne@auristor.com>,
	linux-afs@lists.infradead.org,
	Trond Myklebust <trondmy@hammerspace.com>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	Steve French <sfrench@samba.org>,
	Dominique Martinet <asmadeus@codewreck.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Omar Sandoval <osandov@osandov.com>,
	JeffleXu <jefflexu@linux.alibaba.com>,
	"open list:NFS, SUNRPC, AND..." <linux-nfs@vger.kernel.org>,
	CIFS <linux-cifs@vger.kernel.org>,
	ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 56/68] afs: Handle len being extending over page end in write_begin/write_end
Date: Thu, 16 Dec 2021 11:46:18 -0800	[thread overview]
Message-ID: <CAHk-=wh2dr=NgVSVj0sw-gSuzhxhLRV5FymfPS146zGgF4kBjA@mail.gmail.com> (raw)
In-Reply-To: <YbuTaRbNUAJx5xOA@casper.infradead.org>

On Thu, Dec 16, 2021 at 11:28 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> Since ->write_begin is the place where we actually create folios, it
> needs to know what size folio to create.  Unless you'd rather we do
> something to actually create the folio before calling ->write_begin?

I don't think we can create a folio before that, because the
filesystem may not even want a folio (think persistent memory or
whatever).

Honestly, I think you need to describe more what you actually want to
happen. Because generic_perform_write() has already decided to use a
PAGE_SIZE by the time write_begin() is called,

Right now the world order is "we chunk things by PAGE_SIZE", and
that's just how it is.

I can see other options - like the filesystem passing in the chunk
size when it calls generic_perform_write().

Or we make the rule be that ->write_begin() simply always is given the
whole area, and the filesystem can decide how it wants to chunk things
up, and return the size of the write chunk in the status (rather than
the current "success or error").

But at no point will this *EVER* be a "afs will limit the size to the
folio size" issue. Nothing like that will ever make sense. Allowing
bigger chunks will not be about any fscache issues, it will be about
every single filesystem that uses generic_perform_write().

So I will NAK these patches by David, because they are fundamentally
wrong, whichever way we turn. Any "write in bigger chunks" patch will
be something else entirely.

                 Linus

  reply	other threads:[~2021-12-16 19:54 UTC|newest]

Thread overview: 84+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-16 16:05 [PATCH v3 00/68] fscache, cachefiles: Rewrite David Howells
2021-12-16 16:05 ` [PATCH v3 01/68] fscache, cachefiles: Disable configuration David Howells
2021-12-16 16:06 ` [PATCH v3 02/68] cachefiles: Delete the cachefiles driver pending rewrite David Howells
2021-12-16 16:06 ` [PATCH v3 03/68] fscache: Remove the contents of the fscache driver, " David Howells
2021-12-16 16:06 ` [PATCH v3 04/68] netfs: Display the netfs inode number in the netfs_read tracepoint David Howells
2021-12-16 16:06 ` [PATCH v3 05/68] netfs: Pass a flag to ->prepare_write() to say if there's no alloc'd space David Howells
2021-12-16 16:06 ` [PATCH v3 06/68] fscache: Introduce new driver David Howells
2021-12-16 16:07 ` [PATCH v3 07/68] fscache: Implement a hash function David Howells
2021-12-16 16:07 ` [PATCH v3 08/68] fscache: Implement cache registration David Howells
2021-12-16 16:07 ` [PATCH v3 09/68] fscache: Implement volume registration David Howells
2021-12-16 16:08 ` [PATCH v3 10/68] fscache: Implement cookie registration David Howells
2021-12-16 16:08 ` [PATCH v3 11/68] fscache: Implement cache-level access helpers David Howells
2021-12-16 16:09 ` [PATCH v3 12/68] fscache: Implement volume-level " David Howells
2021-12-16 16:09 ` [PATCH v3 13/68] fscache: Implement cookie-level " David Howells
2021-12-16 16:09 ` [PATCH v3 14/68] fscache: Implement functions add/remove a cache David Howells
2021-12-16 16:09 ` [PATCH v3 15/68] fscache: Provide and use cache methods to lookup/create/free a volume David Howells
2021-12-16 16:10 ` [PATCH v3 16/68] fscache: Add a function for a cache backend to note an I/O error David Howells
2021-12-16 16:10 ` [PATCH v3 17/68] fscache: Implement simple cookie state machine David Howells
2021-12-17 19:07   ` Jeff Layton
2021-12-17 19:45   ` David Howells
2021-12-16 16:11 ` [PATCH v3 18/68] fscache: Implement cookie user counting and resource pinning David Howells
2021-12-17 19:42   ` Jeff Layton
2021-12-17 20:43   ` David Howells
2021-12-16 16:11 ` [PATCH v3 19/68] fscache: Implement cookie invalidation David Howells
2021-12-16 16:11 ` [PATCH v3 20/68] fscache: Provide a means to begin an operation David Howells
2021-12-16 16:11 ` [PATCH v3 21/68] fscache: Count data storage objects in a cache David Howells
2021-12-16 16:12 ` [PATCH v3 22/68] fscache: Provide read/write stat counters for the cache David Howells
2021-12-16 16:12 ` [PATCH v3 23/68] fscache: Provide a function to let the netfs update its coherency data David Howells
2021-12-16 16:13 ` [PATCH v3 24/68] netfs: Pass more information on how to deal with a hole in the cache David Howells
2021-12-16 16:13 ` [PATCH v3 25/68] fscache: Implement raw I/O interface David Howells
2021-12-16 16:13 ` [PATCH v3 26/68] fscache: Implement higher-level write " David Howells
2021-12-16 16:14 ` [PATCH v3 27/68] vfs, fscache: Implement pinning of cache usage for writeback David Howells
2021-12-16 16:14 ` [PATCH v3 28/68] fscache: Provide a function to note the release of a page David Howells
2021-12-16 16:14 ` [PATCH v3 29/68] fscache: Provide a function to resize a cookie David Howells
2021-12-16 16:15 ` [PATCH v3 30/68] cachefiles: Introduce rewritten driver David Howells
2021-12-16 16:15 ` [PATCH v3 31/68] cachefiles: Define structs David Howells
2021-12-16 16:15 ` [PATCH v3 32/68] cachefiles: Add some error injection support David Howells
2021-12-16 16:15 ` [PATCH v3 33/68] cachefiles: Add a couple of tracepoints for logging errors David Howells
2021-12-16 16:16 ` [PATCH v3 34/68] cachefiles: Add cache error reporting macro David Howells
2021-12-16 16:16 ` [PATCH v3 35/68] cachefiles: Add security derivation David Howells
2021-12-16 16:16 ` [PATCH v3 36/68] cachefiles: Register a miscdev and parse commands over it David Howells
2021-12-16 16:16 ` [PATCH v3 37/68] cachefiles: Provide a function to check how much space there is David Howells
2021-12-16 16:16 ` [PATCH v3 38/68] vfs, cachefiles: Mark a backing file in use with an inode flag David Howells
2021-12-16 16:16 ` [PATCH v3 39/68] cachefiles: Implement a function to get/create a directory in the cache David Howells
2021-12-16 16:17 ` [PATCH v3 40/68] cachefiles: Implement cache registration and withdrawal David Howells
2021-12-16 16:17 ` [PATCH v3 41/68] cachefiles: Implement volume support David Howells
2021-12-16 16:17 ` [PATCH v3 42/68] cachefiles: Add tracepoints for calls to the VFS David Howells
2021-12-16 16:18 ` [PATCH v3 43/68] cachefiles: Implement object lifecycle funcs David Howells
2021-12-16 16:18 ` [PATCH v3 44/68] cachefiles: Implement key to filename encoding David Howells
2021-12-16 16:18 ` [PATCH v3 45/68] cachefiles: Implement metadata/coherency data storage in xattrs David Howells
2021-12-16 16:19 ` [PATCH v3 46/68] cachefiles: Mark a backing file in use with an inode flag David Howells
2021-12-16 16:19 ` [PATCH v3 47/68] cachefiles: Implement culling daemon commands David Howells
2021-12-16 16:19 ` [PATCH v3 48/68] cachefiles: Implement backing file wrangling David Howells
2021-12-16 16:20 ` [PATCH v3 49/68] cachefiles: Implement begin and end I/O operation David Howells
2021-12-16 16:20 ` [PATCH v3 50/68] cachefiles: Implement cookie resize for truncate David Howells
2021-12-16 16:20 ` [PATCH v3 51/68] cachefiles: Implement the I/O routines David Howells
2021-12-16 16:20 ` [PATCH v3 52/68] fscache, cachefiles: Store the volume coherency data David Howells
2021-12-16 16:20 ` [PATCH v3 53/68] cachefiles: Allow cachefiles to actually function David Howells
2021-12-16 16:21 ` [PATCH v3 54/68] fscache, cachefiles: Display stats of no-space events David Howells
2021-12-16 16:21 ` [PATCH v3 55/68] fscache, cachefiles: Display stat of culling events David Howells
2021-12-16 16:21 ` [PATCH v3 56/68] afs: Handle len being extending over page end in write_begin/write_end David Howells
2021-12-16 16:31   ` Linus Torvalds
2021-12-16 19:28     ` Matthew Wilcox
2021-12-16 19:46       ` Linus Torvalds [this message]
2021-12-16 20:20         ` Matthew Wilcox
2021-12-16 21:17       ` David Howells
2021-12-16 16:47   ` David Howells
2021-12-16 16:22 ` [PATCH v3 57/68] afs: Fix afs_write_end() to handle len > page size David Howells
2021-12-16 16:27   ` Linus Torvalds
2021-12-16 16:22 ` [PATCH v3 58/68] afs: Convert afs to use the new fscache API David Howells
2021-12-16 16:22 ` [PATCH v3 59/68] afs: Copy local writes to the cache when writing to the server David Howells
2021-12-16 16:22 ` [PATCH v3 60/68] afs: Skip truncation on the server of data we haven't written yet David Howells
2021-12-16 16:23 ` [PATCH v3 61/68] 9p: Use fscache indexing rewrite and reenable caching David Howells
2021-12-16 16:23 ` [PATCH v3 62/68] 9p: Copy local writes to the cache when writing to the server David Howells
2021-12-16 16:23 ` [PATCH v3 63/68] nfs: Convert to new fscache volume/cookie API David Howells
2021-12-17 12:53   ` David Wysochanski
2021-12-17 13:21   ` David Howells
2021-12-17 13:35     ` David Wysochanski
2021-12-16 16:24 ` [PATCH v3 64/68] nfs: Implement cache I/O by accessing the cache directly David Howells
2021-12-16 16:24 ` [PATCH v3 65/68] cifs: Support fscache indexing rewrite (untested) David Howells
2021-12-16 16:24 ` [PATCH v3 66/68] ceph: conversion to new fscache API David Howells
2021-12-16 16:25 ` [PATCH v3 67/68] ceph: add fscache writeback support David Howells
2021-12-16 16:25 ` [PATCH v3 68/68] fscache: Rewrite documentation David Howells
2021-12-17 20:13 ` [PATCH v3 00/68] fscache, cachefiles: Rewrite Jeff Layton

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