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mm/filemap: reduce unnecessary xarray lookups in filemap_get_folios_contig()

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Apply the same optimization used in filemap_get_read_batch() by moving the
boundary check from the loop condition to before xas_next(), avoiding an
unnecessary xarray lookup and reducing branches in the fast path.

Link: https://lore.kernel.org/20260620062446.351475-3-chizhiling@163.com
Signed-off-by: Chi Zhiling <chizhiling@kylinos.cn>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Chi Zhiling
2026-06-20 14:24:46 +08:00
committed by Andrew Morton
parent e1c345582c
commit 32cd1afeca
1 changed files with 14 additions and 15 deletions
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29
mm/filemap.c
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@@ -2270,10 +2270,11 @@ unsigned filemap_get_folios_contig(struct address_space *mapping,
unsigned long nr;
struct folio *folio;
rcu_read_lock();
if (*start > end)
return 0;
for (folio = xas_load(&xas); folio && xas.xa_index <= end;
folio = xas_next(&xas)) {
rcu_read_lock();
for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) {
if (xas_retry(&xas, folio))
continue;
/*
@@ -2281,11 +2282,11 @@ unsigned filemap_get_folios_contig(struct address_space *mapping,
* No current caller is looking for DAX entries.
*/
if (xa_is_value(folio))
goto update_start;
break;
/* If we landed in the middle of a THP, continue at its end. */
if (xa_is_sibling(folio))
goto update_start;
break;
if (!folio_try_get(folio))
goto retry;
@@ -2293,29 +2294,27 @@ unsigned filemap_get_folios_contig(struct address_space *mapping,
if (unlikely(folio != xas_reload(&xas)))
goto put_folio;
if (!folio_batch_add(fbatch, folio)) {
*start = folio_next_index(folio);
goto out;
}
if (!folio_batch_add(fbatch, folio))
break;
xas_advance(&xas, folio_next_index(folio) - 1);
if (xas.xa_index >= end)
break;
continue;
put_folio:
folio_put(folio);
retry:
xas_reset(&xas);
}
rcu_read_unlock();
update_start:
nr = folio_batch_count(fbatch);
if (nr) {
folio = fbatch->folios[nr - 1];
*start = folio_next_index(folio);
}
out:
rcu_read_unlock();
return folio_batch_count(fbatch);
return nr;
}
EXPORT_SYMBOL(filemap_get_folios_contig);