libext2fs: factor out I/O buffer allocation

Create a new function, io_channel_alloc_buf() which allocates I/O
buffers with appropriate alignment if we are using direct I/O.  The
original code was sometimes using a larger alignment factor than
necessary, and would always request an aligned memory buffer even when
it was not necessary since the block device was not opened with
O_DIRECT.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 17 insertions, 0 deletions

diff --git a/lib/ext2fs/io_manager.c b/lib/ext2fs/io_manager.c
index 25df59ec..34e48592 100644
--- a/lib/ext2fs/io_manager.c
+++ b/lib/ext2fs/io_manager.c
@@ -111,3 +111,20 @@ errcode_t io_channel_discard(io_channel channel, unsigned long long block,
 
 	return EXT2_ET_UNIMPLEMENTED;
 }
+
+errcode_t io_channel_alloc_buf(io_channel io, int count, void *ptr)
+{
+	size_t	size;
+
+	if (count == 0)
+		size = io->block_size;
+	else if (count > 0)
+		size = io->block_size * count;
+	else
+		size = -count;
+
+	if (io->align)
+		return ext2fs_get_memalign(size, io->align, ptr);
+	else
+		return ext2fs_get_mem(size, ptr);
+}