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SubjectRE: 2.6.28-rc3 truncates nfsd results
Date


> From: J. Bruce Fields [mailto:bfields@fieldses.org]
> On Tue, Nov 04, 2008 at 01:27:23PM -0500, Doug Nazar wrote:
> > Commit 8d7c4203 "nfsd: fix failure to set eof in readdir in some situations"
> > breaks the nfsd server. Bisected it back to this commit and reverting it
> > fixes the problem.
> >
> > However, it only happens on certain machines even with the same kernel &
> > filesystem (ext3). I've two groups of similar computers, each group running
> > identical kernels. The ones listing only ~250 files are of course in error.
> > Eldritch is running 2.6.28-rc3 with that commit reverted. With 2.8.28-rc3 it
> > showed the incorrect number.
>
> Well, that's strange; it must be staring me in the face, but I don't see
> the problem (and can't reproduce it). Can you watch for the readdir
> with wireshark and see if it's returning an error on the readdir? Or is
> it just returning succesfully with eof set after the first ~250
> entries?

Ok, think I've figured it out.

The computers showing the issue are not using dir_index. This causes ext3 to read a block at a time, which then means we can end up
with buf.full==0 but not finished reading the directory. Before 8d7c4203, we'd always get called again because we never set
nfserr_eof which papered over it.

I think the correct solution is to move nfserr_eof into the loop and remove the buf.full check so that we loop until buf.used==0.
The following seems to do the right thing and reduces the network traffic since we now ensure each buffer is full.

Tested on an empty directory & large directory, eof is properly sent and no short buffers.

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 848a03e..4433c8f 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1875,11 +1875,11 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func,
return -ENOMEM;

offset = *offsetp;
- cdp->err = nfserr_eof; /* will be cleared on successful read */

while (1) {
unsigned int reclen;

+ cdp->err = nfserr_eof; /* will be cleared on successful read */
buf.used = 0;
buf.full = 0;

@@ -1912,9 +1912,6 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func,
de = (struct buffered_dirent *)((char *)de + reclen);
}
offset = vfs_llseek(file, 0, SEEK_CUR);
- cdp->err = nfserr_eof;
- if (!buf.full)
- break;
}

done:




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