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[JFFS2] Optimise reading of eraseblock summary nodes
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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>
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David Woodhouse committed May 20, 2006
1 parent 6c8b44a commit 9641b78
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Showing 3 changed files with 64 additions and 49 deletions.
74 changes: 56 additions & 18 deletions fs/jffs2/scan.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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);
Expand Down
36 changes: 6 additions & 30 deletions fs/jffs2/summary.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -318,15 +318,13 @@ 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;
}

ic = jffs2_scan_make_ino_cache(c, ino);
if (!ic) {
JFFS2_NOTICE("scan_make_ino_cache failed\n");
jffs2_free_raw_node_ref(raw);
kfree(summary);
return -ENOMEM;
}

Expand Down Expand Up @@ -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;
Expand All @@ -370,15 +366,13 @@ 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;
}

ic = jffs2_scan_make_ino_cache(c, je32_to_cpu(spd->pino));
if (!ic) {
jffs2_free_full_dirent(fd);
jffs2_free_raw_node_ref(raw);
kfree(summary);
return -ENOMEM;
}

Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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;
}

Expand Down
3 changes: 2 additions & 1 deletion fs/jffs2/summary.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 */

Expand Down

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