9p: fix readdir corner cases

The patch below also addresses a couple of other corner cases in readdir
seen with a large (e.g. 64k) msize.  I'm not sure what people think of
my co-opting of fid->aux here.  I'd be happy to rework if there's a better
way.

When the size of the user supplied buffer passed to readdir is smaller
than the data returned in one go by the 9P read request, v9fs_dir_readdir()
currently discards extra data so that, on the next call, a 9P read
request will be issued with offset < previous offset + bytes returned,
which voilates the constraint described in paragraph 3 of read(5) description.
This patch preseves the leftover data in fid->aux for use in the next call.

Signed-off-by: Jim Garlick <garlick@llnl.gov>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
This commit is contained in:
Eric Van Hensbergen 2009-11-02 08:39:28 -06:00
parent 2511cd0b3b
commit 3e2796a90c
3 changed files with 70 additions and 32 deletions

View File

@ -39,6 +39,24 @@
#include "v9fs_vfs.h"
#include "fid.h"
/**
* struct p9_rdir - readdir accounting
* @mutex: mutex protecting readdir
* @head: start offset of current dirread buffer
* @tail: end offset of current dirread buffer
* @buf: dirread buffer
*
* private structure for keeping track of readdir
* allocated on demand
*/
struct p9_rdir {
struct mutex mutex;
int head;
int tail;
uint8_t *buf;
};
/**
* dt_type - return file type
* @mistat: mistat structure
@ -70,57 +88,79 @@ static int v9fs_dir_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
int over;
struct p9_wstat st;
int err;
int err = 0;
struct p9_fid *fid;
int buflen;
char *statbuf;
int n, i = 0;
int reclen = 0;
struct p9_rdir *rdir;
P9_DPRINTK(P9_DEBUG_VFS, "name %s\n", filp->f_path.dentry->d_name.name);
fid = filp->private_data;
buflen = fid->clnt->msize - P9_IOHDRSZ;
statbuf = kmalloc(buflen, GFP_KERNEL);
if (!statbuf)
return -ENOMEM;
while (1) {
err = v9fs_file_readn(filp, statbuf, NULL, buflen,
fid->rdir_fpos);
if (err <= 0)
break;
/* allocate rdir on demand */
if (!fid->rdir) {
rdir = kmalloc(sizeof(struct p9_rdir) + buflen, GFP_KERNEL);
i = 0;
n = err;
while (i < n) {
err = p9stat_read(statbuf + i, buflen-i, &st,
fid->clnt->dotu);
if (rdir == NULL) {
err = -ENOMEM;
goto exit;
}
spin_lock(&filp->f_dentry->d_lock);
if (!fid->rdir) {
rdir->buf = (uint8_t *)rdir + sizeof(struct p9_rdir);
mutex_init(&rdir->mutex);
rdir->head = rdir->tail = 0;
fid->rdir = (void *) rdir;
rdir = NULL;
}
spin_unlock(&filp->f_dentry->d_lock);
kfree(rdir);
}
rdir = (struct p9_rdir *) fid->rdir;
err = mutex_lock_interruptible(&rdir->mutex);
while (err == 0) {
if (rdir->tail == rdir->head) {
err = v9fs_file_readn(filp, rdir->buf, NULL,
buflen, filp->f_pos);
if (err <= 0)
goto unlock_and_exit;
rdir->head = 0;
rdir->tail = err;
}
while (rdir->head < rdir->tail) {
err = p9stat_read(rdir->buf + rdir->head,
buflen - rdir->head, &st,
fid->clnt->dotu);
if (err) {
P9_DPRINTK(P9_DEBUG_VFS, "returned %d\n", err);
err = -EIO;
p9stat_free(&st);
goto free_and_exit;
goto unlock_and_exit;
}
i += st.size+2;
fid->rdir_fpos += st.size+2;
reclen = st.size+2;
over = filldir(dirent, st.name, strlen(st.name),
filp->f_pos, v9fs_qid2ino(&st.qid), dt_type(&st));
filp->f_pos += st.size+2;
p9stat_free(&st);
if (over) {
err = 0;
goto free_and_exit;
goto unlock_and_exit;
}
rdir->head += reclen;
filp->f_pos += reclen;
}
}
free_and_exit:
kfree(statbuf);
unlock_and_exit:
mutex_unlock(&rdir->mutex);
exit:
return err;
}

View File

@ -159,8 +159,7 @@ struct p9_client {
* @qid: the &p9_qid server identifier this handle points to
* @iounit: the server reported maximum transaction size for this file
* @uid: the numeric uid of the local user who owns this handle
* @aux: transport specific information (unused?)
* @rdir_fpos: tracks offset of file position when reading directory contents
* @rdir: readdir accounting structure (allocated on demand)
* @flist: per-client-instance fid tracking
* @dlist: per-dentry fid tracking
*
@ -174,9 +173,9 @@ struct p9_fid {
struct p9_qid qid;
u32 iounit;
uid_t uid;
void *aux;
int rdir_fpos;
void *rdir;
struct list_head flist;
struct list_head dlist; /* list of all fids attached to a dentry */
};

View File

@ -582,11 +582,9 @@ static struct p9_fid *p9_fid_create(struct p9_client *clnt)
memset(&fid->qid, 0, sizeof(struct p9_qid));
fid->mode = -1;
fid->rdir_fpos = 0;
fid->uid = current_fsuid();
fid->clnt = clnt;
fid->aux = NULL;
fid->rdir = NULL;
spin_lock_irqsave(&clnt->lock, flags);
list_add(&fid->flist, &clnt->fidlist);
spin_unlock_irqrestore(&clnt->lock, flags);
@ -609,6 +607,7 @@ static void p9_fid_destroy(struct p9_fid *fid)
spin_lock_irqsave(&clnt->lock, flags);
list_del(&fid->flist);
spin_unlock_irqrestore(&clnt->lock, flags);
kfree(fid->rdir);
kfree(fid);
}