On Tue, Mar 22, 2022 at 02:46:48PM -0700, Andrew Morton wrote:
From: Charan Teja Kalla quic_charante@quicinc.com Subject: mm: madvise: skip unmapped vma holes passed to process_madvise
The process_madvise() system call is expected to skip holes in vma passed through 'struct iovec' vector list. But do_madvise, which process_madvise() calls for each vma, returns ENOMEM in case of unmapped holes, despite the VMA is processed.
Thus process_madvise() should treat ENOMEM as expected and consider the VMA passed to as processed and continue processing other vma's in the vector list. Returning -ENOMEM to user, despite the VMA is processed, will be unable to figure out where to start the next madvise.
Link: https://lkml.kernel.org/r/4f091776142f2ebf7b94018146de72318474e686.164700875...
I thought it was still under discussion and Charan will post next version along with previous patch "mm: madvise: return correct bytes advised with process_madvise"
https://lore.kernel.org/linux-mm/7207b2f5-6b3e-aea4-aa1b-9c6d849abe34@quicin...
Fixes: ecb8ac8b1f14("mm/madvise: introduce process_madvise() syscall: an external memory hinting API") Signed-off-by: Charan Teja Kalla quic_charante@quicinc.com Cc: David Rientjes rientjes@google.com Cc: Michal Hocko mhocko@suse.com Cc: Minchan Kim minchan@kernel.org Cc: Nadav Amit nadav.amit@gmail.com Cc: Stephen Rothwell sfr@canb.auug.org.au Cc: Suren Baghdasaryan surenb@google.com Cc: Vlastimil Babka vbabka@suse.cz Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org
mm/madvise.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
--- a/mm/madvise.c~mm-madvise-skip-unmapped-vma-holes-passed-to-process_madvise +++ a/mm/madvise.c @@ -1428,9 +1428,16 @@ SYSCALL_DEFINE5(process_madvise, int, pi while (iov_iter_count(&iter)) { iovec = iov_iter_iovec(&iter);
/** do_madvise returns ENOMEM if unmapped holes are present* in the passed VMA. process_madvise() is expected to skip* unmapped holes passed to it in the 'struct iovec' list* and not fail because of them. Thus treat -ENOMEM return* from do_madvise as valid and continue processing.*/
if (ret < 0)
if (ret < 0 && ret != -ENOMEM) break;_