libext2fs: fix unix_io's Direct I/O support

The previous Direct I/O support worked on HDD's with 512 byte logical
sector sizes, and on FreeBSD which required 4k aligned memory buffers.
However, it was incomplete and was not correctly working on HDD's with
4k logical sector sizes (aka Advanced Format Disks).

Based on a patch from Alexey Lyashkov <alexey.lyashkov@hpe.com> but
rewritten to work with the latest e2fsprogs and to minimize changes to
make it easier to review.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reported-by: Artem Blagodarenko <artem.blagodarenko@gmail.com>

2 files changed, 70 insertions, 23 deletions

diff --git a/lib/ext2fs/io_manager.c b/lib/ext2fs/io_manager.c
index c395d615f..996c31a14 100644
--- a/lib/ext2fs/io_manager.c
+++ b/lib/ext2fs/io_manager.c
@@ -134,9 +134,11 @@ errcode_t io_channel_alloc_buf(io_channel io, int count, void *ptr)
 	else
 		size = -count;
 
-	if (io->align)
+	if (io->align) {
+		if (io->align > size)
+			size = io->align;
 		return ext2fs_get_memalign(size, io->align, ptr);
-	else
+	} else
 		return ext2fs_get_mem(size, ptr);
 }
 
diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
index 73f5667ec..8965535c3 100644
--- a/lib/ext2fs/unix_io.c
+++ b/lib/ext2fs/unix_io.c
@@ -218,6 +218,8 @@ static errcode_t raw_read_blk(io_channel channel,
 	int		actual = 0;
 	unsigned char	*buf = bufv;
 	ssize_t		really_read = 0;
+	unsigned long long aligned_blk;
+	int		align_size, offset;
 
 	size = (count < 0) ? -count : (ext2_loff_t) count * channel->block_size;
 	mutex_lock(data, STATS_MTX);
@@ -226,7 +228,7 @@ static errcode_t raw_read_blk(io_channel channel,
 	location = ((ext2_loff_t) block * channel->block_size) + data->offset;
 
 	if (data->flags & IO_FLAG_FORCE_BOUNCE) {
-		if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
+		if (ext2fs_llseek(data->dev, location, SEEK_SET) < 0) {
 			retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
 			goto error_out;
 		}
@@ -237,6 +239,7 @@ static errcode_t raw_read_blk(io_channel channel,
 	/* Try an aligned pread */
 	if ((channel->align == 0) ||
 	    (IS_ALIGNED(buf, channel->align) &&
+	     IS_ALIGNED(location, channel->align) &&
 	     IS_ALIGNED(size, channel->align))) {
 		actual = pread64(data->dev, buf, size, location);
 		if (actual == size)
@@ -248,6 +251,7 @@ static errcode_t raw_read_blk(io_channel channel,
 	if ((sizeof(off_t) >= sizeof(ext2_loff_t)) &&
 	    ((channel->align == 0) ||
 	     (IS_ALIGNED(buf, channel->align) &&
+	      IS_ALIGNED(location, channel->align) &&
 	      IS_ALIGNED(size, channel->align)))) {
 		actual = pread(data->dev, buf, size, location);
 		if (actual == size)
@@ -256,12 +260,13 @@ static errcode_t raw_read_blk(io_channel channel,
 	}
 #endif /* HAVE_PREAD */
 
-	if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
+	if (ext2fs_llseek(data->dev, location, SEEK_SET) < 0) {
 		retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
 		goto error_out;
 	}
 	if ((channel->align == 0) ||
 	    (IS_ALIGNED(buf, channel->align) &&
+	     IS_ALIGNED(location, channel->align) &&
 	     IS_ALIGNED(size, channel->align))) {
 		actual = read(data->dev, buf, size);
 		if (actual != size) {
@@ -286,23 +291,39 @@ static errcode_t raw_read_blk(io_channel channel,
 	 * to the O_DIRECT rules, so we need to do this the hard way...
 	 */
 bounce_read:
+	if ((channel->block_size > channel->align) &&
+	    (channel->block_size % channel->align) == 0)
+		align_size = channel->block_size;
+	else
+		align_size = channel->align;
+	aligned_blk = location / align_size;
+	offset = location % align_size;
+
+	if (ext2fs_llseek(data->dev, aligned_blk * align_size, SEEK_SET) < 0) {
+		retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
+		goto error_out;
+	}
 	while (size > 0) {
 		mutex_lock(data, BOUNCE_MTX);
-		actual = read(data->dev, data->bounce, channel->block_size);
-		if (actual != channel->block_size) {
+		actual = read(data->dev, data->bounce, align_size);
+		if (actual != align_size) {
 			mutex_unlock(data, BOUNCE_MTX);
 			actual = really_read;
 			buf -= really_read;
 			size += really_read;
 			goto short_read;
 		}
-		actual = size;
-		if (size > channel->block_size)
-			actual = channel->block_size;
-		memcpy(buf, data->bounce, actual);
+		if ((actual + offset) > align_size)
+			actual = align_size - offset;
+		if (actual > size)
+			actual = size;
+		memcpy(buf, data->bounce + offset, actual);
+
 		really_read += actual;
 		size -= actual;
 		buf += actual;
+		offset = 0;
+		aligned_blk++;
 		mutex_unlock(data, BOUNCE_MTX);
 	}
 	return 0;
@@ -326,6 +347,8 @@ static errcode_t raw_write_blk(io_channel channel,
 	int		actual = 0;
 	errcode_t	retval;
 	const unsigned char *buf = bufv;
+	unsigned long long aligned_blk;
+	int		align_size, offset;
 
 	if (count == 1)
 		size = channel->block_size;
@@ -342,7 +365,7 @@ static errcode_t raw_write_blk(io_channel channel,
 	location = ((ext2_loff_t) block * channel->block_size) + data->offset;
 
 	if (data->flags & IO_FLAG_FORCE_BOUNCE) {
-		if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
+		if (ext2fs_llseek(data->dev, location, SEEK_SET) < 0) {
 			retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
 			goto error_out;
 		}
@@ -353,6 +376,7 @@ static errcode_t raw_write_blk(io_channel channel,
 	/* Try an aligned pwrite */
 	if ((channel->align == 0) ||
 	    (IS_ALIGNED(buf, channel->align) &&
+	     IS_ALIGNED(location, channel->align) &&
 	     IS_ALIGNED(size, channel->align))) {
 		actual = pwrite64(data->dev, buf, size, location);
 		if (actual == size)
@@ -363,6 +387,7 @@ static errcode_t raw_write_blk(io_channel channel,
 	if ((sizeof(off_t) >= sizeof(ext2_loff_t)) &&
 	    ((channel->align == 0) ||
 	     (IS_ALIGNED(buf, channel->align) &&
+	      IS_ALIGNED(location, channel->align) &&
 	      IS_ALIGNED(size, channel->align)))) {
 		actual = pwrite(data->dev, buf, size, location);
 		if (actual == size)
@@ -370,13 +395,14 @@ static errcode_t raw_write_blk(io_channel channel,
 	}
 #endif /* HAVE_PWRITE */
 
-	if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
+	if (ext2fs_llseek(data->dev, location, SEEK_SET) < 0) {
 		retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
 		goto error_out;
 	}
 
 	if ((channel->align == 0) ||
 	    (IS_ALIGNED(buf, channel->align) &&
+	     IS_ALIGNED(location, channel->align) &&
 	     IS_ALIGNED(size, channel->align))) {
 		actual = write(data->dev, buf, size);
 		if (actual < 0) {
@@ -400,40 +426,59 @@ static errcode_t raw_write_blk(io_channel channel,
 	 * to the O_DIRECT rules, so we need to do this the hard way...
 	 */
 bounce_write:
+	if ((channel->block_size > channel->align) &&
+	    (channel->block_size % channel->align) == 0)
+		align_size = channel->block_size;
+	else
+		align_size = channel->align;
+	aligned_blk = location / align_size;
+	offset = location % align_size;
+
 	while (size > 0) {
+		int actual_w;
+
 		mutex_lock(data, BOUNCE_MTX);
-		if (size < channel->block_size) {
+		if (size < align_size || offset) {
+			if (ext2fs_llseek(data->dev, aligned_blk * align_size,
+					  SEEK_SET) < 0) {
+				retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
+				goto error_out;
+			}
 			actual = read(data->dev, data->bounce,
-				      channel->block_size);
-			if (actual != channel->block_size) {
+				      align_size);
+			if (actual != align_size) {
 				if (actual < 0) {
 					mutex_unlock(data, BOUNCE_MTX);
 					retval = errno;
 					goto error_out;
 				}
 				memset((char *) data->bounce + actual, 0,
-				       channel->block_size - actual);
+				       align_size - actual);
 			}
 		}
 		actual = size;
-		if (size > channel->block_size)
-			actual = channel->block_size;
-		memcpy(data->bounce, buf, actual);
-		if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
+		if ((actual + offset) > align_size)
+			actual = align_size - offset;
+		if (actual > size)
+			actual = size;
+		memcpy(((char *)data->bounce) + offset, buf, actual);
+		if (ext2fs_llseek(data->dev, aligned_blk * align_size, SEEK_SET) < 0) {
 			retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
 			goto error_out;
 		}
-		actual = write(data->dev, data->bounce, channel->block_size);
+		actual_w = write(data->dev, data->bounce, align_size);
 		mutex_unlock(data, BOUNCE_MTX);
-		if (actual < 0) {
+		if (actual_w < 0) {
 			retval = errno;
 			goto error_out;
 		}
-		if (actual != channel->block_size)
+		if (actual_w != align_size)
 			goto short_write;
 		size -= actual;
 		buf += actual;
 		location += actual;
+		aligned_blk++;
+		offset = 0;
 	}
 	return 0;