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>

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>
Eric Van Hensbergen
1 parent 2511cd0b3b
Showing 3 changed files with 72 additions and 34 deletions Side-by-side Diff
fs/9p/vfs_dir.c
include/net/9p/client.h
net/9p/client.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;
 			}
+			reclen = st.size+2;
  
-			i += st.size+2;
-			fid->rdir_fpos += 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;
 }
  
@@ -159,8 +159,7 @@
  * @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_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 */
 };
@@ -582,11 +582,9 @@
  
 	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 @@
 	spin_lock_irqsave(&clnt->lock, flags);
 	list_del(&fid->flist);
 	spin_unlock_irqrestore(&clnt->lock, flags);
+	kfree(fid->rdir);
 	kfree(fid);
 }
...	...	@@ -40,6 +40,24 @@
40	40	#include "fid.h"
41	41
42	42	/**
	43	+ * struct p9_rdir - readdir accounting
	44	+ * @mutex: mutex protecting readdir
	45	+ * @head: start offset of current dirread buffer
	46	+ * @tail: end offset of current dirread buffer
	47	+ * @buf: dirread buffer
	48	+ *
	49	+ * private structure for keeping track of readdir
	50	+ * allocated on demand
	51	+ */
	52	+
	53	+struct p9_rdir {
	54	+ struct mutex mutex;
	55	+ int head;
	56	+ int tail;
	57	+ uint8_t *buf;
	58	+};
	59	+
	60	+/**
43	61	* dt_type - return file type
44	62	* @mistat: mistat structure
45	63	*
46	64
47	65
48	66
49	67
50	68
51	69
52	70
53	71
54	72
55	73
56	74
...	...	@@ -70,57 +88,79 @@
70	88	{
71	89	int over;
72	90	struct p9_wstat st;
73		- int err;
	91	+ int err = 0;
74	92	struct p9_fid *fid;
75	93	int buflen;
76		- char *statbuf;
77		- int n, i = 0;
	94	+ int reclen = 0;
	95	+ struct p9_rdir *rdir;
78	96
79	97	P9_DPRINTK(P9_DEBUG_VFS, "name %s\n", filp->f_path.dentry->d_name.name);
80	98	fid = filp->private_data;
81	99
82	100	buflen = fid->clnt->msize - P9_IOHDRSZ;
83		- statbuf = kmalloc(buflen, GFP_KERNEL);
84		- if (!statbuf)
85		- return -ENOMEM;
86	101
87		- while (1) {
88		- err = v9fs_file_readn(filp, statbuf, NULL, buflen,
89		- fid->rdir_fpos);
90		- if (err <= 0)
91		- break;
	102	+ /* allocate rdir on demand */
	103	+ if (!fid->rdir) {
	104	+ rdir = kmalloc(sizeof(struct p9_rdir) + buflen, GFP_KERNEL);
92	105
93		- i = 0;
94		- n = err;
95		- while (i < n) {
96		- err = p9stat_read(statbuf + i, buflen-i, &st,
97		- fid->clnt->dotu);
	106	+ if (rdir == NULL) {
	107	+ err = -ENOMEM;
	108	+ goto exit;
	109	+ }
	110	+ spin_lock(&filp->f_dentry->d_lock);
	111	+ if (!fid->rdir) {
	112	+ rdir->buf = (uint8_t *)rdir + sizeof(struct p9_rdir);
	113	+ mutex_init(&rdir->mutex);
	114	+ rdir->head = rdir->tail = 0;
	115	+ fid->rdir = (void *) rdir;
	116	+ rdir = NULL;
	117	+ }
	118	+ spin_unlock(&filp->f_dentry->d_lock);
	119	+ kfree(rdir);
	120	+ }
	121	+ rdir = (struct p9_rdir *) fid->rdir;
	122	+
	123	+ err = mutex_lock_interruptible(&rdir->mutex);
	124	+ while (err == 0) {
	125	+ if (rdir->tail == rdir->head) {
	126	+ err = v9fs_file_readn(filp, rdir->buf, NULL,
	127	+ buflen, filp->f_pos);
	128	+ if (err <= 0)
	129	+ goto unlock_and_exit;
	130	+
	131	+ rdir->head = 0;
	132	+ rdir->tail = err;
	133	+ }
	134	+
	135	+ while (rdir->head < rdir->tail) {
	136	+ err = p9stat_read(rdir->buf + rdir->head,
	137	+ buflen - rdir->head, &st,
	138	+ fid->clnt->dotu);
98	139	if (err) {
99	140	P9_DPRINTK(P9_DEBUG_VFS, "returned %d\n", err);
100	141	err = -EIO;
101	142	p9stat_free(&st);
102		- goto free_and_exit;
	143	+ goto unlock_and_exit;
103	144	}
	145	+ reclen = st.size+2;
104	146
105		- i += st.size+2;
106		- fid->rdir_fpos += st.size+2;
107		-
108	147	over = filldir(dirent, st.name, strlen(st.name),
109	148	filp->f_pos, v9fs_qid2ino(&st.qid), dt_type(&st));
110	149
111		- filp->f_pos += st.size+2;
112		-
113	150	p9stat_free(&st);
114	151
115	152	if (over) {
116	153	err = 0;
117		- goto free_and_exit;
	154	+ goto unlock_and_exit;
118	155	}
	156	+ rdir->head += reclen;
	157	+ filp->f_pos += reclen;
119	158	}
120	159	}
121	160
122		-free_and_exit:
123		- kfree(statbuf);
	161	+unlock_and_exit:
	162	+ mutex_unlock(&rdir->mutex);
	163	+exit:
124	164	return err;
125	165	}
126	166
...	...	@@ -159,8 +159,7 @@
159	159	* @qid: the &p9_qid server identifier this handle points to
160	160	* @iounit: the server reported maximum transaction size for this file
161	161	* @uid: the numeric uid of the local user who owns this handle
162		- * @aux: transport specific information (unused?)
163		- * @rdir_fpos: tracks offset of file position when reading directory contents
	162	+ * @rdir: readdir accounting structure (allocated on demand)
164	163	* @flist: per-client-instance fid tracking
165	164	* @dlist: per-dentry fid tracking
166	165	*
167	166
...	...	@@ -174,9 +173,9 @@
174	173	struct p9_qid qid;
175	174	u32 iounit;
176	175	uid_t uid;
177		- void *aux;
178	176
179		- int rdir_fpos;
	177	+ void *rdir;
	178	+
180	179	struct list_head flist;
181	180	struct list_head dlist; /* list of all fids attached to a dentry */
182	181	};
...	...	@@ -582,11 +582,9 @@
582	582
583	583	memset(&fid->qid, 0, sizeof(struct p9_qid));
584	584	fid->mode = -1;
585		- fid->rdir_fpos = 0;
586	585	fid->uid = current_fsuid();
587	586	fid->clnt = clnt;
588		- fid->aux = NULL;
589		-
	587	+ fid->rdir = NULL;
590	588	spin_lock_irqsave(&clnt->lock, flags);
591	589	list_add(&fid->flist, &clnt->fidlist);
592	590	spin_unlock_irqrestore(&clnt->lock, flags);
...	...	@@ -609,6 +607,7 @@
609	607	spin_lock_irqsave(&clnt->lock, flags);
610	608	list_del(&fid->flist);
611	609	spin_unlock_irqrestore(&clnt->lock, flags);
	610	+ kfree(fid->rdir);
612	611	kfree(fid);
613	612	}
614	613