udf_readatoffset: read through directory vnode, do not read > MAXBSIZE

Currently bread()-ing through device vnode with
(1) VMIO enabled,
(2) bo_bsize != DEV_BSIZE
(3) more than 1 block
results in data being incorrectly cached.
So instead a more common approach of using a vnode belonging to fs is now
employed.
Also, prevent attempt to bread more than MAXBSIZE bytes because of
adjustments made to account for offset that doesn't start on block
boundary.
Add expanded comments to explain the calculations.
Also drop unused inline function while here.

PR: kern/120967
PR: kern/129084

Reviewed by: scottl, kib
Approved by: jhb (mentor)

3 files changed, 23 insertions, 25 deletions

diff --git a/sys/fs/udf/udf.h b/sys/fs/udf/udf.h
index fe16bf5..c97e365 100644
--- a/sys/fs/udf/udf.h
+++ b/sys/fs/udf/udf.h
@@ -95,27 +95,12 @@ struct ifid {
 MALLOC_DECLARE(M_UDFFENTRY);
 
 static __inline int
-udf_readlblks(struct udf_mnt *udfmp, int sector, int size, struct buf **bp)
+udf_readdevblks(struct udf_mnt *udfmp, int sector, int size, struct buf **bp)
 {
 	return (RDSECTOR(udfmp->im_devvp, sector,
 			 (size + udfmp->bmask) & ~udfmp->bmask, bp));
 }
 
-static __inline int
-udf_readalblks(struct udf_mnt *udfmp, int lsector, int size, struct buf **bp)
-{
-	daddr_t rablock, lblk;
-	int rasize;
-
-	lblk = (lsector + udfmp->part_start) << (udfmp->bshift - DEV_BSHIFT);
-	rablock = (lblk + 1) << udfmp->bshift;
-	rasize = size;
-
-	return (breadn(udfmp->im_devvp, lblk,
-		       (size + udfmp->bmask) & ~udfmp->bmask,
-		       &rablock, &rasize, 1,  NOCRED, bp));
-}
-
 /*
  * Produce a suitable file number from an ICB.  The passed in ICB is expected
  * to be in little endian (meaning that it hasn't been swapped for big
diff --git a/sys/fs/udf/udf_vfsops.c b/sys/fs/udf/udf_vfsops.c
index b1a55d8..98a2a13 100644
--- a/sys/fs/udf/udf_vfsops.c
+++ b/sys/fs/udf/udf_vfsops.c
@@ -476,7 +476,7 @@ udf_mountfs(struct vnode *devvp, struct mount *mp)
 	 */
 	sector = le32toh(udfmp->root_icb.loc.lb_num) + udfmp->part_start;
 	size = le32toh(udfmp->root_icb.len);
-	if ((error = udf_readlblks(udfmp, sector, size, &bp)) != 0) {
+	if ((error = udf_readdevblks(udfmp, sector, size, &bp)) != 0) {
 		printf("Cannot read sector %d\n", sector);
 		goto bail;
 	}
@@ -794,7 +794,7 @@ udf_find_partmaps(struct udf_mnt *udfmp, struct logvol_desc *lvd)
 		 * XXX If reading the first Sparing Table fails, should look
 		 * for another table.
 		 */
-		if ((error = udf_readlblks(udfmp, le32toh(pms->st_loc[0]),
+		if ((error = udf_readdevblks(udfmp, le32toh(pms->st_loc[0]),
 					   le32toh(pms->st_size), &bp)) != 0) {
 			if (bp != NULL)
 				brelse(bp);
diff --git a/sys/fs/udf/udf_vnops.c b/sys/fs/udf/udf_vnops.c
index 4d5b3a3..5afb038 100644
--- a/sys/fs/udf/udf_vnops.c
+++ b/sys/fs/udf/udf_vnops.c
@@ -1296,16 +1296,20 @@ static int
 udf_readatoffset(struct udf_node *node, int *size, off_t offset,
     struct buf **bp, uint8_t **data)
 {
-	struct udf_mnt *udfmp;
-	struct file_entry *fentry = NULL;
+	struct udf_mnt *udfmp = node->udfmp;
+	struct vnode *vp = node->i_vnode;
+	struct file_entry *fentry;
 	struct buf *bp1;
 	uint32_t max_size;
 	daddr_t sector;
+	off_t off;
+	int adj_size;
 	int error;
 
-	udfmp = node->udfmp;
-
-	*bp = NULL;
+	/*
+	 * This call is made *not* only to detect UDF_INVALID_BMAP case,
+	 * max_size is used as an ad-hoc read-ahead hint for "normal" case.
+	 */
 	error = udf_bmap_internal(node, offset, &sector, &max_size);
 	if (error == UDF_INVALID_BMAP) {
 		/*
@@ -1323,9 +1327,18 @@ udf_readatoffset(struct udf_node *node, int *size, off_t offset,
 	/* Adjust the size so that it is within range */
 	if (*size == 0 || *size > max_size)
 		*size = max_size;
-	*size = min(*size, MAXBSIZE);
 
-	if ((error = udf_readlblks(udfmp, sector, *size + (offset & udfmp->bmask), bp))) {
+	/*
+	 * Because we will read starting at block boundary, we need to adjust
+	 * how much we need to read so that all promised data is in.
+	 * Also, we can't promise to read more than MAXBSIZE bytes starting
+	 * from block boundary, so adjust what we promise too.
+	 */
+	off = blkoff(udfmp, offset);
+	*size = min(*size, MAXBSIZE - off);
+	adj_size = (*size + off + udfmp->bmask) & ~udfmp->bmask;
+	*bp = NULL;
+	if ((error = bread(vp, lblkno(udfmp, offset), adj_size, NOCRED, bp))) {
 		printf("warning: udf_readlblks returned error %d\n", error);
 		/* note: *bp may be non-NULL */
 		return (error);