From d7e4b30a672c1d7eb77dbbe2cdcf14cac102839a Mon Sep 17 00:00:00 2001 From: Brian Behlendorf Date: Mon, 8 Oct 2018 14:58:21 -0700 Subject: [PATCH] Add zfs_refcount_transfer_ownership_many() 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 Signed-off-by: Tom Caputi Signed-off-by: Brian Behlendorf Closes #7219 Closes #8000 --- include/sys/refcount.h | 7 +++++-- module/zfs/arc.c | 8 ++++---- module/zfs/refcount.c | 15 ++++++++++++--- 3 files changed, 21 insertions(+), 9 deletions(-) diff --git a/include/sys/refcount.h b/include/sys/refcount.h index 0059a245ee..e982faeba0 100644 --- a/include/sys/refcount.h +++ b/include/sys/refcount.h @@ -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() diff --git a/module/zfs/arc.c b/module/zfs/arc.c index ae912ee6eb..e5d88fe5d7 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -3081,8 +3081,8 @@ arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) * refcount ownership to the hdr since it always owns * the refcount whenever an arc_buf_t is shared. */ - zfs_refcount_transfer_ownership(&hdr->b_l1hdr.b_state->arcs_size, - buf, hdr); + zfs_refcount_transfer_ownership_many(&hdr->b_l1hdr.b_state->arcs_size, + arc_hdr_size(hdr), buf, hdr); hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf)); abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd, HDR_ISTYPE_METADATA(hdr)); @@ -3110,8 +3110,8 @@ arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf) * We are no longer sharing this buffer so we need * to transfer its ownership to the rightful owner. */ - zfs_refcount_transfer_ownership(&hdr->b_l1hdr.b_state->arcs_size, - hdr, buf); + zfs_refcount_transfer_ownership_many(&hdr->b_l1hdr.b_state->arcs_size, + arc_hdr_size(hdr), hdr, buf); arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA); abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd); abd_put(hdr->b_l1hdr.b_pabd); diff --git a/module/zfs/refcount.c b/module/zfs/refcount.c index 0a93aafb13..bcaa6d3875 100644 --- a/module/zfs/refcount.c +++ b/module/zfs/refcount.c @@ -234,8 +234,8 @@ zfs_refcount_transfer(zfs_refcount_t *dst, zfs_refcount_t *src) } void -zfs_refcount_transfer_ownership(zfs_refcount_t *rc, void *current_holder, - void *new_holder) +zfs_refcount_transfer_ownership_many(zfs_refcount_t *rc, uint64_t number, + void *current_holder, void *new_holder) { reference_t *ref; boolean_t found = B_FALSE; @@ -248,7 +248,8 @@ zfs_refcount_transfer_ownership(zfs_refcount_t *rc, void *current_holder, for (ref = list_head(&rc->rc_list); ref; ref = list_next(&rc->rc_list, ref)) { - if (ref->ref_holder == current_holder) { + if (ref->ref_holder == current_holder && + ref->ref_number == number) { ref->ref_holder = new_holder; found = B_TRUE; break; @@ -258,6 +259,14 @@ zfs_refcount_transfer_ownership(zfs_refcount_t *rc, void *current_holder, mutex_exit(&rc->rc_mtx); } +void +zfs_refcount_transfer_ownership(zfs_refcount_t *rc, void *current_holder, + void *new_holder) +{ + return (zfs_refcount_transfer_ownership_many(rc, 1, current_holder, + new_holder)); +} + /* * If tracking is enabled, return true if a reference exists that matches * the "holder" tag. If tracking is disabled, then return true if a reference