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>
diff --git a/fs/9p/vfs_dir.c b/fs/9p/vfs_dir.c
index cae53d4..15cce53 100644
--- a/fs/9p/vfs_dir.c
+++ b/fs/9p/vfs_dir.c
@@ -40,6 +40,24 @@
#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 @@
{
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;
}