[JFFS2] Optimise reading of eraseblock summary nodes
This improves the time to mount 512MiB of NAND flash on my OLPC prototype
by about 4%. We used to read the last page of the eraseblock twice -- once
to find the offset of the summary node, and again to actually _read_ the
summary node. Now we read the last page only once, and read more only if
we need to.
We also don't allocate a new buffer just for the summary code -- we use
the buffer which was already allocated for the scan. Better still, if the
'buffer' for the scan is actually just a pointer directly into NOR flash,
we use that too, avoiding the memcpy() which we used to do.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/fs/jffs2/scan.c b/fs/jffs2/scan.c
index 352ada8..2a24b44 100644
--- a/fs/jffs2/scan.c
+++ b/fs/jffs2/scan.c
@@ -306,11 +306,12 @@
return BLK_STATE_ALLDIRTY;
}
+/* Called with 'buf_size == 0' if buf is in fact a pointer _directly_ into
+ the flash, XIP-style */
static int jffs2_scan_eraseblock (struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
- unsigned char *buf, uint32_t buf_size, struct jffs2_summary *s) {
+ unsigned char *buf, uint32_t buf_size, struct jffs2_summary *s) {
struct jffs2_unknown_node *node;
struct jffs2_unknown_node crcnode;
- struct jffs2_sum_marker *sm;
uint32_t ofs, prevofs;
uint32_t hdr_crc, buf_ofs, buf_len;
int err;
@@ -344,32 +345,69 @@
#endif
if (jffs2_sum_active()) {
- sm = kmalloc(sizeof(struct jffs2_sum_marker), GFP_KERNEL);
- if (!sm) {
- return -ENOMEM;
- }
-
- err = jffs2_fill_scan_buf(c, (unsigned char *) sm, jeb->offset + c->sector_size -
- sizeof(struct jffs2_sum_marker), sizeof(struct jffs2_sum_marker));
- if (err) {
- kfree(sm);
- return err;
- }
-
- if (je32_to_cpu(sm->magic) == JFFS2_SUM_MAGIC ) {
- err = jffs2_sum_scan_sumnode(c, jeb, je32_to_cpu(sm->offset), &pseudo_random);
- if (err) {
- kfree(sm);
- return err;
+ struct jffs2_sum_marker *sm;
+ void *sumptr = NULL;
+ uint32_t sumlen;
+
+ if (!buf_size) {
+ /* XIP case. Just look, point at the summary if it's there */
+ sm = (void *)buf + jeb->offset - sizeof(*sm);
+ if (je32_to_cpu(sm->magic) == JFFS2_SUM_MAGIC) {
+ sumptr = buf + je32_to_cpu(sm->offset);
+ sumlen = c->sector_size - je32_to_cpu(sm->offset);
}
+ } else {
+ /* If NAND flash, read a whole page of it. Else just the end */
+ if (c->wbuf_pagesize)
+ buf_len = c->wbuf_pagesize;
+ else
+ buf_len = sizeof(*sm);
+
+ /* Read as much as we want into the _end_ of the preallocated buffer */
+ err = jffs2_fill_scan_buf(c, buf + buf_size - buf_len,
+ jeb->offset + c->sector_size - buf_len,
+ buf_len);
+ if (err)
+ return err;
+
+ sm = (void *)buf + buf_size - sizeof(*sm);
+ if (je32_to_cpu(sm->magic) == JFFS2_SUM_MAGIC) {
+ sumlen = c->sector_size - je32_to_cpu(sm->offset);
+ sumptr = buf + buf_size - sumlen;
+
+ /* Now, make sure the summary itself is available */
+ if (sumlen > buf_size) {
+ /* Need to kmalloc for this. */
+ sumptr = kmalloc(sumlen, GFP_KERNEL);
+ if (!sumptr)
+ return -ENOMEM;
+ memcpy(sumptr + sumlen - buf_len, buf + buf_size - buf_len, buf_len);
+ }
+ if (buf_len < sumlen) {
+ /* Need to read more so that the entire summary node is present */
+ err = jffs2_fill_scan_buf(c, sumptr,
+ jeb->offset + c->sector_size - sumlen,
+ sumlen - buf_len);
+ if (err)
+ return err;
+ }
+ }
+
}
- kfree(sm);
+ if (sumptr) {
+ err = jffs2_sum_scan_sumnode(c, jeb, sumptr, sumlen, &pseudo_random);
+ if (err)
+ return err;
+ if (buf_size && sumlen > buf_size)
+ kfree(sumptr);
+ }
}
buf_ofs = jeb->offset;
if (!buf_size) {
+ /* This is the XIP case -- we're reading _directly_ from the flash chip */
buf_len = c->sector_size;
} else {
buf_len = EMPTY_SCAN_SIZE(c->sector_size);