virtio_blk: set the zone write granularitygrafted

virtblk_read_zoned_limits() reads the write granularity that the device
reports in virtio_blk_zoned_characteristics and assigns it to the
physical block size and to io_min, but never to the limit that is named
after it. queue_limits.zone_write_granularity is left at zero, so
blk_validate_zoned_limits() raises it to the logical block size:

	if (lim->zone_write_granularity < lim->logical_block_size)
		lim->zone_write_granularity = lim->logical_block_size;

A device that reports a granularity coarser than its logical block size,
which is what the field exists to express, therefore has it silently
reduced. A 512e host managed disk passed through to a guest reports a
logical block size of 512 and a write granularity of 4096, and the guest
ends up with a zone write granularity of 512.

bio_split_alignment() returns lim->zone_write_granularity if it is non-zero
and bio_split_io_at() may split a bio with as per bio_split_alignment().
This can real to the write getting rejected by the host drive, as the write
is not aligned to the physical block size.

zonefs also takes its block size from bdev_zone_write_granularity(), so it
would incorrectly use 512 on a disk that requires 4096.

sd_zbc_read_zones() sets the limit from the physical block size for the
same reason. NVMe ZNS and null_blk leave it unset, but the fallback
gives the right answer for them, as their write granularity is the
logical block size. virtio carries a separate value that may exceed it.

Set the zone write granularity from the value that the device reports.

Fixes: 95bfec41bd3d ("virtio-blk: add support for zoned block devices")
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Link: https://patch.msgid.link/20260918140641.2031075-2-cassel@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 180 insertions, 0 deletions

diff --git a/fs/kernel_read_file.c b/fs/kernel_read_file.c
new file mode 100644
index 000000000..9c2ba9240
--- /dev/null
+++ b/fs/kernel_read_file.c
@@ -0,0 +1,180 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/fs.h>
+#include <linux/fs_struct.h>
+#include <linux/kernel_read_file.h>
+#include <linux/security.h>
+#include <linux/vmalloc.h>
+
+/**
+ * kernel_read_file() - read file contents into a kernel buffer
+ *
+ * @file:	file to read from
+ * @offset:	where to start reading from (see below).
+ * @buf:	pointer to a "void *" buffer for reading into (if
+ *		*@buf is NULL, a buffer will be allocated, and
+ *		@buf_size will be ignored)
+ * @buf_size:	size of buf, if already allocated. If @buf not
+ *		allocated, this is the largest size to allocate.
+ * @file_size:	if non-NULL, the full size of @file will be
+ *		written here.
+ * @id:		the kernel_read_file_id identifying the type of
+ *		file contents being read (for LSMs to examine)
+ *
+ * @offset must be 0 unless both @buf and @file_size are non-NULL
+ * (i.e. the caller must be expecting to read partial file contents
+ * via an already-allocated @buf, in at most @buf_size chunks, and
+ * will be able to determine when the entire file was read by
+ * checking @file_size). This isn't a recommended way to read a
+ * file, though, since it is possible that the contents might
+ * change between calls to kernel_read_file().
+ *
+ * Returns number of bytes read (no single read will be bigger
+ * than SSIZE_MAX), or negative on error.
+ *
+ */
+ssize_t kernel_read_file(struct file *file, loff_t offset, void **buf,
+			 size_t buf_size, size_t *file_size,
+			 enum kernel_read_file_id id)
+{
+	loff_t i_size, pos;
+	ssize_t copied;
+	void *allocated = NULL;
+	bool whole_file;
+	int ret;
+
+	if (offset != 0 && (!*buf || !file_size))
+		return -EINVAL;
+
+	if (!S_ISREG(file_inode(file)->i_mode))
+		return -EINVAL;
+
+	ret = deny_write_access(file);
+	if (ret)
+		return ret;
+
+	i_size = i_size_read(file_inode(file));
+	if (i_size <= 0) {
+		ret = -EINVAL;
+		goto out;
+	}
+	/* The file is too big for sane activities. */
+	if (i_size > SSIZE_MAX) {
+		ret = -EFBIG;
+		goto out;
+	}
+	/* The entire file cannot be read in one buffer. */
+	if (!file_size && offset == 0 && i_size > buf_size) {
+		ret = -EFBIG;
+		goto out;
+	}
+
+	whole_file = (offset == 0 && i_size <= buf_size);
+	ret = security_kernel_read_file(file, id, whole_file);
+	if (ret)
+		goto out;
+
+	if (file_size)
+		*file_size = i_size;
+
+	if (!*buf)
+		*buf = allocated = vmalloc(i_size);
+	if (!*buf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	pos = offset;
+	copied = 0;
+	while (copied < buf_size) {
+		ssize_t bytes;
+		size_t wanted = min_t(size_t, buf_size - copied,
+					      i_size - pos);
+
+		bytes = kernel_read(file, *buf + copied, wanted, &pos);
+		if (bytes < 0) {
+			ret = bytes;
+			goto out_free;
+		}
+
+		if (bytes == 0)
+			break;
+		copied += bytes;
+	}
+
+	if (whole_file) {
+		if (pos != i_size) {
+			ret = -EIO;
+			goto out_free;
+		}
+
+		ret = security_kernel_post_read_file(file, *buf, i_size, id);
+	}
+
+out_free:
+	if (ret < 0) {
+		if (allocated) {
+			vfree(*buf);
+			*buf = NULL;
+		}
+	}
+
+out:
+	allow_write_access(file);
+	return ret == 0 ? copied : ret;
+}
+EXPORT_SYMBOL_GPL(kernel_read_file);
+
+ssize_t kernel_read_file_from_path(const char *path, loff_t offset, void **buf,
+				   size_t buf_size, size_t *file_size,
+				   enum kernel_read_file_id id)
+{
+	struct file *file;
+	ssize_t ret;
+
+	if (!path || !*path)
+		return -EINVAL;
+
+	file = filp_open(path, O_RDONLY, 0);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	ret = kernel_read_file(file, offset, buf, buf_size, file_size, id);
+	fput(file);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
+
+ssize_t kernel_read_file_from_path_initns(const char *path, loff_t offset,
+					  void **buf, size_t buf_size,
+					  size_t *file_size,
+					  enum kernel_read_file_id id)
+{
+	struct file *file;
+	ssize_t ret;
+
+	if (!path || !*path)
+		return -EINVAL;
+
+	scoped_with_init_fs()
+		file = filp_open(path, O_RDONLY, 0);
+	if (IS_ERR(file))
+		return PTR_ERR(file);
+
+	ret = kernel_read_file(file, offset, buf, buf_size, file_size, id);
+	fput(file);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns);
+
+ssize_t kernel_read_file_from_fd(int fd, loff_t offset, void **buf,
+				 size_t buf_size, size_t *file_size,
+				 enum kernel_read_file_id id)
+{
+	CLASS(fd, f)(fd);
+
+	if (fd_empty(f) || !(fd_file(f)->f_mode & FMODE_READ))
+		return -EBADF;
+
+	return kernel_read_file(fd_file(f), offset, buf, buf_size, file_size, id);
+}
+EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);