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Add zfs_refcount_transfer_ownership_many()

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When debugging is enabled and a zfs_refcount_t contains multiple holders
using the same key, but different ref_counts, the wrong reference_t may
be transferred.  Add a zfs_refcount_transfer_ownership_many() function,
like the existing zfs_refcount_*_many() functions, to match and transfer
the correct refcount_t;

This issue may occur when using encryption with refcount debugging
enabled.  An arc_buf_hdr_t can have references for both the
hdr->b_l1hdr.b_pabd and hdr->b_crypt_hdr.b_rabd both of which use
the hdr as the reference holder.  When unsharing the buffer the
p_abd should be transferred.

This issue does not impact production builds because refcount holders
are not tracked.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #7219
Closes #8000
This commit is contained in:
Brian Behlendorf
2018-10-08 14:58:21 -07:00
parent 4cbde2ecbf
commit d7e4b30a67
3 changed files with 21 additions and 9 deletions
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include/sys/refcount.h
+5 -2
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@@ -76,6 +76,8 @@ int64_t zfs_refcount_add_many(zfs_refcount_t *, uint64_t, void *);
int64_t zfs_refcount_remove_many(zfs_refcount_t *, uint64_t, void *);
void zfs_refcount_transfer(zfs_refcount_t *, zfs_refcount_t *);
void zfs_refcount_transfer_ownership(zfs_refcount_t *, void *, void *);
void zfs_refcount_transfer_ownership_many(zfs_refcount_t *, uint64_t,
void *, void *);
boolean_t zfs_refcount_held(zfs_refcount_t *, void *);
boolean_t zfs_refcount_not_held(zfs_refcount_t *, void *);
@@ -106,8 +108,9 @@ typedef struct refcount {
atomic_add_64(&(src)->rc_count, -__tmp); \
atomic_add_64(&(dst)->rc_count, __tmp); \
}
#define zfs_refcount_transfer_ownership(rc, current_holder, new_holder) (void)0
#define zfs_refcount_held(rc, holder) ((rc)->rc_count > 0)
#define zfs_refcount_transfer_ownership(rc, ch, nh) ((void)0)
#define zfs_refcount_transfer_ownership_many(rc, nr, ch, nh) ((void)0)
#define zfs_refcount_held(rc, holder) ((rc)->rc_count > 0)
#define zfs_refcount_not_held(rc, holder) (B_TRUE)
#define zfs_refcount_init()