From: Ackerley Tng <[email protected]> Provide a function to check that a range has given attributes.
Optimize setting memory attributes by returning early if all pages in the requested range already have the requested attributes. Reviewed-by: Fuad Tabba <[email protected]> Tested-by: Shivank Garg <[email protected]> Reviewed-by: Binbin Wu <[email protected]> Reviewed-by: Xiaoyao Li <[email protected]> Signed-off-by: Ackerley Tng <[email protected]> --- virt/kvm/guest_memfd.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index d14a7024bdc7b..ac8e0c6d6e942 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -98,6 +98,24 @@ static bool kvm_gmem_is_shared_mem(struct inode *inode, pgoff_t index) return !kvm_gmem_is_private_mem(inode, index); } +static bool kvm_gmem_range_has_attributes(struct inode *inode, + pgoff_t index, size_t nr_pages, + u64 attributes) +{ + struct maple_tree *mt = &GMEM_I(inode)->attributes; + pgoff_t end = index + nr_pages - 1; + void *entry; + + lockdep_assert(mt_lock_is_held(mt)); + + mt_for_each(mt, entry, index, end) { + if (kvm_gmem_get_attributes(inode, entry) != attributes) + return false; + } + + return true; +} + /* * Returns a locked folio on success. The caller is responsible for * setting the up-to-date flag before the memory is mapped into the guest. @@ -623,12 +641,15 @@ static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start, pgoff_t end = start + nr_pages; struct maple_tree *mt; struct ma_state mas; - int r; + int r = 0; mt = &gi->attributes; filemap_invalidate_lock(mapping); + if (kvm_gmem_range_has_attributes(inode, start, nr_pages, attrs)) + goto out; + mas_init(&mas, mt, start); r = kvm_gmem_mas_preallocate(&mas, attrs, start, nr_pages); if (r) { -- 2.55.0.897.gb25b4bd76c-goog
