From 65ccfe21dd8fb402547bb1c50bbc2737c4ef37b8 Mon Sep 17 00:00:00 2001 From: Alex Elder Date: Thu, 9 Aug 2012 10:33:26 -0700 Subject: [PATCH] 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 Reviewed-by: Yehuda Sadeh --- drivers/block/rbd.c | 66 +++++++++++++++++++++++++++------------------ 1 file changed, 40 insertions(+), 26 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 6da6990a7b57..7ba70c49bbdb 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -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); +} + +static u64 rbd_segment_length(struct rbd_device *rbd_dev, + u64 offset, u64 length) +{ + u64 segment_size = (u64) 1 << rbd_dev->header.obj_order; - ofs = ofs & ((1 << header->obj_order) - 1); - len = min_t(u64, len, (1 << header->obj_order) - ofs); + offset &= segment_size - 1; - if (segofs) - *segofs = ofs; + BUG_ON(length > U64_MAX - offset); + if (offset + length > segment_size) + length = segment_size - offset; - return len; + 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); -- 2.20.1