On Tue, Oct 22, 2019 at 09:38:47AM -0400, Brian Foster wrote:
> On Wed, Oct 09, 2019 at 09:49:30AM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> >
> > Convert the xbitmap code to use interval trees instead of linked lists.
> > This reduces the amount of coding required to handle the disunion
> > operation and in the future will make it easier to set bits in arbitrary
> > order yet later be able to extract maximally sized extents, which we'll
> > need for rebuilding certain structures.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > ---
>
> Looks mostly straightforward provided my lack of knowledge on interval
> trees. A few random comments..
>
> > fs/xfs/Kconfig | 1
> > fs/xfs/scrub/agheader_repair.c | 4 -
> > fs/xfs/scrub/bitmap.c | 292 +++++++++++++++++-----------------------
> > fs/xfs/scrub/bitmap.h | 13 +-
> > 4 files changed, 135 insertions(+), 175 deletions(-)
> >
> >
> ...
> > diff --git a/fs/xfs/scrub/bitmap.c b/fs/xfs/scrub/bitmap.c
> > index 1041f17f6bb6..e1da103bce78 100644
> > --- a/fs/xfs/scrub/bitmap.c
> > +++ b/fs/xfs/scrub/bitmap.c
> > @@ -12,30 +12,105 @@
> > #include "xfs_btree.h"
> > #include "scrub/bitmap.h"
> >
> > -#define for_each_xbitmap_extent(bex, n, bitmap) \
> > - list_for_each_entry_safe((bex), (n), &(bitmap)->list, list)
> > +#define for_each_xbitmap_extent(itn, n, bitmap) \
> > + rbtree_postorder_for_each_entry_safe((itn), (n), \
> > + &(bitmap)->root.rb_root, rb)
> >
>
> I'm not familiar with the interval tree, but the header for this rbtree_
> macro mentions it is unsafe with respect to rbtree_erase(). Is that a
> concern for any of the users that might call interval_tree_remove()? It
> looks like that calls down into rb_erase_augmented(), but it's not clear
> to me if that's a problem..
It's not clear to me either, but the xbitmap iteration functions have
the implicit requirement that you can't edit the xbitmap while walking
it, so I'll add that to the documentation.
Note that none of the callers in my dev tree do that; the agheader
repair code uses disunion to get around that limitation.
As for xbitmap_destroy... yeah, I think that should use a
interval_tree_iter_first loop and not the for_* macro, since a tree
rebalance could upset things.
> > -/*
> > - * Set a range of this bitmap. Caller must ensure the range is not set.
> > - *
> > - * This is the logical equivalent of bitmap |= mask(start, len).
> > - */
> > +/* Clear a range of this bitmap. */
> > +static void
> > +__xbitmap_clear(
> > + struct xbitmap *bitmap,
> > + uint64_t start,
> > + uint64_t last)
> > +{
> > + struct interval_tree_node *itn;
> > +
> > + while ((itn = interval_tree_iter_first(&bitmap->root, start, last))) {
> > + if (itn->start < start) {
> > + /* overlaps with the left side of the clearing range */
> > + interval_tree_remove(itn, &bitmap->root);
> > + itn->last = start - 1;
> > + interval_tree_insert(itn, &bitmap->root);
> > + } else if (itn->last > last) {
> > + /* overlaps with the right side of the clearing range */
> > + interval_tree_remove(itn, &bitmap->root);
> > + itn->start = last + 1;
> > + interval_tree_insert(itn, &bitmap->root);
> > + break;
> > + } else {
> > + /* in the middle of the clearing range */
> > + interval_tree_remove(itn, &bitmap->root);
> > + kmem_free(itn);
> > + }
> > + }
> > +}
> > +
> > +/* Clear a range of this bitmap. */
> > +void
> > +xbitmap_clear(
> > + struct xbitmap *bitmap,
> > + uint64_t start,
> > + uint64_t len)
> > +{
> > + __xbitmap_clear(bitmap, start, start + len - 1);
> > +}
>
> It seems unnecessary to split the functions like this just to preserve
> the interface. Could we have the other __xbitmap_clear() caller just
> calculate the len itself and call xbitmap_clear() instead?
Ok.
> > +
> > +/* Set a range of this bitmap. */
> > int
> > xbitmap_set(
> > - struct xbitmap *bitmap,
> > - uint64_t start,
> > - uint64_t len)
> > + struct xbitmap *bitmap,
> > + uint64_t start,
> > + uint64_t len)
> > {
> > - struct xbitmap_range *bmr;
> > + struct interval_tree_node *left;
> > + struct interval_tree_node *right;
> > + uint64_t last = start + len - 1;
> >
> > - bmr = kmem_alloc(sizeof(struct xbitmap_range), KM_MAYFAIL);
> > - if (!bmr)
> > - return -ENOMEM;
> > + /* Is this whole range already set? */
> > + left = interval_tree_iter_first(&bitmap->root, start, last);
> > + if (left && left->start <= start && left->last >= last)
> > + return 0;
> >
> > - INIT_LIST_HEAD(&bmr->list);
> > - bmr->start = start;
> > - bmr->len = len;
> > - list_add_tail(&bmr->list, &bitmap->list);
> > + /* Clear out everything in the range we want to set. */
> > + xbitmap_clear(bitmap, start, len);
> > +
> > + /* Do we have a left-adjacent extent? */
> > + left = interval_tree_iter_first(&bitmap->root, start - 1, start - 1);
> > + if (left && left->last + 1 != start)
> > + left = NULL;
> > +
> > + /* Do we have a right-adjacent extent? */
> > + right = interval_tree_iter_first(&bitmap->root, last + 1, last + 1);
> > + if (right && right->start != last + 1)
> > + right = NULL;
>
> If we just cleared the range to set above, shouldn't these left/right
> checks always return an adjacent extent or NULL? It seems harmless,
> FWIW, but I'm curious if the logic is necessary.
They should be; I'll turn them into ASSERTs. Thanks for reading this
series!
--D
> Brian
>
> > +
> > + if (left && right) {
> > + /* combine left and right adjacent extent */
> > + interval_tree_remove(left, &bitmap->root);
> > + interval_tree_remove(right, &bitmap->root);
> > + left->last = right->last;
> > + interval_tree_insert(left, &bitmap->root);
> > + kmem_free(right);
> > + } else if (left) {
> > + /* combine with left extent */
> > + interval_tree_remove(left, &bitmap->root);
> > + left->last = last;
> > + interval_tree_insert(left, &bitmap->root);
> > + } else if (right) {
> > + /* combine with right extent */
> > + interval_tree_remove(right, &bitmap->root);
> > + right->start = start;
> > + interval_tree_insert(right, &bitmap->root);
> > + } else {
> > + /* add an extent */
> > + left = kmem_alloc(sizeof(struct interval_tree_node),
> > + KM_MAYFAIL);
> > + if (!left)
> > + return -ENOMEM;
> > + left->start = start;
> > + left->last = last;
> > + interval_tree_insert(left, &bitmap->root);
> > + }
> >
> > return 0;
> > }
> > @@ -43,14 +118,13 @@ xbitmap_set(
> > /* Free everything related to this bitmap. */
> > void
> > xbitmap_destroy(
> > - struct xbitmap *bitmap)
> > + struct xbitmap *bitmap)
> > {
> > - struct xbitmap_range *bmr;
> > - struct xbitmap_range *n;
> > + struct interval_tree_node *itn, *p;
> >
> > - for_each_xbitmap_extent(bmr, n, bitmap) {
> > - list_del(&bmr->list);
> > - kmem_free(bmr);
> > + for_each_xbitmap_extent(itn, p, bitmap) {
> > + interval_tree_remove(itn, &bitmap->root);
> > + kfree(itn);
> > }
> > }
> >
> > @@ -59,27 +133,7 @@ void
> > xbitmap_init(
> > struct xbitmap *bitmap)
> > {
> > - INIT_LIST_HEAD(&bitmap->list);
> > -}
> > -
> > -/* Compare two btree extents. */
> > -static int
> > -xbitmap_range_cmp(
> > - void *priv,
> > - struct list_head *a,
> > - struct list_head *b)
> > -{
> > - struct xbitmap_range *ap;
> > - struct xbitmap_range *bp;
> > -
> > - ap = container_of(a, struct xbitmap_range, list);
> > - bp = container_of(b, struct xbitmap_range, list);
> > -
> > - if (ap->start > bp->start)
> > - return 1;
> > - if (ap->start < bp->start)
> > - return -1;
> > - return 0;
> > + bitmap->root = RB_ROOT_CACHED;
> > }
> >
> > /*
> > @@ -96,118 +150,19 @@ xbitmap_range_cmp(
> > *
> > * This is the logical equivalent of bitmap &= ~sub.
> > */
> > -#define LEFT_ALIGNED (1 << 0)
> > -#define RIGHT_ALIGNED (1 << 1)
> > -int
> > +void
> > xbitmap_disunion(
> > - struct xbitmap *bitmap,
> > - struct xbitmap *sub)
> > + struct xbitmap *bitmap,
> > + struct xbitmap *sub)
> > {
> > - struct list_head *lp;
> > - struct xbitmap_range *br;
> > - struct xbitmap_range *new_br;
> > - struct xbitmap_range *sub_br;
> > - uint64_t sub_start;
> > - uint64_t sub_len;
> > - int state;
> > - int error = 0;
> > -
> > - if (list_empty(&bitmap->list) || list_empty(&sub->list))
> > - return 0;
> > - ASSERT(!list_empty(&sub->list));
> > -
> > - list_sort(NULL, &bitmap->list, xbitmap_range_cmp);
> > - list_sort(NULL, &sub->list, xbitmap_range_cmp);
> > -
> > - /*
> > - * Now that we've sorted both lists, we iterate bitmap once, rolling
> > - * forward through sub and/or bitmap as necessary until we find an
> > - * overlap or reach the end of either list. We do not reset lp to the
> > - * head of bitmap nor do we reset sub_br to the head of sub. The
> > - * list traversal is similar to merge sort, but we're deleting
> > - * instead. In this manner we avoid O(n^2) operations.
> > - */
> > - sub_br = list_first_entry(&sub->list, struct xbitmap_range,
> > - list);
> > - lp = bitmap->list.next;
> > - while (lp != &bitmap->list) {
> > - br = list_entry(lp, struct xbitmap_range, list);
> > -
> > - /*
> > - * Advance sub_br and/or br until we find a pair that
> > - * intersect or we run out of extents.
> > - */
> > - while (sub_br->start + sub_br->len <= br->start) {
> > - if (list_is_last(&sub_br->list, &sub->list))
> > - goto out;
> > - sub_br = list_next_entry(sub_br, list);
> > - }
> > - if (sub_br->start >= br->start + br->len) {
> > - lp = lp->next;
> > - continue;
> > - }
> > + struct interval_tree_node *itn, *n;
> >
> > - /* trim sub_br to fit the extent we have */
> > - sub_start = sub_br->start;
> > - sub_len = sub_br->len;
> > - if (sub_br->start < br->start) {
> > - sub_len -= br->start - sub_br->start;
> > - sub_start = br->start;
> > - }
> > - if (sub_len > br->len)
> > - sub_len = br->len;
> > -
> > - state = 0;
> > - if (sub_start == br->start)
> > - state |= LEFT_ALIGNED;
> > - if (sub_start + sub_len == br->start + br->len)
> > - state |= RIGHT_ALIGNED;
> > - switch (state) {
> > - case LEFT_ALIGNED:
> > - /* Coincides with only the left. */
> > - br->start += sub_len;
> > - br->len -= sub_len;
> > - break;
> > - case RIGHT_ALIGNED:
> > - /* Coincides with only the right. */
> > - br->len -= sub_len;
> > - lp = lp->next;
> > - break;
> > - case LEFT_ALIGNED | RIGHT_ALIGNED:
> > - /* Total overlap, just delete ex. */
> > - lp = lp->next;
> > - list_del(&br->list);
> > - kmem_free(br);
> > - break;
> > - case 0:
> > - /*
> > - * Deleting from the middle: add the new right extent
> > - * and then shrink the left extent.
> > - */
> > - new_br = kmem_alloc(sizeof(struct xbitmap_range),
> > - KM_MAYFAIL);
> > - if (!new_br) {
> > - error = -ENOMEM;
> > - goto out;
> > - }
> > - INIT_LIST_HEAD(&new_br->list);
> > - new_br->start = sub_start + sub_len;
> > - new_br->len = br->start + br->len - new_br->start;
> > - list_add(&new_br->list, &br->list);
> > - br->len = sub_start - br->start;
> > - lp = lp->next;
> > - break;
> > - default:
> > - ASSERT(0);
> > - break;
> > - }
> > - }
> > + if (xbitmap_empty(bitmap) || xbitmap_empty(sub))
> > + return;
> >
> > -out:
> > - return error;
> > + for_each_xbitmap_extent(itn, n, sub)
> > + __xbitmap_clear(bitmap, itn->start, itn->last);
> > }
> > -#undef LEFT_ALIGNED
> > -#undef RIGHT_ALIGNED
> >
> > /*
> > * Record all btree blocks seen while iterating all records of a btree.
> > @@ -303,14 +258,13 @@ xbitmap_set_btblocks(
> > /* How many bits are set in this bitmap? */
> > uint64_t
> > xbitmap_hweight(
> > - struct xbitmap *bitmap)
> > + struct xbitmap *bitmap)
> > {
> > - struct xbitmap_range *bmr;
> > - struct xbitmap_range *n;
> > - uint64_t ret = 0;
> > + struct interval_tree_node *itn, *n;
> > + uint64_t ret = 0;
> >
> > - for_each_xbitmap_extent(bmr, n, bitmap)
> > - ret += bmr->len;
> > + for_each_xbitmap_extent(itn, n, bitmap)
> > + ret += itn->last - itn->start + 1;
> >
> > return ret;
> > }
> > @@ -318,15 +272,15 @@ xbitmap_hweight(
> > /* Call a function for every run of set bits in this bitmap. */
> > int
> > xbitmap_iter_set(
> > - struct xbitmap *bitmap,
> > - xbitmap_walk_run_fn fn,
> > - void *priv)
> > + struct xbitmap *bitmap,
> > + xbitmap_walk_run_fn fn,
> > + void *priv)
> > {
> > - struct xbitmap_range *bex, *n;
> > - int error;
> > + struct interval_tree_node *itn, *n;
> > + int error;
> >
> > - for_each_xbitmap_extent(bex, n, bitmap) {
> > - error = fn(bex->start, bex->len, priv);
> > + for_each_xbitmap_extent(itn, n, bitmap) {
> > + error = fn(itn->start, itn->last - itn->start + 1, priv);
> > if (error)
> > break;
> > }
> > @@ -370,3 +324,11 @@ xbitmap_iter_set_bits(
> >
> > return xbitmap_iter_set(bitmap, xbitmap_walk_bits_in_run, &wb);
> > }
> > +
> > +/* Does this bitmap have no bits set at all? */
> > +bool
> > +xbitmap_empty(
> > + struct xbitmap *bitmap)
> > +{
> > + return bitmap->root.rb_root.rb_node == NULL;
> > +}
> > diff --git a/fs/xfs/scrub/bitmap.h b/fs/xfs/scrub/bitmap.h
> > index 27fde5b4a753..6be596e60ac8 100644
> > --- a/fs/xfs/scrub/bitmap.h
> > +++ b/fs/xfs/scrub/bitmap.h
> > @@ -6,21 +6,18 @@
> > #ifndef __XFS_SCRUB_BITMAP_H__
> > #define __XFS_SCRUB_BITMAP_H__
> >
> > -struct xbitmap_range {
> > - struct list_head list;
> > - uint64_t start;
> > - uint64_t len;
> > -};
> > +#include <linux/interval_tree.h>
> >
> > struct xbitmap {
> > - struct list_head list;
> > + struct rb_root_cached root;
> > };
> >
> > void xbitmap_init(struct xbitmap *bitmap);
> > void xbitmap_destroy(struct xbitmap *bitmap);
> >
> > +void xbitmap_clear(struct xbitmap *bitmap, uint64_t start, uint64_t len);
> > int xbitmap_set(struct xbitmap *bitmap, uint64_t start, uint64_t len);
> > -int xbitmap_disunion(struct xbitmap *bitmap, struct xbitmap *sub);
> > +void xbitmap_disunion(struct xbitmap *bitmap, struct xbitmap *sub);
> > int xbitmap_set_btcur_path(struct xbitmap *bitmap,
> > struct xfs_btree_cur *cur);
> > int xbitmap_set_btblocks(struct xbitmap *bitmap,
> > @@ -42,4 +39,6 @@ typedef int (*xbitmap_walk_bit_fn)(uint64_t bit, void *priv);
> > int xbitmap_iter_set_bits(struct xbitmap *bitmap, xbitmap_walk_bit_fn fn,
> > void *priv);
> >
> > +bool xbitmap_empty(struct xbitmap *bitmap);
> > +
> > #endif /* __XFS_SCRUB_BITMAP_H__ */
> >
>
