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Subject[PATCH] ext3 getblocks() support for read
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Hi,

Here is the patch to support ext3 getblocks() for non allocation
cases. (for reads & re-writes). This is useful with DIO reads,
DIO re-writes and to go with Christoph's getblocks() for readpages()
work.

Mingming is working on adding multiblock allocation support using
reservation (which can be incrementally added later).

Comments ?

Thanks,
Badari


Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
--- linux-2.6.15-rc2/fs/ext3/inode.c 2005-11-19 19:25:03.000000000 -0800
+++ linux-2.6.15-rc2.new/fs/ext3/inode.c 2005-11-30 08:16:36.000000000 -0800
@@ -329,8 +329,9 @@ static int ext3_block_to_path(struct ino
} else {
ext3_warning (inode->i_sb, "ext3_block_to_path", "block > big");
}
- if (boundary)
- *boundary = (i_block & (ptrs - 1)) == (final - 1);
+ if (boundary) {
+ *boundary = final - 1 - (i_block & (ptrs - 1));
+ }
return n;
}

@@ -672,8 +673,9 @@ err_out:
*/

static int
-ext3_get_block_handle(handle_t *handle, struct inode *inode, sector_t iblock,
- struct buffer_head *bh_result, int create, int extend_disksize)
+ext3_get_blocks_handle(handle_t *handle, struct inode *inode, sector_t iblock,
+ int max_blocks,struct buffer_head *bh_result, int create,
+ int extend_disksize)
{
int err = -EIO;
int offsets[4];
@@ -681,9 +683,10 @@ ext3_get_block_handle(handle_t *handle,
Indirect *partial;
unsigned long goal;
int left;
- int boundary = 0;
- const int depth = ext3_block_to_path(inode, iblock, offsets, &boundary);
+ int blks_boundary = 0;
+ const int depth = ext3_block_to_path(inode, iblock, offsets, &blks_boundary);
struct ext3_inode_info *ei = EXT3_I(inode);
+ int count = 1;

J_ASSERT(handle != NULL || create == 0);

@@ -694,7 +697,18 @@ ext3_get_block_handle(handle_t *handle,

/* Simplest case - block found, no allocation needed */
if (!partial) {
+ unsigned long first_block = le32_to_cpu(chain[depth-1].key);
+
clear_buffer_new(bh_result);
+
+ /*
+ * Find all the contiguous blocks and return at once.
+ */
+ while (count < max_blocks && count <= blks_boundary &&
+ (le32_to_cpu(*(chain[depth-1].p+count)) ==
+ (first_block + count))) {
+ count++;
+ }
goto got_it;
}

@@ -772,8 +786,9 @@ ext3_get_block_handle(handle_t *handle,
set_buffer_new(bh_result);
got_it:
map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
- if (boundary)
+ if (blks_boundary == 0)
set_buffer_boundary(bh_result);
+ err = count;
/* Clean up and exit */
partial = chain + depth - 1; /* the whole chain */
cleanup:
@@ -787,6 +802,19 @@ out:
return err;
}

+static int
+ext3_get_block_handle(handle_t *handle, struct inode *inode, sector_t iblock,
+ struct buffer_head *bh_result, int create, int extend_disksize)
+{
+ int ret;
+ ret = ext3_get_blocks_handle(handle, inode, iblock, 1, bh_result,
+ create, extend_disksize);
+ if (ret > 0)
+ ret = 0;
+
+ return ret;
+}
+
static int ext3_get_block(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create)
{
@@ -842,9 +870,13 @@ ext3_direct_io_get_blocks(struct inode *

get_block:
if (ret == 0)
- ret = ext3_get_block_handle(handle, inode, iblock,
- bh_result, create, 0);
- bh_result->b_size = (1 << inode->i_blkbits);
+ ret = ext3_get_blocks_handle(handle, inode, iblock,
+ max_blocks, bh_result, create, 0);
+
+ if (ret > 0)
+ bh_result->b_size = (ret << inode->i_blkbits);
+ else
+ bh_result->b_size = (1 << inode->i_blkbits);
return ret;
}
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