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D19140.1775978985.diff
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D19140.1775978985.diff
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Index: head/stand/libsa/zfs/zfs.c
===================================================================
--- head/stand/libsa/zfs/zfs.c
+++ head/stand/libsa/zfs/zfs.c
@@ -363,51 +363,100 @@
vdev_read(vdev_t *vdev, void *priv, off_t offset, void *buf, size_t bytes)
{
int fd, ret;
- size_t res, size, remainder, rb_size, blksz;
- unsigned secsz;
- off_t off;
- char *bouncebuf, *rb_buf;
+ size_t res, head, tail, total_size, full_sec_size;
+ unsigned secsz, do_tail_read;
+ off_t start_sec;
+ char *outbuf, *bouncebuf;
fd = (uintptr_t) priv;
+ outbuf = (char *) buf;
bouncebuf = NULL;
ret = ioctl(fd, DIOCGSECTORSIZE, &secsz);
if (ret != 0)
return (ret);
- off = offset / secsz;
- remainder = offset % secsz;
- if (lseek(fd, off * secsz, SEEK_SET) == -1)
- return (errno);
+ /*
+ * Handling reads of arbitrary offset and size - multi-sector case
+ * and single-sector case.
+ *
+ * Multi-sector Case
+ * (do_tail_read = true if tail > 0)
+ *
+ * |<----------------------total_size--------------------->|
+ * | |
+ * |<--head-->|<--------------bytes------------>|<--tail-->|
+ * | | | |
+ * | | |<~full_sec_size~>| | |
+ * +------------------+ +------------------+
+ * | |0101010| . . . |0101011| |
+ * +------------------+ +------------------+
+ * start_sec start_sec + n
+ *
+ *
+ * Single-sector Case
+ * (do_tail_read = false)
+ *
+ * |<------total_size = secsz----->|
+ * | |
+ * |<-head->|<---bytes--->|<-tail->|
+ * +-------------------------------+
+ * | |0101010101010| |
+ * +-------------------------------+
+ * start_sec
+ */
+ start_sec = offset / secsz;
+ head = offset % secsz;
+ total_size = roundup2(head + bytes, secsz);
+ tail = total_size - (head + bytes);
+ do_tail_read = ((tail > 0) && (head + bytes > secsz));
+ full_sec_size = total_size;
+ if (head > 0)
+ full_sec_size -= secsz;
+ if (do_tail_read)
+ full_sec_size -= secsz;
- rb_buf = buf;
- rb_size = bytes;
- size = roundup2(bytes + remainder, secsz);
- blksz = size;
- if (remainder != 0 || size != bytes) {
+ /* Return of partial sector data requires a bounce buffer. */
+ if ((head > 0) || do_tail_read) {
bouncebuf = zfs_alloc(secsz);
if (bouncebuf == NULL) {
printf("vdev_read: out of memory\n");
return (ENOMEM);
}
- rb_buf = bouncebuf;
- blksz = rb_size - remainder;
}
- while (bytes > 0) {
- res = read(fd, rb_buf, rb_size);
- if (res != rb_size) {
+ if (lseek(fd, start_sec * secsz, SEEK_SET) == -1)
+ return (errno);
+
+ /* Partial data return from first sector */
+ if (head > 0) {
+ res = read(fd, bouncebuf, secsz);
+ if (res != secsz) {
ret = EIO;
goto error;
}
- if (bytes < blksz)
- blksz = bytes;
- if (bouncebuf != NULL)
- memcpy(buf, rb_buf + remainder, blksz);
- buf = (void *)((uintptr_t)buf + blksz);
- bytes -= blksz;
- remainder = 0;
- blksz = rb_size;
+ memcpy(outbuf, bouncebuf + head, secsz - head);
+ outbuf += secsz - head;
+ }
+
+ /* Full data return from read sectors */
+ if (full_sec_size > 0) {
+ res = read(fd, outbuf, full_sec_size);
+ if (res != full_sec_size) {
+ ret = EIO;
+ goto error;
+ }
+ outbuf += full_sec_size;
+ }
+
+ /* Partial data return from last sector */
+ if (do_tail_read) {
+ res = read(fd, bouncebuf, secsz);
+ if (res != secsz) {
+ ret = EIO;
+ goto error;
+ }
+ memcpy(outbuf, bouncebuf, secsz - tail);
}
ret = 0;

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