Re: [PATCH 4/6] nfs: Teach NFS about swap cache pages

Peter Zijlstra
2006-08-25T20:21:01Z

On Fri, 2006-08-25 at 16:03 -0400, Trond Myklebust wrote:
> On Fri, 2006-08-25 at 17:37 +0200, Peter Zijlstra wrote:
> > Teach the NFS client how to treat PG_swapcache pages.
> >
> > Replace all occurences of page->index and page->mapping in the NFS client
> > with the new page_file_index() and page_file_mapping() functions.
> >
> > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> > ---
> > fs/nfs/dir.c | 4 ++--
> > fs/nfs/file.c | 6 +++---
> > fs/nfs/pagelist.c | 8 ++++----
> > fs/nfs/read.c | 10 +++++-----
> > fs/nfs/write.c | 34 +++++++++++++++++-----------------
> > 5 files changed, 31 insertions(+), 31 deletions(-)
>
> <snip>
>
> > @@ -821,7 +821,7 @@ int nfs_updatepage(struct file *file, st
> > unsigned int offset, unsigned int count)
> > {
> > struct nfs_open_context *ctx = (struct nfs_open_context *)file->private_data;
> > - struct inode *inode = page->mapping->host;
> > + struct inode *inode = page_file_mapping(page)->host;
> > struct nfs_page *req;
> > int status = 0;
> >
> > @@ -854,12 +854,12 @@ int nfs_updatepage(struct file *file, st
> > offset = 0;
> > if (unlikely(end_offs < 0)) {
> > /* Do nothing */
> > - } else if (page->index == end_index) {
> > + } else if (page_file_index(page) == end_index) {
>
> Is this necessary? When will we ever call nfs_updatepage() with a swap
> page? AFAICS, the swap stuff always uses page dirtying and (ugh)
> writepage().

Yes, swap uses writepage(), Nikita Danilov had a patch that did cluster
pageout using writepages(), however that tended to deadlock even on
local disk.

> > unsigned int pglen;
> > pglen = (unsigned int)(end_offs & (PAGE_CACHE_SIZE-1)) + 1;
> > if (count < pglen)
> > count = pglen;
> > - } else if (page->index < end_index)
> > + } else if (page_file_index(page) < end_index)
> > count = PAGE_CACHE_SIZE;
> > }
> >
> > Index: linux-2.6/fs/nfs/dir.c
> > ===================================================================
> > --- linux-2.6.orig/fs/nfs/dir.c
> > +++ linux-2.6/fs/nfs/dir.c
> > @@ -177,7 +177,7 @@ int nfs_readdir_filler(nfs_readdir_descr
> >
> > dfprintk(DIRCACHE, "NFS: %s: reading cookie %Lu into page %lu\n",
> > __FUNCTION__, (long long)desc->entry->cookie,
> > - page->index);
> > + page_file_index(page));
> >
> > again:
> > timestamp = jiffies;
> > @@ -201,7 +201,7 @@ int nfs_readdir_filler(nfs_readdir_descr
> > * Note: assumes we have exclusive access to this mapping either
> > * through inode->i_mutex or some other mechanism.
> > */
> > - if (page->index == 0)
> > + if (page_file_index(page) == 0)
> > invalidate_inode_pages2_range(inode->i_mapping, PAGE_CACHE_SIZE, -1);
> > unlock_page(page);
> > return 0;
>
> Why are we worried about the possibility of NFS readdir pages being swap
> pages?

Indiscriminate search and replace followed by a manual check for
correctness. They might not be needed, but they're not wrong either.

Would you prefer I take them out?