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md: make merge_bvec_fn more robust in face of personality changes.
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There is no locking around calls to merge_bvec_fn(), so
it is possible that calls which coincide with a level (or personality)
change could go wrong.

So create a central dispatch point for these functions and use
rcu_read_lock().
If the array is suspended, reject any merge that can be rejected.
If not, we know it is safe to call the function.

Signed-off-by: NeilBrown <neilb@suse.de>
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NeilBrown committed Feb 3, 2015
1 parent 5c675f8 commit 64590f4
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Showing 7 changed files with 42 additions and 20 deletions.
6 changes: 2 additions & 4 deletions drivers/md/linear.c
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Original file line number Diff line number Diff line change
Expand Up @@ -60,11 +60,10 @@ static inline struct dev_info *which_dev(struct mddev *mddev, sector_t sector)
*
* Return amount of bytes we can take at this offset
*/
static int linear_mergeable_bvec(struct request_queue *q,
static int linear_mergeable_bvec(struct mddev *mddev,
struct bvec_merge_data *bvm,
struct bio_vec *biovec)
{
struct mddev *mddev = q->queuedata;
struct dev_info *dev0;
unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
Expand Down Expand Up @@ -213,8 +212,6 @@ static int linear_run (struct mddev *mddev)
mddev->private = conf;
md_set_array_sectors(mddev, linear_size(mddev, 0, 0));

blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);

ret = md_integrity_register(mddev);
if (ret) {
kfree(conf);
Expand Down Expand Up @@ -361,6 +358,7 @@ static struct md_personality linear_personality =
.hot_add_disk = linear_add,
.size = linear_size,
.congested = linear_congested,
.mergeable_bvec = linear_mergeable_bvec,
};

static int __init linear_init (void)
Expand Down
24 changes: 24 additions & 0 deletions drivers/md/md.c
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Original file line number Diff line number Diff line change
Expand Up @@ -339,6 +339,29 @@ static int md_congested(void *data, int bits)
return mddev_congested(mddev, bits);
}

static int md_mergeable_bvec(struct request_queue *q,
struct bvec_merge_data *bvm,
struct bio_vec *biovec)
{
struct mddev *mddev = q->queuedata;
int ret;
rcu_read_lock();
if (mddev->suspended) {
/* Must always allow one vec */
if (bvm->bi_size == 0)
ret = biovec->bv_len;
else
ret = 0;
} else {
struct md_personality *pers = mddev->pers;
if (pers && pers->mergeable_bvec)
ret = pers->mergeable_bvec(mddev, bvm, biovec);
else
ret = biovec->bv_len;
}
rcu_read_unlock();
return ret;
}
/*
* Generic flush handling for md
*/
Expand Down Expand Up @@ -4925,6 +4948,7 @@ int md_run(struct mddev *mddev)
if (mddev->queue) {
mddev->queue->backing_dev_info.congested_data = mddev;
mddev->queue->backing_dev_info.congested_fn = md_congested;
blk_queue_merge_bvec(mddev->queue, md_mergeable_bvec);
}
if (mddev->pers->sync_request) {
if (mddev->kobj.sd &&
Expand Down
4 changes: 4 additions & 0 deletions drivers/md/md.h
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Original file line number Diff line number Diff line change
Expand Up @@ -499,6 +499,10 @@ struct md_personality
/* congested implements bdi.congested_fn().
* Will not be called while array is 'suspended' */
int (*congested)(struct mddev *mddev, int bits);
/* mergeable_bvec is use to implement ->merge_bvec_fn */
int (*mergeable_bvec)(struct mddev *mddev,
struct bvec_merge_data *bvm,
struct bio_vec *biovec);
};

struct md_sysfs_entry {
Expand Down
7 changes: 3 additions & 4 deletions drivers/md/raid0.c
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Original file line number Diff line number Diff line change
Expand Up @@ -350,17 +350,16 @@ static struct md_rdev *map_sector(struct mddev *mddev, struct strip_zone *zone,

/**
* raid0_mergeable_bvec -- tell bio layer if two requests can be merged
* @q: request queue
* @mddev: the md device
* @bvm: properties of new bio
* @biovec: the request that could be merged to it.
*
* Return amount of bytes we can accept at this offset
*/
static int raid0_mergeable_bvec(struct request_queue *q,
static int raid0_mergeable_bvec(struct mddev *mddev,
struct bvec_merge_data *bvm,
struct bio_vec *biovec)
{
struct mddev *mddev = q->queuedata;
struct r0conf *conf = mddev->private;
sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
sector_t sector_offset = sector;
Expand Down Expand Up @@ -465,7 +464,6 @@ static int raid0_run(struct mddev *mddev)
mddev->queue->backing_dev_info.ra_pages = 2* stripe;
}

blk_queue_merge_bvec(mddev->queue, raid0_mergeable_bvec);
dump_zones(mddev);

ret = md_integrity_register(mddev);
Expand Down Expand Up @@ -724,6 +722,7 @@ static struct md_personality raid0_personality=
.takeover = raid0_takeover,
.quiesce = raid0_quiesce,
.congested = raid0_congested,
.mergeable_bvec = raid0_mergeable_bvec,
};

static int __init raid0_init (void)
Expand Down
6 changes: 2 additions & 4 deletions drivers/md/raid1.c
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Original file line number Diff line number Diff line change
Expand Up @@ -701,11 +701,10 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
return best_disk;
}

static int raid1_mergeable_bvec(struct request_queue *q,
static int raid1_mergeable_bvec(struct mddev *mddev,
struct bvec_merge_data *bvm,
struct bio_vec *biovec)
{
struct mddev *mddev = q->queuedata;
struct r1conf *conf = mddev->private;
sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
int max = biovec->bv_len;
Expand Down Expand Up @@ -2946,8 +2945,6 @@ static int run(struct mddev *mddev)
md_set_array_sectors(mddev, raid1_size(mddev, 0, 0));

if (mddev->queue) {
blk_queue_merge_bvec(mddev->queue, raid1_mergeable_bvec);

if (discard_supported)
queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
mddev->queue);
Expand Down Expand Up @@ -3183,6 +3180,7 @@ static struct md_personality raid1_personality =
.quiesce = raid1_quiesce,
.takeover = raid1_takeover,
.congested = raid1_congested,
.mergeable_bvec = raid1_mergeable_bvec,
};

static int __init raid_init(void)
Expand Down
7 changes: 3 additions & 4 deletions drivers/md/raid10.c
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Original file line number Diff line number Diff line change
Expand Up @@ -674,19 +674,18 @@ static sector_t raid10_find_virt(struct r10conf *conf, sector_t sector, int dev)

/**
* raid10_mergeable_bvec -- tell bio layer if a two requests can be merged
* @q: request queue
* @mddev: the md device
* @bvm: properties of new bio
* @biovec: the request that could be merged to it.
*
* Return amount of bytes we can accept at this offset
* This requires checking for end-of-chunk if near_copies != raid_disks,
* and for subordinate merge_bvec_fns if merge_check_needed.
*/
static int raid10_mergeable_bvec(struct request_queue *q,
static int raid10_mergeable_bvec(struct mddev *mddev,
struct bvec_merge_data *bvm,
struct bio_vec *biovec)
{
struct mddev *mddev = q->queuedata;
struct r10conf *conf = mddev->private;
sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
int max;
Expand Down Expand Up @@ -3756,7 +3755,6 @@ static int run(struct mddev *mddev)
stripe /= conf->geo.near_copies;
if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
blk_queue_merge_bvec(mddev->queue, raid10_mergeable_bvec);
}

if (md_integrity_register(mddev))
Expand Down Expand Up @@ -4717,6 +4715,7 @@ static struct md_personality raid10_personality =
.start_reshape = raid10_start_reshape,
.finish_reshape = raid10_finish_reshape,
.congested = raid10_congested,
.mergeable_bvec = raid10_mergeable_bvec,
};

static int __init raid_init(void)
Expand Down
8 changes: 4 additions & 4 deletions drivers/md/raid5.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4170,11 +4170,10 @@ static int raid5_congested(struct mddev *mddev, int bits)
/* We want read requests to align with chunks where possible,
* but write requests don't need to.
*/
static int raid5_mergeable_bvec(struct request_queue *q,
static int raid5_mergeable_bvec(struct mddev *mddev,
struct bvec_merge_data *bvm,
struct bio_vec *biovec)
{
struct mddev *mddev = q->queuedata;
sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
int max;
unsigned int chunk_sectors = mddev->chunk_sectors;
Expand Down Expand Up @@ -6237,8 +6236,6 @@ static int run(struct mddev *mddev)
if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
mddev->queue->backing_dev_info.ra_pages = 2 * stripe;

blk_queue_merge_bvec(mddev->queue, raid5_mergeable_bvec);

chunk_size = mddev->chunk_sectors << 9;
blk_queue_io_min(mddev->queue, chunk_size);
blk_queue_io_opt(mddev->queue, chunk_size *
Expand Down Expand Up @@ -7113,6 +7110,7 @@ static struct md_personality raid6_personality =
.quiesce = raid5_quiesce,
.takeover = raid6_takeover,
.congested = raid5_congested,
.mergeable_bvec = raid5_mergeable_bvec,
};
static struct md_personality raid5_personality =
{
Expand All @@ -7136,6 +7134,7 @@ static struct md_personality raid5_personality =
.quiesce = raid5_quiesce,
.takeover = raid5_takeover,
.congested = raid5_congested,
.mergeable_bvec = raid5_mergeable_bvec,
};

static struct md_personality raid4_personality =
Expand All @@ -7160,6 +7159,7 @@ static struct md_personality raid4_personality =
.quiesce = raid5_quiesce,
.takeover = raid4_takeover,
.congested = raid5_congested,
.mergeable_bvec = raid5_mergeable_bvec,
};

static int __init raid5_init(void)
Expand Down

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