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Btrfs: Add O_DIRECT read and write (writes == buffered + cache flush)

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This adds basic O_DIRECT read and write support.  In the write case, we
just do a normal buffered write followed by a cache flush.  O_DIRECT +
O_SYNC are required to trigger metadata syncs.

In the read case, there is a basic btrfs_get_block call for use by
the generic O_DIRECT code.  This does honor multi-volume mapping rules
but it skips all checksumming.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Chris Mason
2008-04-10 10:23:21 -04:00
parent 85d824c4a4
commit 1643298592
2 changed files with 75 additions and 2 deletions
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66
fs/btrfs/inode.c
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@@ -2265,6 +2265,70 @@ out:
return em;
}
static int btrfs_get_block(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create)
{
struct extent_map *em;
u64 start = (u64)iblock << inode->i_blkbits;
struct btrfs_multi_bio *multi = NULL;
struct btrfs_root *root = BTRFS_I(inode)->root;
u64 len;
u64 logical;
u64 map_length;
int ret = 0;
em = btrfs_get_extent(inode, NULL, 0, start, bh_result->b_size, 0);
if (!em || IS_ERR(em))
goto out;
if (em->start > start || em->start + em->len <= start)
goto out;
if (em->block_start == EXTENT_MAP_INLINE) {
ret = -EINVAL;
goto out;
}
if (em->block_start == EXTENT_MAP_HOLE ||
em->block_start == EXTENT_MAP_DELALLOC) {
goto out;
}
len = em->start + em->len - start;
len = min_t(u64, len, INT_LIMIT(typeof(bh_result->b_size)));
logical = start - em->start;
logical = em->block_start + logical;
map_length = len;
ret = btrfs_map_block(&root->fs_info->mapping_tree, READ,
logical, &map_length, &multi, 0);
BUG_ON(ret);
bh_result->b_blocknr = multi->stripes[0].physical >> inode->i_blkbits;
bh_result->b_size = min(map_length, len);
bh_result->b_bdev = multi->stripes[0].dev->bdev;
set_buffer_mapped(bh_result);
kfree(multi);
out:
free_extent_map(em);
return ret;
}
static ssize_t btrfs_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)
return -EINVAL;
return blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
offset, nr_segs, btrfs_get_block, NULL);
}
static sector_t btrfs_bmap(struct address_space *mapping, sector_t iblock)
{
return extent_bmap(mapping, iblock, btrfs_get_extent);
@@ -3136,6 +3200,7 @@ out_fail:
btrfs_throttle(root);
return err;
}
static int btrfs_permission(struct inode *inode, int mask,
struct nameidata *nd)
{
@@ -3193,6 +3258,7 @@ static struct address_space_operations btrfs_aops = {
.readpages = btrfs_readpages,
.sync_page = block_sync_page,
.bmap = btrfs_bmap,
.direct_IO = btrfs_direct_IO,
.invalidatepage = btrfs_invalidatepage,
.releasepage = btrfs_releasepage,
.set_page_dirty = __set_page_dirty_nobuffers,