[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>

3 files changed, 64 insertions, 49 deletions

diff --git a/fs/jffs2/scan.c b/fs/jffs2/scan.c
index 352ada892f3e..2a24b44662bb 100644
--- a/fs/jffs2/scan.c
+++ b/fs/jffs2/scan.c
@@ -306,11 +306,12 @@ int jffs2_scan_classify_jeb(struct jffs2_sb_info *c, struct jffs2_eraseblock *je
                 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 @@ static int jffs2_scan_eraseblock (struct jffs2_sb_info *c, struct jffs2_eraseblo
 #endif
 
         if (jffs2_sum_active()) {
-                sm = kmalloc(sizeof(struct jffs2_sum_marker), GFP_KERNEL);
-                if (!sm) {
-                        return -ENOMEM;
-                }
+                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;
+                                }
+                        }
 
-                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);
+                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);
                 }
-
-                kfree(sm);
         }
 
         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);
diff --git a/fs/jffs2/summary.c b/fs/jffs2/summary.c
index 48293c197f13..82a3706c54d8 100644
--- a/fs/jffs2/summary.c
+++ b/fs/jffs2/summary.c
@@ -318,7 +318,6 @@ static int jffs2_sum_process_sum_data(struct jffs2_sb_info *c, struct jffs2_eras
                                 raw = jffs2_alloc_raw_node_ref();
                                 if (!raw) {
                                         JFFS2_NOTICE("allocation of node reference failed\n");
-                                        kfree(summary);
                                         return -ENOMEM;
                                 }
 
@@ -326,7 +325,6 @@ static int jffs2_sum_process_sum_data(struct jffs2_sb_info *c, struct jffs2_eras
                                 if (!ic) {
                                         JFFS2_NOTICE("scan_make_ino_cache failed\n");
                                         jffs2_free_raw_node_ref(raw);
-                                        kfree(summary);
                                         return -ENOMEM;
                                 }
 
@@ -358,10 +356,8 @@ static int jffs2_sum_process_sum_data(struct jffs2_sb_info *c, struct jffs2_eras
                                                         jeb->offset + je32_to_cpu(spd->offset));
 
                                 fd = jffs2_alloc_full_dirent(spd->nsize+1);
-                                if (!fd) {
-                                        kfree(summary);
+                                if (!fd)
                                         return -ENOMEM;
-                                }
 
                                 memcpy(&fd->name, spd->name, spd->nsize);
                                 fd->name[spd->nsize] = 0;
@@ -370,7 +366,6 @@ static int jffs2_sum_process_sum_data(struct jffs2_sb_info *c, struct jffs2_eras
                                 if (!raw) {
                                         jffs2_free_full_dirent(fd);
                                         JFFS2_NOTICE("allocation of node reference failed\n");
-                                        kfree(summary);
                                         return -ENOMEM;
                                 }
 
@@ -378,7 +373,6 @@ static int jffs2_sum_process_sum_data(struct jffs2_sb_info *c, struct jffs2_eras
                                 if (!ic) {
                                         jffs2_free_full_dirent(fd);
                                         jffs2_free_raw_node_ref(raw);
-                                        kfree(summary);
                                         return -ENOMEM;
                                 }
 
@@ -411,45 +405,28 @@ static int jffs2_sum_process_sum_data(struct jffs2_sb_info *c, struct jffs2_eras
 
                         default : {
                                 JFFS2_WARNING("Unsupported node type found in summary! Exiting...");
-                                kfree(summary);
                                 return -EIO;
                         }
                 }
         }
 
-        kfree(summary);
         return 0;
 }
 
 /* Process the summary node - called from jffs2_scan_eraseblock() */
-
 int jffs2_sum_scan_sumnode(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
-                                uint32_t ofs, uint32_t *pseudo_random)
+                           struct jffs2_raw_summary *summary, uint32_t sumsize,
+                           uint32_t *pseudo_random)
 {
         struct jffs2_unknown_node crcnode;
         struct jffs2_raw_node_ref *cache_ref;
-        struct jffs2_raw_summary *summary;
-        int ret, sumsize;
+        int ret, ofs;
         uint32_t crc;
 
-        sumsize = c->sector_size - ofs;
-        ofs += jeb->offset;
+        ofs = jeb->offset + c->sector_size - sumsize;
 
         dbg_summary("summary found for 0x%08x at 0x%08x (0x%x bytes)\n",
-                                jeb->offset, ofs, sumsize);
-
-        summary = kmalloc(sumsize, GFP_KERNEL);
-
-        if (!summary) {
-                return -ENOMEM;
-        }
-
-        ret = jffs2_fill_scan_buf(c, (unsigned char *)summary, ofs, sumsize);
-
-        if (ret) {
-                kfree(summary);
-                return ret;
-        }
+                    jeb->offset, ofs, sumsize);
 
         /* OK, now check for node validity and CRC */
         crcnode.magic = cpu_to_je16(JFFS2_MAGIC_BITMASK);
@@ -499,7 +476,6 @@ int jffs2_sum_scan_sumnode(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb
 
                         if (!marker_ref) {
                                 JFFS2_NOTICE("Failed to allocate node ref for clean marker\n");
-                                kfree(summary);
                                 return -ENOMEM;
                         }
 
diff --git a/fs/jffs2/summary.h b/fs/jffs2/summary.h
index b7a678be1709..afff4bd551a1 100644
--- a/fs/jffs2/summary.h
+++ b/fs/jffs2/summary.h
@@ -160,7 +160,8 @@ int jffs2_sum_add_padding_mem(struct jffs2_summary *s, uint32_t size);
 int jffs2_sum_add_inode_mem(struct jffs2_summary *s, struct jffs2_raw_inode *ri, uint32_t ofs);
 int jffs2_sum_add_dirent_mem(struct jffs2_summary *s, struct jffs2_raw_dirent *rd, uint32_t ofs);
 int jffs2_sum_scan_sumnode(struct jffs2_sb_info *c, struct jffs2_eraseblock *jeb,
-                        uint32_t ofs, uint32_t *pseudo_random);
+                           struct jffs2_raw_summary *summary, uint32_t sumlen,
+                           uint32_t *pseudo_random);
 
 #else                           /* SUMMARY DISABLED */