Commit e5174baa authored by OGAWA Hirofumi's avatar OGAWA Hirofumi Committed by Linus Torvalds
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[PATCH] fat: support ->direct_IO() 



This patch add to support of ->direct_IO() for mostly read.

The user of this seems to want to use for streaming read.  So, current direct
I/O has limitation, it can only overwrite.  (For write operation, mainly we
need to handle the hole etc..)

Signed-off-by: default avatarOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 7c709d00

fs/fat/cache.c

+11 −3
Original line number Diff line number Diff line
@@ -295,7 +295,8 @@ static int fat_bmap_cluster(struct inode *inode, int cluster) 
	return dclus;

}



int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys)

int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,

	     unsigned long *mapped_blocks)

{

	struct super_block *sb = inode->i_sb;

	struct msdos_sb_info *sbi = MSDOS_SB(sb);
@@ -303,9 +304,12 @@ int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys) 
	int cluster, offset;



	*phys = 0;

	*mapped_blocks = 0;

	if ((sbi->fat_bits != 32) && (inode->i_ino == MSDOS_ROOT_INO)) {

		if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits))

		if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {

			*phys = sector + sbi->dir_start;

			*mapped_blocks = 1;

		}

		return 0;

	}

	last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
@@ -318,7 +322,11 @@ int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys) 
	cluster = fat_bmap_cluster(inode, cluster);

	if (cluster < 0)

		return cluster;

	else if (cluster)

	else if (cluster) {

		*phys = fat_clus_to_blknr(sbi, cluster) + offset;

		*mapped_blocks = sbi->sec_per_clus - offset;

		if (*mapped_blocks > last_block - sector)

			*mapped_blocks = last_block - sector;

	}

	return 0;

}

fs/fat/dir.c

+3 −3
Original line number Diff line number Diff line
@@ -68,8 +68,8 @@ static int fat__get_entry(struct inode *dir, loff_t *pos, 
{

	struct super_block *sb = dir->i_sb;

	sector_t phys, iblock;

	int offset;

	int err;

	unsigned long mapped_blocks;

	int err, offset;



next:

	if (*bh)
@@ -77,7 +77,7 @@ next: 


	*bh = NULL;

	iblock = *pos >> sb->s_blocksize_bits;

	err = fat_bmap(dir, iblock, &phys);

	err = fat_bmap(dir, iblock, &phys, &mapped_blocks);

	if (err || !phys)

		return -1;	/* beyond EOF or error */

fs/fat/inode.c

+73 −9
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <linux/mount.h>

#include <linux/vfs.h>

#include <linux/parser.h>

#include <linux/uio.h>

#include <asm/unaligned.h>



#ifndef CONFIG_FAT_DEFAULT_IOCHARSET
@@ -49,43 +50,77 @@ static int fat_add_cluster(struct inode *inode) 
	return err;

}



static int fat_get_block(struct inode *inode, sector_t iblock,

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;

	struct msdos_sb_info *sbi = MSDOS_SB(sb);

	sector_t phys;

	int err;

	unsigned long mapped_blocks;

	int err, offset;



	err = fat_bmap(inode, iblock, &phys);

	err = fat_bmap(inode, iblock, &phys, &mapped_blocks);

	if (err)

		return err;

	if (phys) {

		map_bh(bh_result, sb, phys);

		*max_blocks = min(mapped_blocks, *max_blocks);

		return 0;

	}

	if (!create)

		return 0;



	if (iblock != MSDOS_I(inode)->mmu_private >> sb->s_blocksize_bits) {

		fat_fs_panic(sb, "corrupted file size (i_pos %lld, %lld)",

			     MSDOS_I(inode)->i_pos, MSDOS_I(inode)->mmu_private);

		return -EIO;

	}

	if (!((unsigned long)iblock & (MSDOS_SB(sb)->sec_per_clus - 1))) {



	offset = (unsigned long)iblock & (sbi->sec_per_clus - 1);

	if (!offset) {

		/* TODO: multiple cluster allocation would be desirable. */

		err = fat_add_cluster(inode);

		if (err)

			return err;

	}

	MSDOS_I(inode)->mmu_private += sb->s_blocksize;

	err = fat_bmap(inode, iblock, &phys);

	/* available blocks on this cluster */

	mapped_blocks = sbi->sec_per_clus - offset;



	*max_blocks = min(mapped_blocks, *max_blocks);

	MSDOS_I(inode)->mmu_private += *max_blocks << sb->s_blocksize_bits;



	err = fat_bmap(inode, iblock, &phys, &mapped_blocks);

	if (err)

		return err;

	if (!phys)

		BUG();

	BUG_ON(!phys);

	BUG_ON(*max_blocks != mapped_blocks);

	set_buffer_new(bh_result);

	map_bh(bh_result, sb, phys);

	return 0;

}



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;



	err = __fat_get_blocks(inode, iblock, &max_blocks, bh_result, create);

	if (err)

		return err;

	bh_result->b_size = max_blocks << sb->s_blocksize_bits;

	return 0;

}



static int fat_get_block(struct inode *inode, sector_t iblock,

			 struct buffer_head *bh_result, int create)

{

	unsigned long max_blocks = 1;

	return __fat_get_blocks(inode, iblock, &max_blocks, bh_result, create);

}



static int fat_writepage(struct page *page, struct writeback_control *wbc)

{

	return block_write_full_page(page, fat_get_block, wbc);
@@ -128,6 +163,34 @@ static int fat_commit_write(struct file *file, struct page *page, 
	return err;

}



static ssize_t fat_direct_IO(int rw, struct kiocb *iocb,

			     const struct iovec *iov,

			     loff_t offset, unsigned long nr_segs)

{

	struct file *file = iocb->ki_filp;

	struct inode *inode = file->f_mapping->host;



	if (rw == WRITE) {

		/*

		 * FIXME: blockdev_direct_IO() doesn't use ->prepare_write(),

		 * so we need to update the ->mmu_private to block boundary.

		 *

		 * But we must fill the remaining area or hole by nul for

		 * updating ->mmu_private.

		 */

		loff_t size = offset + iov_length(iov, nr_segs);

		if (MSDOS_I(inode)->mmu_private < size)

			return -EINVAL;

	}



	/*

	 * FAT need to use the DIO_LOCKING for avoiding the race

	 * condition of fat_get_block() and ->truncate().

	 */

	return blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,

				  offset, nr_segs, fat_get_blocks, NULL);

}



static sector_t _fat_bmap(struct address_space *mapping, sector_t block)

{

	return generic_block_bmap(mapping, block, fat_get_block);
@@ -141,6 +204,7 @@ static struct address_space_operations fat_aops = { 
	.sync_page	= block_sync_page,

	.prepare_write	= fat_prepare_write,

	.commit_write	= fat_commit_write,

	.direct_IO	= fat_direct_IO,

	.bmap		= _fat_bmap

};

include/linux/msdos_fs.h

+2 −1
Original line number Diff line number Diff line
@@ -329,7 +329,8 @@ static inline void fatwchar_to16(__u8 *dst, const wchar_t *src, size_t len) 
extern void fat_cache_inval_inode(struct inode *inode);

extern int fat_get_cluster(struct inode *inode, int cluster,

			   int *fclus, int *dclus);

extern int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys);

extern int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,

		    unsigned long *mapped_blocks);



/* fat/dir.c */

extern struct file_operations fat_dir_operations;

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