Annotate gendisk.part_tbl and disk_part_tbl.part dereferences with rcu_dereference_protected(). This patch does not change the behavior of the modified code but ensures that sparse does not complain about disk->part_tbl manipulations nor about part_tbl->part accesses. Additionally, improve documentation of the locking requirements of the modified functions.
Signed-off-by: Bart Van Assche <[email protected]> Cc: Tejun Heo <[email protected]> Cc: Jan Kara <[email protected]> Cc: Dan Williams <[email protected]> Cc: Christoph Hellwig <[email protected]> --- block/genhd.c | 15 ++++++++++----- block/partition-generic.c | 15 ++++++++++++--- 2 files changed, 22 insertions(+), 8 deletions(-) diff --git a/block/genhd.c b/block/genhd.c index 3dc4d115480f..2367087cdb7c 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -1127,12 +1127,13 @@ static const struct attribute_group *disk_attr_groups[] = { * original ptbl is freed using RCU callback. * * LOCKING: - * Matching bd_mutx locked. + * Matching bd_mutex locked or the caller is the only user of @disk. */ static void disk_replace_part_tbl(struct gendisk *disk, struct disk_part_tbl *new_ptbl) { - struct disk_part_tbl *old_ptbl = disk->part_tbl; + struct disk_part_tbl *old_ptbl = + rcu_dereference_protected(disk->part_tbl, 1); rcu_assign_pointer(disk->part_tbl, new_ptbl); @@ -1151,14 +1152,16 @@ static void disk_replace_part_tbl(struct gendisk *disk, * uses RCU to allow unlocked dereferencing for stats and other stuff. * * LOCKING: - * Matching bd_mutex locked, might sleep. + * Matching bd_mutex locked or the caller is the only user of @disk. + * Might sleep. * * RETURNS: * 0 on success, -errno on failure. */ int disk_expand_part_tbl(struct gendisk *disk, int partno) { - struct disk_part_tbl *old_ptbl = disk->part_tbl; + struct disk_part_tbl *old_ptbl = + rcu_dereference_protected(disk->part_tbl, 1); struct disk_part_tbl *new_ptbl; int len = old_ptbl ? old_ptbl->len : 0; int i, target; @@ -1352,6 +1355,7 @@ EXPORT_SYMBOL(alloc_disk); struct gendisk *alloc_disk_node(int minors, int node_id) { struct gendisk *disk; + struct disk_part_tbl *ptbl; disk = kzalloc_node(sizeof(struct gendisk), GFP_KERNEL, node_id); if (disk) { @@ -1365,7 +1369,8 @@ struct gendisk *alloc_disk_node(int minors, int node_id) kfree(disk); return NULL; } - disk->part_tbl->part[0] = &disk->part0; + ptbl = rcu_dereference_protected(disk->part_tbl, 1); + rcu_assign_pointer(ptbl->part[0], &disk->part0); /* * set_capacity() and get_capacity() currently don't use diff --git a/block/partition-generic.c b/block/partition-generic.c index fa5049a4d99b..1745a9659517 100644 --- a/block/partition-generic.c +++ b/block/partition-generic.c @@ -252,15 +252,20 @@ void __delete_partition(struct percpu_ref *ref) call_rcu(&part->rcu_head, delete_partition_rcu_cb); } +/* + * Must be called either with bd_mutex held, before a disk can be opened or + * after all disk users are gone. + */ void delete_partition(struct gendisk *disk, int partno) { - struct disk_part_tbl *ptbl = disk->part_tbl; + struct disk_part_tbl *ptbl = + rcu_dereference_protected(disk->part_tbl, 1); struct hd_struct *part; if (partno >= ptbl->len) return; - part = ptbl->part[partno]; + part = rcu_dereference_protected(ptbl->part[partno], 1); if (!part) return; @@ -280,6 +285,10 @@ static ssize_t whole_disk_show(struct device *dev, static DEVICE_ATTR(whole_disk, S_IRUSR | S_IRGRP | S_IROTH, whole_disk_show, NULL); +/* + * Must be called either with bd_mutex held, before a disk can be opened or + * after all disk users are gone. + */ struct hd_struct *add_partition(struct gendisk *disk, int partno, sector_t start, sector_t len, int flags, struct partition_meta_info *info) @@ -295,7 +304,7 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno, err = disk_expand_part_tbl(disk, partno); if (err) return ERR_PTR(err); - ptbl = disk->part_tbl; + ptbl = rcu_dereference_protected(disk->part_tbl, 1); if (ptbl->part[partno]) return ERR_PTR(-EBUSY); -- 2.14.0
