[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/inode.c b/fs/fat/inode.c
index 932c8d6..e7f4aa7 100644
--- 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 @@
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 @@
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 @@
.sync_page = block_sync_page,
.prepare_write = fat_prepare_write,
.commit_write = fat_commit_write,
+ .direct_IO = fat_direct_IO,
.bmap = _fat_bmap
};