Re: [RFC][PATCH] map multiple blocks at a time in mpage_readpages()

From: Badari Pulavarty
Date: Tue Feb 14 2006 - 17:50:11 EST

On Tue, 2006-02-14 at 20:27 +0100, christoph wrote:
> On Tue, Feb 14, 2006 at 09:49:07AM -0800, Badari Pulavarty wrote:
> > Hi,
> >
> > I re-did the support for mpage_readpages() to map multiple blocks
> > at a time (basically, get_blocks()). Instead of adding new
> > get_blocks() and pass it around, I use "bh->b_size" to indicate
> > how much of disk mapping we are interested in to get_block().
> >
> > This way no changes existing interfaces and no new routines need.
> > Filesystem can choose to ignore the passed in "bh->b_size" value
> > and map one block at a time (ext2, reiser3, etc..)
>
> Hmm. Given that we only use buffer_heads for page-cache backed I/O
> bh->b_size should always be set properly and this would be fine.
>
> If we could completely get rid of ->get_blocks that be a nice cleanup
> in all the fs drivers.

Here is the patch to remove ->get_blocks from all fs.
Unfortunately, some filesystems (ext3, reiser3) does extra stuff
in ->getblocks() for DIO. So I can't quite get rid of them :(
But in general, it cleans up a lot.

Thanks,
Badari



Index: linux-2.6.16-rc3/fs/direct-io.c
===================================================================
--- linux-2.6.16-rc3.orig/fs/direct-io.c 2006-02-12 16:27:25.000000000 -0800
+++ linux-2.6.16-rc3/fs/direct-io.c 2006-02-14 14:32:11.000000000 -0800
@@ -86,12 +86,12 @@ struct dio {
unsigned first_block_in_page; /* doesn't change, Used only once */
int boundary; /* prev block is at a boundary */
int reap_counter; /* rate limit reaping */
- get_blocks_t *get_blocks; /* block mapping function */
+ get_block_t *get_block; /* block mapping function */
dio_iodone_t *end_io; /* IO completion function */
sector_t final_block_in_bio; /* current final block in bio + 1 */
sector_t next_block_for_io; /* next block to be put under IO,
in dio_blocks units */
- struct buffer_head map_bh; /* last get_blocks() result */
+ struct buffer_head map_bh; /* last get_block() result */

/*
* Deferred addition of a page to the dio. These variables are
@@ -210,9 +210,9 @@ static struct page *dio_get_page(struct

/*
* Called when all DIO BIO I/O has been completed - let the filesystem
- * know, if it registered an interest earlier via get_blocks. Pass the
+ * know, if it registered an interest earlier via get_block. Pass the
* private field of the map buffer_head so that filesystems can use it
- * to hold additional state between get_blocks calls and dio_complete.
+ * to hold additional state between get_block calls and dio_complete.
*/
static void dio_complete(struct dio *dio, loff_t offset, ssize_t bytes)
{
@@ -488,7 +488,7 @@ static int dio_bio_reap(struct dio *dio)
* The fs is allowed to map lots of blocks at once. If it wants to do that,
* it uses the passed inode-relative block number as the file offset, as usual.
*
- * get_blocks() is passed the number of i_blkbits-sized blocks which direct_io
+ * get_block() is passed the number of i_blkbits-sized blocks which direct_io
* has remaining to do. The fs should not map more than this number of blocks.
*
* If the fs has mapped a lot of blocks, it should populate bh->b_size to
@@ -501,7 +501,7 @@ static int dio_bio_reap(struct dio *dio)
* In the case of filesystem holes: the fs may return an arbitrarily-large
* hole by returning an appropriate value in b_size and by clearing
* buffer_mapped(). However the direct-io code will only process holes one
- * block at a time - it will repeatedly call get_blocks() as it walks the hole.
+ * block at a time - it will repeatedly call get_block() as it walks the hole.
*/
static int get_more_blocks(struct dio *dio)
{
@@ -543,7 +543,8 @@ static int get_more_blocks(struct dio *d
* at a higher level for inside-i_size block-instantiating
* writes.
*/
- ret = (*dio->get_blocks)(dio->inode, fs_startblk, fs_count,
+ map_bh->b_size = fs_count << dio->blkbits;
+ ret = (*dio->get_block)(dio->inode, fs_startblk,
map_bh, create);
}
return ret;
@@ -778,11 +779,11 @@ static void dio_zero_block(struct dio *d
* happily perform page-sized but 512-byte aligned IOs. It is important that
* blockdev IO be able to have fine alignment and large sizes.
*
- * So what we do is to permit the ->get_blocks function to populate bh.b_size
+ * So what we do is to permit the ->get_block function to populate bh.b_size
* with the size of IO which is permitted at this offset and this i_blkbits.
*
* For best results, the blockdev should be set up with 512-byte i_blkbits and
- * it should set b_size to PAGE_SIZE or more inside get_blocks(). This gives
+ * it should set b_size to PAGE_SIZE or more inside get_block(). This gives
* fine alignment but still allows this function to work in PAGE_SIZE units.
*/
static int do_direct_IO(struct dio *dio)
@@ -942,7 +943,7 @@ out:
static ssize_t
direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
const struct iovec *iov, loff_t offset, unsigned long nr_segs,
- unsigned blkbits, get_blocks_t get_blocks, dio_iodone_t end_io,
+ unsigned blkbits, get_block_t get_block, dio_iodone_t end_io,
struct dio *dio)
{
unsigned long user_addr;
@@ -964,7 +965,7 @@ direct_io_worker(int rw, struct kiocb *i

dio->boundary = 0;
dio->reap_counter = 0;
- dio->get_blocks = get_blocks;
+ dio->get_block = get_block;
dio->end_io = end_io;
dio->map_bh.b_private = NULL;
dio->final_block_in_bio = -1;
@@ -1170,7 +1171,7 @@ direct_io_worker(int rw, struct kiocb *i
ssize_t
__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
struct block_device *bdev, const struct iovec *iov, loff_t offset,
- unsigned long nr_segs, get_blocks_t get_blocks, dio_iodone_t end_io,
+ unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
int dio_lock_type)
{
int seg;
@@ -1266,7 +1267,7 @@ __blockdev_direct_IO(int rw, struct kioc
(end > i_size_read(inode)));

retval = direct_io_worker(rw, iocb, inode, iov, offset,
- nr_segs, blkbits, get_blocks, end_io, dio);
+ nr_segs, blkbits, get_block, end_io, dio);

if (rw == READ && dio_lock_type == DIO_LOCKING)
reader_with_isem = 0;
Index: linux-2.6.16-rc3/fs/ext2/inode.c
===================================================================
--- linux-2.6.16-rc3.orig/fs/ext2/inode.c 2006-02-12 16:27:25.000000000 -0800
+++ linux-2.6.16-rc3/fs/ext2/inode.c 2006-02-14 14:17:03.000000000 -0800
@@ -667,18 +667,6 @@ static sector_t ext2_bmap(struct address
return generic_block_bmap(mapping,block,ext2_get_block);
}

-static int
-ext2_get_blocks(struct inode *inode, sector_t iblock, unsigned long max_blocks,
- struct buffer_head *bh_result, int create)
-{
- int ret;
-
- ret = ext2_get_block(inode, iblock, bh_result, create);
- if (ret == 0)
- bh_result->b_size = (1 << inode->i_blkbits);
- return ret;
-}
-
static ssize_t
ext2_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
loff_t offset, unsigned long nr_segs)
@@ -687,7 +675,7 @@ ext2_direct_IO(int rw, struct kiocb *ioc
struct inode *inode = file->f_mapping->host;

return blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
- offset, nr_segs, ext2_get_blocks, NULL);
+ offset, nr_segs, ext2_get_block, NULL);
}

static int
Index: linux-2.6.16-rc3/fs/ext3/inode.c
===================================================================
--- linux-2.6.16-rc3.orig/fs/ext3/inode.c 2006-02-12 16:27:25.000000000 -0800
+++ linux-2.6.16-rc3/fs/ext3/inode.c 2006-02-14 14:17:49.000000000 -0800
@@ -806,8 +806,7 @@ static int ext3_get_block(struct inode *

static int
ext3_direct_io_get_blocks(struct inode *inode, sector_t iblock,
- unsigned long max_blocks, struct buffer_head *bh_result,
- int create)
+ struct buffer_head *bh_result, int create)
{
handle_t *handle = journal_current_handle();
int ret = 0;
Index: linux-2.6.16-rc3/fs/fat/inode.c
===================================================================
--- linux-2.6.16-rc3.orig/fs/fat/inode.c 2006-02-12 16:27:25.000000000 -0800
+++ linux-2.6.16-rc3/fs/fat/inode.c 2006-02-14 14:21:21.000000000 -0800
@@ -101,11 +101,11 @@ static int __fat_get_blocks(struct inode
}

static int fat_get_blocks(struct inode *inode, sector_t iblock,
- unsigned long max_blocks,
struct buffer_head *bh_result, int create)
{
struct super_block *sb = inode->i_sb;
int err;
+ unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;

err = __fat_get_blocks(inode, iblock, &max_blocks, bh_result, create);
if (err)
Index: linux-2.6.16-rc3/fs/hfs/inode.c
===================================================================
--- linux-2.6.16-rc3.orig/fs/hfs/inode.c 2006-02-12 16:27:25.000000000 -0800
+++ linux-2.6.16-rc3/fs/hfs/inode.c 2006-02-14 14:24:06.000000000 -0800
@@ -98,17 +98,6 @@ static int hfs_releasepage(struct page *
return res ? try_to_free_buffers(page) : 0;
}

-static int hfs_get_blocks(struct inode *inode, sector_t iblock, unsigned long max_blocks,
- struct buffer_head *bh_result, int create)
-{
- int ret;
-
- ret = hfs_get_block(inode, iblock, bh_result, create);
- if (!ret)
- bh_result->b_size = (1 << inode->i_blkbits);
- return ret;
-}
-
static ssize_t hfs_direct_IO(int rw, struct kiocb *iocb,
const struct iovec *iov, loff_t offset, unsigned long nr_segs)
{
@@ -116,7 +105,7 @@ static ssize_t hfs_direct_IO(int rw, str
struct inode *inode = file->f_dentry->d_inode->i_mapping->host;

return blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
- offset, nr_segs, hfs_get_blocks, NULL);
+ offset, nr_segs, hfs_get_block, NULL);
}

static int hfs_writepages(struct address_space *mapping,
Index: linux-2.6.16-rc3/fs/hfsplus/inode.c
===================================================================
--- linux-2.6.16-rc3.orig/fs/hfsplus/inode.c 2006-02-12 16:27:25.000000000 -0800
+++ linux-2.6.16-rc3/fs/hfsplus/inode.c 2006-02-14 14:13:42.000000000 -0800
@@ -93,17 +93,6 @@ static int hfsplus_releasepage(struct pa
return res ? try_to_free_buffers(page) : 0;
}

-static int hfsplus_get_blocks(struct inode *inode, sector_t iblock, unsigned long max_blocks,
- struct buffer_head *bh_result, int create)
-{
- int ret;
-
- ret = hfsplus_get_block(inode, iblock, bh_result, create);
- if (!ret)
- bh_result->b_size = (1 << inode->i_blkbits);
- return ret;
-}
-
static ssize_t hfsplus_direct_IO(int rw, struct kiocb *iocb,
const struct iovec *iov, loff_t offset, unsigned long nr_segs)
{
@@ -111,7 +100,7 @@ static ssize_t hfsplus_direct_IO(int rw,
struct inode *inode = file->f_dentry->d_inode->i_mapping->host;

return blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
- offset, nr_segs, hfsplus_get_blocks, NULL);
+ offset, nr_segs, hfsplus_get_block, NULL);
}

static int hfsplus_writepages(struct address_space *mapping,
Index: linux-2.6.16-rc3/fs/ocfs2/aops.c
===================================================================
--- linux-2.6.16-rc3.orig/fs/ocfs2/aops.c 2006-02-12 16:27:25.000000000 -0800
+++ linux-2.6.16-rc3/fs/ocfs2/aops.c 2006-02-14 14:26:45.000000000 -0800
@@ -538,7 +538,6 @@ bail:
* fs_count, map_bh, dio->rw == WRITE);
*/
static int ocfs2_direct_IO_get_blocks(struct inode *inode, sector_t iblock,
- unsigned long max_blocks,
struct buffer_head *bh_result, int create)
{
int ret;
@@ -546,6 +545,7 @@ static int ocfs2_direct_IO_get_blocks(st
u64 p_blkno;
int contig_blocks;
unsigned char blocksize_bits;
+ unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;

if (!inode || !bh_result) {
mlog(ML_ERROR, "inode or bh_result is null\n");
Index: linux-2.6.16-rc3/fs/reiserfs/inode.c
===================================================================
--- linux-2.6.16-rc3.orig/fs/reiserfs/inode.c 2006-02-12 16:27:25.000000000 -0800
+++ linux-2.6.16-rc3/fs/reiserfs/inode.c 2006-02-14 14:16:17.000000000 -0800
@@ -466,7 +466,6 @@ static int reiserfs_get_block_create_0(s
direct_IO request. */
static int reiserfs_get_blocks_direct_io(struct inode *inode,
sector_t iblock,
- unsigned long max_blocks,
struct buffer_head *bh_result,
int create)
{
Index: linux-2.6.16-rc3/fs/xfs/linux-2.6/xfs_aops.c
===================================================================
--- linux-2.6.16-rc3.orig/fs/xfs/linux-2.6/xfs_aops.c 2006-02-14 09:43:33.000000000 -0800
+++ linux-2.6.16-rc3/fs/xfs/linux-2.6/xfs_aops.c 2006-02-14 14:31:01.000000000 -0800
@@ -1144,12 +1144,11 @@ STATIC int
linvfs_get_blocks_direct(
struct inode *inode,
sector_t iblock,
- unsigned long max_blocks,
struct buffer_head *bh_result,
int create)
{
- return __linvfs_get_block(inode, iblock, max_blocks, bh_result,
- create, 1, BMAPI_WRITE|BMAPI_DIRECT);
+ return __linvfs_get_block(inode, iblock, bh_result->b_size >> inode->i_blkbits,
+ bh_result, create, 1, BMAPI_WRITE|BMAPI_DIRECT);
}

STATIC void
Index: linux-2.6.16-rc3/include/linux/fs.h
===================================================================
--- linux-2.6.16-rc3.orig/include/linux/fs.h 2006-02-12 16:27:25.000000000 -0800
+++ linux-2.6.16-rc3/include/linux/fs.h 2006-02-14 14:11:54.000000000 -0800
@@ -240,9 +240,6 @@ extern void __init files_init(unsigned l
struct buffer_head;
typedef int (get_block_t)(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create);
-typedef int (get_blocks_t)(struct inode *inode, sector_t iblock,
- unsigned long max_blocks,
- struct buffer_head *bh_result, int create);
typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
ssize_t bytes, void *private);

@@ -1621,7 +1618,7 @@ static inline void do_generic_file_read(

ssize_t __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
struct block_device *bdev, const struct iovec *iov, loff_t offset,
- unsigned long nr_segs, get_blocks_t get_blocks, dio_iodone_t end_io,
+ unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
int lock_type);

enum {
@@ -1632,29 +1629,29 @@ enum {

static inline ssize_t blockdev_direct_IO(int rw, struct kiocb *iocb,
struct inode *inode, struct block_device *bdev, const struct iovec *iov,
- loff_t offset, unsigned long nr_segs, get_blocks_t get_blocks,
+ loff_t offset, unsigned long nr_segs, get_block_t get_block,
dio_iodone_t end_io)
{
return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
- nr_segs, get_blocks, end_io, DIO_LOCKING);
+ nr_segs, get_block, end_io, DIO_LOCKING);
}

static inline ssize_t blockdev_direct_IO_no_locking(int rw, struct kiocb *iocb,
struct inode *inode, struct block_device *bdev, const struct iovec *iov,
- loff_t offset, unsigned long nr_segs, get_blocks_t get_blocks,
+ loff_t offset, unsigned long nr_segs, get_block_t get_block,
dio_iodone_t end_io)
{
return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
- nr_segs, get_blocks, end_io, DIO_NO_LOCKING);
+ nr_segs, get_block, end_io, DIO_NO_LOCKING);
}

static inline ssize_t blockdev_direct_IO_own_locking(int rw, struct kiocb *iocb,
struct inode *inode, struct block_device *bdev, const struct iovec *iov,
- loff_t offset, unsigned long nr_segs, get_blocks_t get_blocks,
+ loff_t offset, unsigned long nr_segs, get_block_t get_block,
dio_iodone_t end_io)
{
return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
- nr_segs, get_blocks, end_io, DIO_OWN_LOCKING);
+ nr_segs, get_block, end_io, DIO_OWN_LOCKING);
}

extern struct file_operations generic_ro_fops;
Index: linux-2.6.16-rc3/fs/block_dev.c
===================================================================
--- linux-2.6.16-rc3.orig/fs/block_dev.c 2006-02-12 16:27:25.000000000 -0800
+++ linux-2.6.16-rc3/fs/block_dev.c 2006-02-14 14:35:01.000000000 -0800
@@ -135,9 +135,10 @@ blkdev_get_block(struct inode *inode, se

static int
blkdev_get_blocks(struct inode *inode, sector_t iblock,
- unsigned long max_blocks, struct buffer_head *bh, int create)
+ struct buffer_head *bh, int create)
{
sector_t end_block = max_block(I_BDEV(inode));
+ unsigned long max_blocks = bh->b_size >> inode->i_blkbits;

if ((iblock + max_blocks) > end_block) {
max_blocks = end_block - iblock;
Index: linux-2.6.16-rc3/fs/jfs/inode.c
===================================================================
--- linux-2.6.16-rc3.orig/fs/jfs/inode.c 2006-02-14 09:43:51.000000000 -0800
+++ linux-2.6.16-rc3/fs/jfs/inode.c 2006-02-14 14:37:28.000000000 -0800
@@ -301,7 +301,7 @@ static ssize_t jfs_direct_IO(int rw, str
struct inode *inode = file->f_mapping->host;

return blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
- offset, nr_segs, jfs_get_blocks, NULL);
+ offset, nr_segs, jfs_get_block, NULL);
}

struct address_space_operations jfs_aops = {