[PATCH 19/20] xfs: convert xfarray_pagesort to deal with large folios

Christoph Hellwig
2024-01-29T14:36:15Z

From: "Darrick J. Wong" <djwong@kernel.org>

Convert xfarray_pagesort to handle large folios by introducing a new
xfile_get_folio routine that can return a folio of arbitrary size, and
using heapsort on the full folio. This also corrects an off-by-one bug
in the calculation of len in xfarray_pagesort that was papered over by
xfarray_want_pagesort.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev>
---
fs/xfs/scrub/trace.h | 43 ++++++++-
fs/xfs/scrub/xfarray.c | 201 +++++++++++++++++++----------------------
fs/xfs/scrub/xfarray.h | 10 +-
3 files changed, 143 insertions(+), 111 deletions(-)

diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index c61fa7a95ef522..3a1a827828dcb9 100644
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -956,7 +956,7 @@ TRACE_EVENT(xfarray_isort,
__entry->hi - __entry->lo)
);

-TRACE_EVENT(xfarray_pagesort,
+TRACE_EVENT(xfarray_foliosort,
TP_PROTO(struct xfarray_sortinfo *si, uint64_t lo, uint64_t hi),
TP_ARGS(si, lo, hi),
TP_STRUCT__entry(
@@ -1027,6 +1027,47 @@ TRACE_EVENT(xfarray_sort,
__entry->bytes)
);

+TRACE_EVENT(xfarray_sort_scan,
+ TP_PROTO(struct xfarray_sortinfo *si, unsigned long long idx),
+ TP_ARGS(si, idx),
+ TP_STRUCT__entry(
+ __field(unsigned long, ino)
+ __field(unsigned long long, nr)
+ __field(size_t, obj_size)
+ __field(unsigned long long, idx)
+ __field(unsigned long long, folio_pos)
+ __field(unsigned long, folio_bytes)
+ __field(unsigned long long, first_idx)
+ __field(unsigned long long, last_idx)
+ ),
+ TP_fast_assign(
+ __entry->nr = si->array->nr;
+ __entry->obj_size = si->array->obj_size;
+ __entry->ino = file_inode(si->array->xfile->file)->i_ino;
+ __entry->idx = idx;
+ if (si->folio) {
+ __entry->folio_pos = folio_pos(si->folio);
+ __entry->folio_bytes = folio_size(si->folio);
+ __entry->first_idx = si->first_folio_idx;
+ __entry->last_idx = si->last_folio_idx;
+ } else {
+ __entry->folio_pos = 0;
+ __entry->folio_bytes = 0;
+ __entry->first_idx = 0;
+ __entry->last_idx = 0;
+ }
+ ),
+ TP_printk("xfino 0x%lx nr %llu objsz %zu idx %llu folio_pos 0x%llx folio_bytes 0x%lx first_idx %llu last_idx %llu",
+ __entry->ino,
+ __entry->nr,
+ __entry->obj_size,
+ __entry->idx,
+ __entry->folio_pos,
+ __entry->folio_bytes,
+ __entry->first_idx,
+ __entry->last_idx)
+);
+
TRACE_EVENT(xfarray_sort_stats,
TP_PROTO(struct xfarray_sortinfo *si, int error),
TP_ARGS(si, error),
diff --git a/fs/xfs/scrub/xfarray.c b/fs/xfs/scrub/xfarray.c
index 379e1db22269c7..17c982a4821d47 100644
--- a/fs/xfs/scrub/xfarray.c
+++ b/fs/xfs/scrub/xfarray.c
@@ -563,70 +563,42 @@ xfarray_isort(
return xfile_store(si->array->xfile, scratch, len, lo_pos);
}

-/* Grab a page for sorting records. */
-static inline int
-xfarray_sort_get_page(
- struct xfarray_sortinfo *si,
- loff_t pos,
- uint64_t len)
-{
- return xfile_get_page(si->array->xfile, pos, len, &si->xfpage);
-}
-
-/* Release a page we grabbed for sorting records. */
-static inline int
-xfarray_sort_put_page(
- struct xfarray_sortinfo *si)
-{
- if (!xfile_page_cached(&si->xfpage))
- return 0;
- return xfile_put_page(si->array->xfile, &si->xfpage);
-}
-
-/* Decide if these records are eligible for in-page sorting. */
-static inline bool
-xfarray_want_pagesort(
- struct xfarray_sortinfo *si,
- xfarray_idx_t lo,
- xfarray_idx_t hi)
-{
- pgoff_t lo_page;
- pgoff_t hi_page;
- loff_t end_pos;
-
- /* We can only map one page at a time. */
- lo_page = xfarray_pos(si->array, lo) >> PAGE_SHIFT;
- end_pos = xfarray_pos(si->array, hi) + si->array->obj_size - 1;
- hi_page = end_pos >> PAGE_SHIFT;
-
- return lo_page == hi_page;
-}
-
-/* Sort a bunch of records that all live in the same memory page. */
+/*
+ * Sort the records from lo to hi (inclusive) if they are all backed by the
+ * same memory folio. Returns 1 if it sorted, 0 if it did not, or a negative
+ * errno.
+ */
STATIC int
-xfarray_pagesort(
+xfarray_foliosort(
struct xfarray_sortinfo *si,
xfarray_idx_t lo,
xfarray_idx_t hi)
{
+ struct folio *folio;
void *startp;
loff_t lo_pos = xfarray_pos(si->array, lo);
- uint64_t len = xfarray_pos(si->array, hi - lo);
- int error = 0;
+ uint64_t len = xfarray_pos(si->array, hi - lo + 1);

- trace_xfarray_pagesort(si, lo, hi);
+ /* No single folio could back this many records. */
+ if (len > XFILE_MAX_FOLIO_SIZE)
+ return 0;

xfarray_sort_bump_loads(si);
- error = xfarray_sort_get_page(si, lo_pos, len);
- if (error)
- return error;
+ folio = xfile_get_folio(si->array->xfile, lo_pos, len, XFILE_ALLOC);
+ if (IS_ERR(folio))
+ return PTR_ERR(folio);
+ if (!folio)
+ return 0;
+
+ trace_xfarray_foliosort(si, lo, hi);

xfarray_sort_bump_heapsorts(si);
- startp = page_address(si->xfpage.page) + offset_in_page(lo_pos);
+ startp = folio_address(folio) + offset_in_folio(folio, lo_pos);
sort(startp, hi - lo + 1, si->array->obj_size, si->cmp_fn, NULL);

xfarray_sort_bump_stores(si);
- return xfarray_sort_put_page(si);
+ xfile_put_folio(si->array->xfile, folio);
+ return 1;
}

/* Return a pointer to the xfarray pivot record within the sortinfo struct. */
@@ -814,63 +786,78 @@ xfarray_qsort_push(
return 0;
}

+static inline void
+xfarray_sort_scan_done(
+ struct xfarray_sortinfo *si)
+{
+ if (si->folio)
+ xfile_put_folio(si->array->xfile, si->folio);
+ si->folio = NULL;
+}
+
/*
- * Load an element from the array into the first scratchpad and cache the page,
- * if possible.
+ * Cache the folio backing the start of the given array element. If the array
+ * element is contained entirely within the folio, return a pointer to the
+ * cached folio. Otherwise, load the element into the scratchpad and return a
+ * pointer to the scratchpad.
*/
static inline int
-xfarray_sort_load_cached(
+xfarray_sort_scan(
struct xfarray_sortinfo *si,
xfarray_idx_t idx,
- void *ptr)
+ void **ptrp)
{
loff_t idx_pos = xfarray_pos(si->array, idx);
- pgoff_t startpage;
- pgoff_t endpage;
int error = 0;

- /*
- * If this load would split a page, release the cached page, if any,
- * and perform a traditional read.
- */
- startpage = idx_pos >> PAGE_SHIFT;
- endpage = (idx_pos + si->array->obj_size - 1) >> PAGE_SHIFT;
- if (startpage != endpage) {
- error = xfarray_sort_put_page(si);
- if (error)
- return error;
+ if (xfarray_sort_terminated(si, &error))
+ return error;

- if (xfarray_sort_terminated(si, &error))
- return error;
+ trace_xfarray_sort_scan(si, idx);

- return xfile_load(si->array->xfile, ptr,
- si->array->obj_size, idx_pos);
- }
+ /* If the cached folio doesn't cover this index, release it. */
+ if (si->folio &&
+ (idx < si->first_folio_idx || idx > si->last_folio_idx))
+ xfarray_sort_scan_done(si);

- /* If the cached page is not the one we want, release it. */
- if (xfile_page_cached(&si->xfpage) &&
- xfile_page_index(&si->xfpage) != startpage) {
- error = xfarray_sort_put_page(si);
- if (error)
- return error;
+ /* Grab the first folio that backs this array element. */
+ if (!si->folio) {
+ loff_t next_pos;
+
+ si->folio = xfile_get_folio(si->array->xfile, idx_pos,
+ si->array->obj_size, XFILE_ALLOC);
+ if (IS_ERR(si->folio))
+ return PTR_ERR(si->folio);
+
+ si->first_folio_idx = xfarray_idx(si->array,
+ folio_pos(si->folio) + si->array->obj_size - 1);
+
+ next_pos = folio_pos(si->folio) + folio_size(si->folio);
+ si->last_folio_idx = xfarray_idx(si->array, next_pos - 1);
+ if (xfarray_pos(si->array, si->last_folio_idx + 1) > next_pos)
+ si->last_folio_idx--;
+
+ trace_xfarray_sort_scan(si, idx);
}

/*
- * If we don't have a cached page (and we know the load is contained
- * in a single page) then grab it.
+ * If this folio still doesn't cover the desired element, it must cross
+ * a folio boundary. Read into the scratchpad and we're done.
*/
- if (!xfile_page_cached(&si->xfpage)) {
- if (xfarray_sort_terminated(si, &error))
- return error;
+ if (idx < si->first_folio_idx || idx > si->last_folio_idx) {
+ void *temp = xfarray_scratch(si->array);

- error = xfarray_sort_get_page(si, startpage << PAGE_SHIFT,
- PAGE_SIZE);
+ error = xfile_load(si->array->xfile, temp, si->array->obj_size,
+ idx_pos);
if (error)
return error;
+
+ *ptrp = temp;
+ return 0;
}

- memcpy(ptr, page_address(si->xfpage.page) + offset_in_page(idx_pos),
- si->array->obj_size);
+ /* Otherwise return a pointer to the array element in the folio. */
+ *ptrp = folio_address(si->folio) + offset_in_folio(si->folio, idx_pos);
return 0;
}

@@ -937,6 +924,8 @@ xfarray_sort(
pivot = xfarray_sortinfo_pivot(si);

while (si->stack_depth >= 0) {
+ int ret;
+
lo = si_lo[si->stack_depth];
hi = si_hi[si->stack_depth];

@@ -949,13 +938,13 @@ xfarray_sort(
}

/*
- * If directly mapping the page and sorting can solve our
+ * If directly mapping the folio and sorting can solve our
* problems, we're done.
*/
- if (xfarray_want_pagesort(si, lo, hi)) {
- error = xfarray_pagesort(si, lo, hi);
- if (error)
- goto out_free;
+ ret = xfarray_foliosort(si, lo, hi);
+ if (ret < 0)
+ goto out_free;
+ if (ret == 1) {
si->stack_depth--;
continue;
}
@@ -980,25 +969,24 @@ xfarray_sort(
* than the pivot is on the right side of the range.
*/
while (lo < hi) {
+ void *p;
+
/*
* Decrement hi until it finds an a[hi] less than the
* pivot value.
*/
- error = xfarray_sort_load_cached(si, hi, scratch);
+ error = xfarray_sort_scan(si, hi, &p);
if (error)
goto out_free;
- while (xfarray_sort_cmp(si, scratch, pivot) >= 0 &&
- lo < hi) {
+ while (xfarray_sort_cmp(si, p, pivot) >= 0 && lo < hi) {
hi--;
- error = xfarray_sort_load_cached(si, hi,
- scratch);
+ error = xfarray_sort_scan(si, hi, &p);
if (error)
goto out_free;
}
- error = xfarray_sort_put_page(si);
- if (error)
- goto out_free;
-
+ if (p != scratch)
+ memcpy(scratch, p, si->array->obj_size);
+ xfarray_sort_scan_done(si);
if (xfarray_sort_terminated(si, &error))
goto out_free;

@@ -1013,21 +1001,18 @@ xfarray_sort(
* Increment lo until it finds an a[lo] greater than
* the pivot value.
*/
- error = xfarray_sort_load_cached(si, lo, scratch);
+ error = xfarray_sort_scan(si, lo, &p);
if (error)
goto out_free;
- while (xfarray_sort_cmp(si, scratch, pivot) <= 0 &&
- lo < hi) {
+ while (xfarray_sort_cmp(si, p, pivot) <= 0 && lo < hi) {
lo++;
- error = xfarray_sort_load_cached(si, lo,
- scratch);
+ error = xfarray_sort_scan(si, lo, &p);
if (error)
goto out_free;
}
- error = xfarray_sort_put_page(si);
- if (error)
- goto out_free;
-
+ if (p != scratch)
+ memcpy(scratch, p, si->array->obj_size);
+ xfarray_sort_scan_done(si);
if (xfarray_sort_terminated(si, &error))
goto out_free;

diff --git a/fs/xfs/scrub/xfarray.h b/fs/xfs/scrub/xfarray.h
index 6f2862054e194d..ec643cc9fc1432 100644
--- a/fs/xfs/scrub/xfarray.h
+++ b/fs/xfs/scrub/xfarray.h
@@ -105,8 +105,14 @@ struct xfarray_sortinfo {
/* XFARRAY_SORT_* flags; see below. */
unsigned int flags;

- /* Cache a page here for faster access. */
- struct xfile_page xfpage;
+ /* Cache a folio here for faster scanning for pivots */
+ struct folio *folio;
+
+ /* First array index in folio that is completely readable */
+ xfarray_idx_t first_folio_idx;
+
+ /* Last array index in folio that is completely readable */
+ xfarray_idx_t last_folio_idx;

#ifdef DEBUG
/* Performance statistics. */
--
2.39.2