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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: Alex Elder <elder@inktank.com>
Reviewed-by: Yehuda Sadeh <yehuda@inktank.com>
This commit is contained in:
Alex Elder 2012-08-09 10:33:26 -07:00
parent df111be631
commit 65ccfe21dd
1 changed files with 40 additions and 26 deletions
drivers/block
rbd.c

66
drivers/block/rbd.c
View File

@ -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)
{
u64 seg = ofs >> header->obj_order;
char *name;
u64 segment;
int ret;
if (seg_name)
snprintf(seg_name, RBD_MAX_SEG_NAME_LEN,
"%s.%012llx", object_prefix, seg);
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;
}
ofs = ofs & ((1 << header->obj_order) - 1);
len = min_t(u64, len, (1 << header->obj_order) - ofs);
return name;
}
if (segofs)
*segofs = ofs;
static u64 rbd_segment_offset(struct rbd_device *rbd_dev, u64 offset)
{
u64 segment_size = (u64) 1 << rbd_dev->header.obj_order;
return len;
return offset & (segment_size - 1);
}
static u64 rbd_segment_length(struct rbd_device *rbd_dev,
u64 offset, u64 length)
{
u64 segment_size = (u64) 1 << rbd_dev->header.obj_order;
offset &= segment_size - 1;
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);