[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>

1 files changed, 6 insertions, 30 deletions

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;
                         }