[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>

diff --git a/fs/fat/cache.c b/fs/fat/cache.c
index 77c24fcf712aefdc626781eee7a5bcbb10c62493..1acc941245fb4a4c751c972684202b19d0f2208a 100644 (file)
--- 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;
 }

diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 4ce77475aed3992c3c372888fe4ab84c1a624b22..eef1b81aa294d8a8f82686030edea5ca006ce320 100644 (file)
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -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 */
 

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 932c8d6d1f5477a504c496810b6427b37ce0777f..e7f4aa7fc6864be095def4db3ac8078f7f218052 100644 (file)
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -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,
-                        struct buffer_head *bh_result, int create)
+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
 };
 

diff --git a/include/linux/msdos_fs.h b/include/linux/msdos_fs.h
index 941da5c016a01e1434d3291fe1ec466c16adbb45..e933e2a355adcea8331913ca5aec0bc6cdf9d3ce 100644 (file)
--- a/include/linux/msdos_fs.h
+++ b/include/linux/msdos_fs.h
@@ -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;