On Mon, 2006-03-06 at 14:37 -0800, Andrew Morton wrote:
> Badari Pulavarty <[email protected]> wrote:
> >
> > Instead of passing validity of block mapping, do_mpage_readpage()
> > can figure it out using buffer_mapped(). This will reduce one
> > un-needed argument passing.
>
> Is buffer_mapped() the correct flag to use? Remember that get_block() can
> validly return a !buffer_mapped() bh over a file hole.
>
> Either way, there should be a comment in there explaining the protocol,
> please.
>
Here is the version with comments.
Thanks,
Badari
Instead of passing validity of block mapping, do_mpage_readpage()
can figure it out using buffer_mapped(). This will reduce one
un-needed argument passing.
Signed-off-by: Badari Pulavarty <[email protected]>
Index: linux-2.6.16-rc5-mm2/fs/mpage.c
===================================================================
--- linux-2.6.16-rc5-mm2.orig/fs/mpage.c 2006-03-03 13:46:22.000000000 -0800
+++ linux-2.6.16-rc5-mm2/fs/mpage.c 2006-03-06 17:13:02.000000000 -0800
@@ -163,10 +163,19 @@ map_buffer_to_page(struct page *page, st
} while (page_bh != head);
}
+/*
+ * This is the worker routine which does all the work of mapping the
+ * disk blocks and constructs largest possible bios, submits them for
+ * IO if the blocks are not contiguous on the disk.
+ *
+ * Its important to note that, we pass buffer_head back and forth and
+ * use buffer_mapped() flag to represent the validity of disk mapping
+ * and to decide when to do next get_block() call.
+ */
static struct bio *
do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
sector_t *last_block_in_bio, struct buffer_head *map_bh,
- unsigned long *first_logical_block, int *map_valid,
+ unsigned long *first_logical_block,
get_block_t get_block)
{
struct inode *inode = page->mapping->host;
@@ -199,14 +208,14 @@ do_mpage_readpage(struct bio *bio, struc
* Map blocks using the result from the previous get_blocks call first.
*/
nblocks = map_bh->b_size >> blkbits;
- if (*map_valid && block_in_file > *first_logical_block &&
+ if (buffer_mapped(map_bh) && block_in_file > *first_logical_block &&
block_in_file < (*first_logical_block + nblocks)) {
unsigned map_offset = block_in_file - *first_logical_block;
unsigned last = nblocks - map_offset;
for (relative_block = 0; ; relative_block++) {
if (relative_block == last) {
- *map_valid = 0;
+ clear_buffer_mapped(map_bh);
break;
}
if (page_block == blocks_per_page)
@@ -232,7 +241,6 @@ do_mpage_readpage(struct bio *bio, struc
if (get_block(inode, block_in_file, map_bh, 0))
goto confused;
*first_logical_block = block_in_file;
- *map_valid = 1;
}
if (!buffer_mapped(map_bh)) {
@@ -241,7 +249,7 @@ do_mpage_readpage(struct bio *bio, struc
first_hole = page_block;
page_block++;
block_in_file++;
- *map_valid = 0;
+ clear_buffer_mapped(map_bh);
continue;
}
@@ -265,7 +273,7 @@ do_mpage_readpage(struct bio *bio, struc
nblocks = map_bh->b_size >> blkbits;
for (relative_block = 0; ; relative_block++) {
if (relative_block == nblocks) {
- *map_valid = 0;
+ clear_buffer_mapped(map_bh);
break;
} else if (page_block == blocks_per_page)
break;
@@ -385,8 +393,8 @@ mpage_readpages(struct address_space *ma
struct pagevec lru_pvec;
struct buffer_head map_bh;
unsigned long first_logical_block = 0;
- int map_valid = 0;
+ clear_buffer_mapped(&map_bh);
pagevec_init(&lru_pvec, 0);
for (page_idx = 0; page_idx < nr_pages; page_idx++) {
struct page *page = list_entry(pages->prev, struct page, lru);
@@ -399,7 +407,7 @@ mpage_readpages(struct address_space *ma
nr_pages - page_idx,
&last_block_in_bio, &map_bh,
&first_logical_block,
- &map_valid, get_block);
+ get_block);
if (!pagevec_add(&lru_pvec, page))
__pagevec_lru_add(&lru_pvec);
} else {
@@ -423,12 +431,10 @@ int mpage_readpage(struct page *page, ge
sector_t last_block_in_bio = 0;
struct buffer_head map_bh;
unsigned long first_logical_block = 0;
- int map_valid = 0;
-
+ clear_buffer_mapped(&map_bh);
bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
- &map_bh, &first_logical_block, &map_valid,
- get_block);
+ &map_bh, &first_logical_block, get_block);
if (bio)
mpage_bio_submit(READ, bio);
return 0;
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