Re: infinite loop? with mmap, nfs, pwrite, O_DIRECT

[Trond Myklebust <trond.myklebust@fys.uio.no>]

On Mon, 2005-11-21 at 13:39 -0800, Kenny Simpson wrote:
> With gentle beating by a clue-stick from Andrew.. I can run the same test on ext3...
> 
> ext3 is happy...
> 
> open("/data/foo", O_RDWR|O_CREAT|O_TRUNC|O_DIRECT|O_LARGEFILE, 0666) = 3
> pwrite(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 4096, 4299161600) = 4096
> mmap2(NULL, 2097152, PROT_READ|PROT_WRITE, MAP_SHARED, 3, 0x100200) = 0xb7c7f000
> pwrite(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 4096, 4301258752) = 4096
> exit_group(0)                           = ?
> 
> 
> but NFS is still unhappy....
> 
> open("/mnt/bar", O_RDWR|O_CREAT|O_TRUNC|O_DIRECT|O_LARGEFILE, 0666) = 3
> pwrite(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 4096, 4299161600) = 4096
> mmap2(NULL, 2097152, PROT_READ|PROT_WRITE, MAP_SHARED, 3, 0x100200) = 0xb7bc2000
> pwrite(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 4096, 4301258752  <never
> returns>

Ah... It is the pwrite() _after_ the call to mmap() that fails....

OK, does the following patch fix it?

Cheers,
  Trond
-------------
NFS: O_DIRECT cannot call invalidate_inode_pages2().

 Anything that calls lock_page() should be avoided in O_DIRECT, however
 we should be able to call invalidate_inode_pages() since that doesn't
 wait on the page lock.

 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
---

 fs/nfs/direct.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index a2d2814..ef299f8 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -774,7 +774,7 @@ nfs_file_direct_write(struct kiocb *iocb
 
 	retval = nfs_direct_write(inode, ctx, &iov, pos, 1);
 	if (mapping->nrpages)
-		invalidate_inode_pages2(mapping);
+		invalidate_inode_pages(mapping);
 	if (retval > 0)
 		*ppos = pos + retval;