Lightweight guard region support has been extended in Linux 6.15, permitting the use of these features for file-backed and read-only mappings. Update the description for these operations in the madvise manpage to describe the changed behaviour. --- man/man2/madvise.2 | 37 +++++++++++++++++++++++++++---------- 1 file changed, 27 insertions(+), 10 deletions(-) diff --git a/man/man2/madvise.2 b/man/man2/madvise.2 index bd2b90b7a..37492c8cf 100644 --- a/man/man2/madvise.2 +++ b/man/man2/madvise.2 @@ -697,9 +697,22 @@ is applied to regions containing pre-existing lightweight guard regions, they are left in place. .IP -This operation is supported -only for writable anonymous private mappings -which have not been mlock'd. +Prior to Linux v6.15 This operation was supported +only for writable anonymous private mappings. +Since Linux v6.15 both anonymous and file-backed +mappings are supported, including read-only mappings. +.IP +The mapping must not be mlock'd, +nor can they map hugetlb ranges +or special mappings +for example, +mappings marked with kernel-internal flags such as +.B VM_PFNMAP +or +.BR VM_IO , +or secret memory regions created using +.BR memfd_secret(2) . +.IP An .B EINVAL error is returned if it is attempted on any other kind of mapping. @@ -756,19 +769,23 @@ and .IP All mappings in the range other than lightweight guard regions -are left in place -(including mlock'd mappings). -The operation is, -however, -valid only for writable anonymous private mappings, +are left in place. +The operation is supported on those mappings +permitted by +.B MADV_GUARD_INSTALL +in addition to mlock()'d mappings, returning an .B EINVAL error otherwise. .IP When lightweight guard regions are removed, they act as empty regions of the containing mapping. -Since only writable anonymous private mappings are supported, -they therefore become zero-fill-on-demand pages. +Anonymous private mappings therefore become +zero-fill-on-demand pages, +and file-backed mappings are repopulating with the +memory contents from the up-to-date contents of the +underlying mapped file. + .IP If any transparent huge pages are encountered in the operation, they are left in place. -- 2.48.1
