| Message ID | alpine.LSU.2.11.1811261522040.2275@eggly.anvils (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | huge_memory,khugepaged tmpfs split/collapse fixes | expand |
On Mon, Nov 26, 2018 at 03:23:37PM -0800, Hugh Dickins wrote: > Huge tmpfs testing showed that although collapse_shmem() recognizes a > concurrently truncated or hole-punched page correctly, its handling of > holes was liable to refill an emptied extent. Add check to stop that. > > Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages") > Signed-off-by: Hugh Dickins <hughd@google.com> > Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Cc: stable@vger.kernel.org # 4.8+ I'm not yet comfortable with XArray API. Matthew, what is your take on the patch? > --- > mm/khugepaged.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index c13625c1ad5e..2070c316f06e 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1359,6 +1359,17 @@ static void collapse_shmem(struct mm_struct *mm, > > VM_BUG_ON(index != xas.xa_index); > if (!page) { > + /* > + * Stop if extent has been truncated or hole-punched, > + * and is now completely empty. > + */ > + if (index == start) { > + if (!xas_next_entry(&xas, end - 1)) { > + result = SCAN_TRUNCATED; > + break; > + } > + xas_set(&xas, index); > + } > if (!shmem_charge(mapping->host, 1)) { > result = SCAN_FAIL; > break; > -- > 2.20.0.rc0.387.gc7a69e6b6c-goog >
On Mon, Nov 26, 2018 at 03:23:37PM -0800, Hugh Dickins wrote: > VM_BUG_ON(index != xas.xa_index); > if (!page) { > + /* > + * Stop if extent has been truncated or hole-punched, > + * and is now completely empty. > + */ > + if (index == start) { > + if (!xas_next_entry(&xas, end - 1)) { > + result = SCAN_TRUNCATED; > + break; > + } > + xas_set(&xas, index); > + } > if (!shmem_charge(mapping->host, 1)) { Reviewed-by: Matthew Wilcox <willy@infradead.org> I'd use xas_find() directly here; I don't think it warrants the inlined version of xas_next_entry(). But I'm happy either way.
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index c13625c1ad5e..2070c316f06e 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1359,6 +1359,17 @@ static void collapse_shmem(struct mm_struct *mm, VM_BUG_ON(index != xas.xa_index); if (!page) { + /* + * Stop if extent has been truncated or hole-punched, + * and is now completely empty. + */ + if (index == start) { + if (!xas_next_entry(&xas, end - 1)) { + result = SCAN_TRUNCATED; + break; + } + xas_set(&xas, index); + } if (!shmem_charge(mapping->host, 1)) { result = SCAN_FAIL; break;
Huge tmpfs testing showed that although collapse_shmem() recognizes a concurrently truncated or hole-punched page correctly, its handling of holes was liable to refill an emptied extent. Add check to stop that. Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages") Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: stable@vger.kernel.org # 4.8+ --- mm/khugepaged.c | 11 +++++++++++ 1 file changed, 11 insertions(+)