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Add gang ABD child to parent gang ABD 

By design a gang ABD can not have another gang ABD as a child. This is
to make sure the logical offset in a gang ABD is consistent with the
individual ABDS it contains as children. If a gang ABD is added as a
child of a gang ABD we will add the individual children of the gang ABD
to the parent gang ABD. This allows for a consistent view of offsets
within the parent gang ABD.

Reviewed-by: Mark Maybee <mmaybee@cray.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Closes #10430
This commit is contained in:
Brian Atkinson 2020-07-24 22:09:20 -06:00 committed by GitHub
parent 8348fac30c
commit 6fba7bfd0e
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 55 additions and 1 deletions
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56
module/zfs/abd.c
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@ -139,12 +139,15 @@ abd_verify(abd_t *abd)
if (abd_is_linear(abd)) {
ASSERT3P(ABD_LINEAR_BUF(abd), !=, NULL);
} else if (abd_is_gang(abd)) {
uint_t child_sizes = 0;
for (abd_t *cabd = list_head(&ABD_GANG(abd).abd_gang_chain);
cabd != NULL;
cabd = list_next(&ABD_GANG(abd).abd_gang_chain, cabd)) {
ASSERT(list_link_active(&cabd->abd_gang_link));
child_sizes += cabd->abd_size;
abd_verify(cabd);
}
ASSERT3U(abd->abd_size, ==, child_sizes);
} else {
abd_verify_scatter(abd);
}
@ -377,6 +380,46 @@ abd_alloc_gang_abd(void)
return (abd);
}
/*
* Add a child gang ABD to a parent gang ABDs chained list.
*/
static void
abd_gang_add_gang(abd_t *pabd, abd_t *cabd, boolean_t free_on_free)
{
ASSERT(abd_is_gang(pabd));
ASSERT(abd_is_gang(cabd));
if (free_on_free) {
/*
* If the parent is responsible for freeing the child gang
* ABD we will just splice the childs children ABD list to
* the parents list and immediately free the child gang ABD
* struct. The parent gang ABDs children from the child gang
* will retain all the free_on_free settings after being
* added to the parents list.
*/
pabd->abd_size += cabd->abd_size;
list_move_tail(&ABD_GANG(pabd).abd_gang_chain,
&ABD_GANG(cabd).abd_gang_chain);
ASSERT(list_is_empty(&ABD_GANG(cabd).abd_gang_chain));
abd_verify(pabd);
abd_free_struct(cabd);
} else {
for (abd_t *child = list_head(&ABD_GANG(cabd).abd_gang_chain);
child != NULL;
child = list_next(&ABD_GANG(cabd).abd_gang_chain, child)) {
/*
* We always pass B_FALSE for free_on_free as it is the
* original child gang ABDs responsibilty to determine
* if any of its child ABDs should be free'd on the call
* to abd_free().
*/
abd_gang_add(pabd, child, B_FALSE);
}
abd_verify(pabd);
}
}
/*
* Add a child ABD to a gang ABD's chained list.
*/
@ -384,9 +427,20 @@ void
abd_gang_add(abd_t *pabd, abd_t *cabd, boolean_t free_on_free)
{
ASSERT(abd_is_gang(pabd));
ASSERT(!abd_is_gang(cabd));
abd_t *child_abd = NULL;
/*
* If the child being added is a gang ABD, we will add the
* childs ABDs to the parent gang ABD. This alllows us to account
* for the offset correctly in the parent gang ABD.
*/
if (abd_is_gang(cabd)) {
ASSERT(!list_link_active(&cabd->abd_gang_link));
ASSERT(!list_is_empty(&ABD_GANG(cabd).abd_gang_chain));
return (abd_gang_add_gang(pabd, cabd, free_on_free));
}
ASSERT(!abd_is_gang(cabd));
/*
* In order to verify that an ABD is not already part of
* another gang ABD, we must lock the child ABD's abd_mtx