Commit 65ccfe21 authored by Alex Elder's avatar Alex Elder
Browse files

rbd: split up rbd_get_segment() 



There are two places where rbd_get_segment() is called.  One, in
rbd_rq_fn(), only needs to know the length within a segment that an
I/O request should be.  The other, in rbd_do_op(), also needs the
name of the object and the offset within it for the I/O request.

Split out rbd_segment_name() into three dedicated functions:
    - rbd_segment_name() allocates and formats the name of the
      object for a segment containing a given rbd image offset
    - rbd_segment_offset() computes the offset within a segment for
      a given rbd image offset
    - rbd_segment_length() computes the length to use for I/O within
      a segment for a request, not to exceed the end of a segment
      object.

In the new functions be a bit more careful, checking for possible
error conditions:
    - watch for errors or overflows returned by snprintf()
    - catch (using BUG_ON()) potential overflow conditions
      when computing segment length

Signed-off-by: default avatarAlex Elder <elder@inktank.com>
Reviewed-by: default avatarYehuda Sadeh <yehuda@inktank.com>
parent df111be6

drivers/block/rbd.c

+40 −26
Original line number Diff line number Diff line
@@ -669,27 +669,47 @@ static void rbd_header_free(struct rbd_image_header *header) 
	header->snapc = NULL;

}



/*

 * get the actual striped segment name, offset and length

 */

static u64 rbd_get_segment(struct rbd_image_header *header,

			   const char *object_prefix,

			   u64 ofs, u64 len,

			   char *seg_name, u64 *segofs)

static char *rbd_segment_name(struct rbd_device *rbd_dev, u64 offset)

{

	char *name;

	u64 segment;

	int ret;



	name = kmalloc(RBD_MAX_SEG_NAME_LEN + 1, GFP_NOIO);

	if (!name)

		return NULL;

	segment = offset >> rbd_dev->header.obj_order;

	ret = snprintf(name, RBD_MAX_SEG_NAME_LEN, "%s.%012llx",

			rbd_dev->header.object_prefix, segment);

	if (ret < 0 || ret >= RBD_MAX_SEG_NAME_LEN) {

		pr_err("error formatting segment name for #%llu (%d)\n",

			segment, ret);

		kfree(name);

		name = NULL;

	}



	return name;

}



static u64 rbd_segment_offset(struct rbd_device *rbd_dev, u64 offset)

{

	u64 seg = ofs >> header->obj_order;

	u64 segment_size = (u64) 1 << rbd_dev->header.obj_order;



	if (seg_name)

		snprintf(seg_name, RBD_MAX_SEG_NAME_LEN,

			 "%s.%012llx", object_prefix, seg);

	return offset & (segment_size - 1);

}



	ofs = ofs & ((1 << header->obj_order) - 1);

	len = min_t(u64, len, (1 << header->obj_order) - ofs);

static u64 rbd_segment_length(struct rbd_device *rbd_dev,

				u64 offset, u64 length)

{

	u64 segment_size = (u64) 1 << rbd_dev->header.obj_order;



	if (segofs)

		*segofs = ofs;

	offset &= segment_size - 1;



	return len;

	BUG_ON(length > U64_MAX - offset);

	if (offset + length > segment_size)

		length = segment_size - offset;



	return length;

}



static int rbd_get_num_segments(struct rbd_image_header *header,
@@ -1127,14 +1147,11 @@ static int rbd_do_op(struct request *rq, 
	struct ceph_osd_req_op *ops;

	u32 payload_len;



	seg_name = kmalloc(RBD_MAX_SEG_NAME_LEN + 1, GFP_NOIO);

	seg_name = rbd_segment_name(rbd_dev, ofs);

	if (!seg_name)

		return -ENOMEM;



	seg_len = rbd_get_segment(&rbd_dev->header,

				  rbd_dev->header.object_prefix,

				  ofs, len,

				  seg_name, &seg_ofs);

	seg_len = rbd_segment_length(rbd_dev, ofs, len);

	seg_ofs = rbd_segment_offset(rbd_dev, ofs);



	payload_len = (flags & CEPH_OSD_FLAG_WRITE ? seg_len : 0);
@@ -1545,10 +1562,7 @@ static void rbd_rq_fn(struct request_queue *q) 
		do {

			/* a bio clone to be passed down to OSD req */

			dout("rq->bio->bi_vcnt=%hu\n", rq->bio->bi_vcnt);

			op_size = rbd_get_segment(&rbd_dev->header,

						  rbd_dev->header.object_prefix,

						  ofs, size,

						  NULL, NULL);

			op_size = rbd_segment_length(rbd_dev, ofs, size);

			kref_get(&coll->kref);

			bio = bio_chain_clone(&rq_bio, &next_bio, &bp,

					      op_size, GFP_ATOMIC);

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