[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: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 11 insertions, 3 deletions

diff --git a/fs/fat/cache.c b/fs/fat/cache.c
index 77c24fcf712a..1acc941245fb 100644
--- a/fs/fat/cache.c
+++ b/fs/fat/cache.c
@@ -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;
 }