+linux-mm, linux-kernel
On Thu, Aug 17, 2017 at 6:10 PM, Shakeel Butt <[email protected]> wrote: > The fadvise() manpage is silent on fadvise()'s effect on > memory-based filesystems (shmem, hugetlbfs & ramfs) and pseudo > file systems (procfs, sysfs, kernfs). The current implementaion > of fadvise is mostly a noop for such filesystems except for > FADV_DONTNEED which will trigger expensive remote LRU cache > draining. This patch makes the noop of fadvise() on such file > systems very explicit. > > However this change has two side effects for ramfs and one for > tmpfs. First fadvise(FADV_DONTNEED) can remove the unmapped clean > zero'ed pages of ramfs (allocated through read, readahead & read > fault) and tmpfs (allocated through read fault). Also > fadvise(FADV_WILLNEED) on create such clean zero'ed pages for > ramfs. This change removes these two interfaces. > > Signed-off-by: Shakeel Butt <[email protected]> > --- > mm/fadvise.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/fadvise.c b/mm/fadvise.c > index a43013112581..702f239cd6db 100644 > --- a/mm/fadvise.c > +++ b/mm/fadvise.c > @@ -52,7 +52,9 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, > loff_t, len, int, advice) > goto out; > } > > - if (IS_DAX(inode)) { > + bdi = inode_to_bdi(mapping->host); > + > + if (IS_DAX(inode) || (bdi == &noop_backing_dev_info)) { > switch (advice) { > case POSIX_FADV_NORMAL: > case POSIX_FADV_RANDOM: > @@ -75,8 +77,6 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, > loff_t, len, int, advice) > else > endbyte--; /* inclusive */ > > - bdi = inode_to_bdi(mapping->host); > - > switch (advice) { > case POSIX_FADV_NORMAL: > f.file->f_ra.ra_pages = bdi->ra_pages; > -- > 2.14.1.480.gb18f417b89-goog >
