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Date: Sat, 18 Apr 2009 00:23:32 +0100
From: David Woodhouse <dwmw2@...radead.org>
To: Al Viro <viro@...IV.linux.org.uk>
Cc: hooanon05@...oo.co.jp, hch@...radead.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: Q: NFSD readdir in linux-2.6.28
On Fri, 2009-04-17 at 23:53 +0100, Al Viro wrote:
> On Fri, Apr 17, 2009 at 11:43:50PM +0100, Al Viro wrote:
> > On Fri, Apr 17, 2009 at 11:17:00PM +0100, David Woodhouse wrote:
> > > It sounds like the better answer is to just make sure i_mutex is held
> > > when nfsd_buffered_readdir() calls back into the provided filldir
> > > function (we could do it in the various filldir functions themselves,
> > > _if_ they call lookup_one_len(), but I think I prefer it this way --
> > > it's simpler). Patch below for comment.
> >
> > Umm... I can live with that, assuming that we don't have callbacks
> > that take i_mutex themselves. AFAICS, everything we call there is
> > either obviously not touching i_mutex or is already called while we
> > hold i_mutex elsewhere, but I'd appreciate if somebody actually
> > tested that sucker for different versions of protocol...
>
> BTW, why mess with taking i_mutex inside the inner loop and not
> immediately around it?
Or, to phrase my last response slightly differently... because I don't
like either of these two versions very much...
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index ab93fcf..0523e9f 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1885,9 +1885,10 @@ static int nfsd_buffered_filldir(void *__buf, const char *name, int namlen,
return 0;
}
-static int nfsd_buffered_readdir(struct file *file, filldir_t func,
- struct readdir_cd *cdp, loff_t *offsetp)
+static __be32 nfsd_buffered_readdir(struct file *file, filldir_t func,
+ struct readdir_cd *cdp, loff_t *offsetp)
{
+ struct inode *dir_inode = file->f_path.dentry->d_inode;
struct readdir_data buf;
struct buffered_dirent *de;
int host_err;
@@ -1896,7 +1897,7 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func,
buf.dirent = (void *)__get_free_page(GFP_KERNEL);
if (!buf.dirent)
- return -ENOMEM;
+ return nfserrno(-ENOMEM);
offset = *offsetp;
@@ -1912,23 +1913,37 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func,
host_err = 0;
if (host_err < 0)
- break;
+ goto done;
size = buf.used;
if (!size)
- break;
+ goto done;
de = (struct buffered_dirent *)buf.dirent;
+
+ host_err = mutex_lock_killable(&dir_inode->i_mutex);
+ if (host_err)
+ goto done;
+
while (size > 0) {
+
+ int finished;
+
offset = de->offset;
+ /*
+ * Various filldir functions may end up calling back
+ * into lookup_one_len() and the file system's
+ * ->lookup() method. These expect i_mutex to be held.
+ */
+
if (func(cdp, de->name, de->namlen, de->offset,
de->ino, de->d_type))
- goto done;
-
+ goto done_unlock;
+
if (cdp->err != nfs_ok)
- goto done;
+ goto done_unlock;
reclen = ALIGN(sizeof(*de) + de->namlen,
sizeof(u64));
@@ -1937,6 +1952,8 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func,
}
offset = vfs_llseek(file, 0, SEEK_CUR);
}
+ done_unlock:
+ mutex_unlock(&dir_inode->i_mutex);
done:
free_page((unsigned long)(buf.dirent));
====================================================================
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index ab93fcf..915a47c 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1885,8 +1885,8 @@ static int nfsd_buffered_filldir(void *__buf, const char *name, int namlen,
return 0;
}
-static int nfsd_buffered_readdir(struct file *file, filldir_t func,
- struct readdir_cd *cdp, loff_t *offsetp)
+static __be32 nfsd_buffered_readdir(struct file *file, filldir_t func,
+ struct readdir_cd *cdp, loff_t *offsetp)
{
struct readdir_data buf;
struct buffered_dirent *de;
@@ -1896,11 +1896,12 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func,
buf.dirent = (void *)__get_free_page(GFP_KERNEL);
if (!buf.dirent)
- return -ENOMEM;
+ return nfserrno(-ENOMEM);
offset = *offsetp;
while (1) {
+ struct inode *dir_inode = file->f_path.dentry->d_inode;
unsigned int reclen;
cdp->err = nfserr_eof; /* will be cleared on successful read */
@@ -1920,24 +1921,42 @@ static int nfsd_buffered_readdir(struct file *file, filldir_t func,
break;
de = (struct buffered_dirent *)buf.dirent;
+
+ host_err = mutex_lock_killable(&dir_inode->i_mutex);
+ if (host_err)
+ break;
+
while (size > 0) {
+ int finished;
+
offset = de->offset;
+ /*
+ * Various filldir functions may end up calling back
+ * into lookup_one_len() and the file system's
+ * ->lookup() method. These expect i_mutex to be held.
+ */
+
if (func(cdp, de->name, de->namlen, de->offset,
de->ino, de->d_type))
- goto done;
-
+ goto done_unlock;
+
if (cdp->err != nfs_ok)
- goto done;
+ goto done_unlock;
reclen = ALIGN(sizeof(*de) + de->namlen,
sizeof(u64));
size -= reclen;
de = (struct buffered_dirent *)((char *)de + reclen);
}
+ mutex_unlock(&dir_inode->i_mutex);
offset = vfs_llseek(file, 0, SEEK_CUR);
- }
+ continue;
+ done_unlock:
+ mutex_unlock(&dir_inode->i_mutex);
+ break;
+ }
done:
free_page((unsigned long)(buf.dirent));
--
dwmw2
--
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