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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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11
fs/btrfs/file.c
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@@ -796,8 +796,6 @@ static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
PAGE_CACHE_SIZE / (sizeof(struct page *)));
pinned[0] = NULL;
pinned[1] = NULL;
if (file->f_flags & O_DIRECT)
return -EINVAL;
pos = *ppos;
start_pos = pos;
@@ -909,6 +907,15 @@ out_nolock:
start_pos, num_written);
if (err < 0)
num_written = err;
} else if (num_written > 0 && (file->f_flags & O_DIRECT)) {
do_sync_mapping_range(inode->i_mapping, start_pos,
start_pos + num_written - 1,
SYNC_FILE_RANGE_WRITE |
SYNC_FILE_RANGE_WAIT_AFTER);
invalidate_mapping_pages(inode->i_mapping,
start_pos >> PAGE_CACHE_SHIFT,
(start_pos + num_written - 1) >> PAGE_CACHE_SHIFT);
}
current->backing_dev_info = NULL;
return num_written ? num_written : err;