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authorChris Mason <chris.mason@oracle.com>2009-03-31 13:27:11 -0400
committerChris Mason <chris.mason@oracle.com>2009-03-31 14:27:58 -0400
commit5a3f23d515a2ebf0c750db80579ca57b28cbce6d (patch)
treee0ffb43dd35f1c3def9a74ec7a6f4470902c9761 /fs/btrfs/file.c
parent1a81af4d1d9c60d4313309f937a1fc5567205a87 (diff)
Btrfs: add extra flushing for renames and truncates
Renames and truncates are both common ways to replace old data with new data. The filesystem can make an effort to make sure the new data is on disk before actually replacing the old data. This is especially important for rename, which many application use as though it were atomic for both the data and the metadata involved. The current btrfs code will happily replace a file that is fully on disk with one that was just created and still has pending IO. If we crash after transaction commit but before the IO is done, we'll end up replacing a good file with a zero length file. The solution used here is to create a list of inodes that need special ordering and force them to disk before the commit is done. This is similar to the ext3 style data=ordering, except it is only done on selected files. Btrfs is able to get away with this because it does not wait on commits very often, even for fsync (which use a sub-commit). For renames, we order the file when it wasn't already on disk and when it is replacing an existing file. Larger files are sent to filemap_flush right away (before the transaction handle is opened). For truncates, we order if the file goes from non-zero size down to zero size. This is a little different, because at the time of the truncate the file has no dirty bytes to order. But, we flag the inode so that it is added to the ordered list on close (via release method). We also immediately add it to the ordered list of the current transaction so that we can try to flush down any writes the application sneaks in before commit. Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/file.c')
-rw-r--r--fs/btrfs/file.c26
1 files changed, 26 insertions, 0 deletions
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 32d10a61761..9c9fb46ccd0 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1161,6 +1161,20 @@ out_nolock:
page_cache_release(pinned[1]);
*ppos = pos;
+ /*
+ * we want to make sure fsync finds this change
+ * but we haven't joined a transaction running right now.
+ *
+ * Later on, someone is sure to update the inode and get the
+ * real transid recorded.
+ *
+ * We set last_trans now to the fs_info generation + 1,
+ * this will either be one more than the running transaction
+ * or the generation used for the next transaction if there isn't
+ * one running right now.
+ */
+ BTRFS_I(inode)->last_trans = root->fs_info->generation + 1;
+
if (num_written > 0 && will_write) {
struct btrfs_trans_handle *trans;
@@ -1194,6 +1208,18 @@ out_nolock:
int btrfs_release_file(struct inode *inode, struct file *filp)
{
+ /*
+ * ordered_data_close is set by settattr when we are about to truncate
+ * a file from a non-zero size to a zero size. This tries to
+ * flush down new bytes that may have been written if the
+ * application were using truncate to replace a file in place.
+ */
+ if (BTRFS_I(inode)->ordered_data_close) {
+ BTRFS_I(inode)->ordered_data_close = 0;
+ btrfs_add_ordered_operation(NULL, BTRFS_I(inode)->root, inode);
+ if (inode->i_size > BTRFS_ORDERED_OPERATIONS_FLUSH_LIMIT)
+ filemap_flush(inode->i_mapping);
+ }
if (filp->private_data)
btrfs_ioctl_trans_end(filp);
return 0;