| Message ID | 20230629205040.665834-2-axelrasmussen@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,1/6] mm: userfaultfd: add new UFFDIO_POISON ioctl | expand |
On Thu, Jun 29, 2023 at 01:50:36PM -0700, Axel Rasmussen wrote: > At the top of `hugetlb_mfill_atomic_pte`, we need to get the folio we're > going to be mapping. There are three basic cases we're dealing with > here: > > 1. We're doing a UFFDIO_CONTINUE, in which case we lookup an existing > folio in the pagecache, instead of allocating a new one. > 2. We need to allocate a new folio. > 3. We previously failed while populating our new folio, so we "returned" > a temporary folio using `foliop` and had our caller retry. > > In a future commit I'm going to add a fourth case for UFFDIO_POISON, > where we aren't going to map a folio at all (newly allocated or > otherwise). This end state will be simpler, and we can re-use a bit more > code, if we stop using `if (...)` to distinguish the cases. > > So, refactor the cases so they share most of the same code, and instead > switch to `goto` to skip some parts depending on the case at hand. > > Signed-off-by: Axel Rasmussen <axelrasmussen@google.com> I didn't get why this patch is needed.. IIUC you added MFILL_ATOMIC_POISON handling at the entry of hugetlb_mfill_atomic_pte() anyway. Maybe it can even have its own hugetlb_mfill_atomic_poison()? Did I miss something? > --- > mm/hugetlb.c | 53 +++++++++++++++++++++++++--------------------------- > 1 file changed, 25 insertions(+), 28 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index bce28cca73a1..38711d49e4db 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6259,22 +6259,32 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, > if (IS_ERR(folio)) > goto out; > folio_in_pagecache = true; > - } else if (!*foliop) { > - /* If a folio already exists, then it's UFFDIO_COPY for > - * a non-missing case. Return -EEXIST. > - */ > - if (vm_shared && > - hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) { > - ret = -EEXIST; > - goto out; > + goto ready; > + } > + > + /* If a folio already exists, then it's UFFDIO_COPY for > + * a non-missing case. Return -EEXIST. > + */ > + if (vm_shared && hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) { > + ret = -EEXIST; > + if (*foliop) { > + folio_put(*foliop); > + *foliop = NULL; > } > + goto out; > + } > > - folio = alloc_hugetlb_folio(dst_vma, dst_addr, 0); > - if (IS_ERR(folio)) { > - ret = -ENOMEM; > - goto out; > + folio = alloc_hugetlb_folio(dst_vma, dst_addr, 0); > + if (IS_ERR(folio)) { > + ret = -ENOMEM; > + if (*foliop) { > + folio_put(*foliop); > + *foliop = NULL; > } > + goto out; > + } > > + if (!*foliop) { > ret = copy_folio_from_user(folio, (const void __user *) src_addr, > false); > > @@ -6302,22 +6312,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, > */ > goto out; > } > - } else { > - if (vm_shared && > - hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) { > - folio_put(*foliop); > - ret = -EEXIST; > - *foliop = NULL; > - goto out; > - } > - > - folio = alloc_hugetlb_folio(dst_vma, dst_addr, 0); > - if (IS_ERR(folio)) { > - folio_put(*foliop); > - ret = -ENOMEM; > - *foliop = NULL; > - goto out; > - } > + } else { /* Caller retried because we set *foliop previously */ > ret = copy_user_large_folio(folio, *foliop, dst_addr, dst_vma); > folio_put(*foliop); > *foliop = NULL; > @@ -6327,6 +6322,8 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, > } > } > > +ready: /* `folio` ready to map (non-NULL, populated) */ > + > /* > * The memory barrier inside __folio_mark_uptodate makes sure that > * preceding stores to the page contents become visible before > -- > 2.41.0.255.g8b1d071c50-goog >
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index bce28cca73a1..38711d49e4db 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6259,22 +6259,32 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, if (IS_ERR(folio)) goto out; folio_in_pagecache = true; - } else if (!*foliop) { - /* If a folio already exists, then it's UFFDIO_COPY for - * a non-missing case. Return -EEXIST. - */ - if (vm_shared && - hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) { - ret = -EEXIST; - goto out; + goto ready; + } + + /* If a folio already exists, then it's UFFDIO_COPY for + * a non-missing case. Return -EEXIST. + */ + if (vm_shared && hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) { + ret = -EEXIST; + if (*foliop) { + folio_put(*foliop); + *foliop = NULL; } + goto out; + } - folio = alloc_hugetlb_folio(dst_vma, dst_addr, 0); - if (IS_ERR(folio)) { - ret = -ENOMEM; - goto out; + folio = alloc_hugetlb_folio(dst_vma, dst_addr, 0); + if (IS_ERR(folio)) { + ret = -ENOMEM; + if (*foliop) { + folio_put(*foliop); + *foliop = NULL; } + goto out; + } + if (!*foliop) { ret = copy_folio_from_user(folio, (const void __user *) src_addr, false); @@ -6302,22 +6312,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, */ goto out; } - } else { - if (vm_shared && - hugetlbfs_pagecache_present(h, dst_vma, dst_addr)) { - folio_put(*foliop); - ret = -EEXIST; - *foliop = NULL; - goto out; - } - - folio = alloc_hugetlb_folio(dst_vma, dst_addr, 0); - if (IS_ERR(folio)) { - folio_put(*foliop); - ret = -ENOMEM; - *foliop = NULL; - goto out; - } + } else { /* Caller retried because we set *foliop previously */ ret = copy_user_large_folio(folio, *foliop, dst_addr, dst_vma); folio_put(*foliop); *foliop = NULL; @@ -6327,6 +6322,8 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte, } } +ready: /* `folio` ready to map (non-NULL, populated) */ + /* * The memory barrier inside __folio_mark_uptodate makes sure that * preceding stores to the page contents become visible before
At the top of `hugetlb_mfill_atomic_pte`, we need to get the folio we're going to be mapping. There are three basic cases we're dealing with here: 1. We're doing a UFFDIO_CONTINUE, in which case we lookup an existing folio in the pagecache, instead of allocating a new one. 2. We need to allocate a new folio. 3. We previously failed while populating our new folio, so we "returned" a temporary folio using `foliop` and had our caller retry. In a future commit I'm going to add a fourth case for UFFDIO_POISON, where we aren't going to map a folio at all (newly allocated or otherwise). This end state will be simpler, and we can re-use a bit more code, if we stop using `if (...)` to distinguish the cases. So, refactor the cases so they share most of the same code, and instead switch to `goto` to skip some parts depending on the case at hand. Signed-off-by: Axel Rasmussen <axelrasmussen@google.com> --- mm/hugetlb.c | 53 +++++++++++++++++++++++++--------------------------- 1 file changed, 25 insertions(+), 28 deletions(-)