| Message ID | 20210503180737.2487560-7-axelrasmussen@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | userfaultfd: add minor fault handling for shmem | expand |
Axel, On Mon, May 03, 2021 at 11:07:33AM -0700, Axel Rasmussen wrote: > In a previous commit, we added the mfill_atomic_install_pte() helper. > This helper does the job of setting up PTEs for an existing page, to map > it into a given VMA. It deals with both the anon and shmem cases, as > well as the shared and private cases. > > In other words, shmem_mfill_atomic_pte() duplicates a case it already > handles. So, expose it, and let shmem_mfill_atomic_pte() use it > directly, to reduce code duplication. > > This requires that we refactor shmem_mfill_atomic_pte() a bit: > > Instead of doing accounting (shmem_recalc_inode() et al) part-way > through the PTE setup, do it afterward. This frees up > mfill_atomic_install_pte() from having to care about this accounting, > and means we don't need to e.g. shmem_uncharge() in the error path. > > A side effect is this switches shmem_mfill_atomic_pte() to use > lru_cache_add_inactive_or_unevictable() instead of just lru_cache_add(). > This wrapper does some extra accounting in an exceptional case, if > appropriate, so it's actually the more correct thing to use. > > Signed-off-by: Axel Rasmussen <axelrasmussen@google.com> (The moving of "ret = -ENOMEM" seems unnecessary, but not a big deal I think) Reviewed-by: Peter Xu <peterx@redhat.com> Thanks,
On Mon, 3 May 2021, Axel Rasmussen wrote: > In a previous commit, we added the mfill_atomic_install_pte() helper. > This helper does the job of setting up PTEs for an existing page, to map > it into a given VMA. It deals with both the anon and shmem cases, as > well as the shared and private cases. > > In other words, shmem_mfill_atomic_pte() duplicates a case it already > handles. So, expose it, and let shmem_mfill_atomic_pte() use it > directly, to reduce code duplication. > > This requires that we refactor shmem_mfill_atomic_pte() a bit: > > Instead of doing accounting (shmem_recalc_inode() et al) part-way > through the PTE setup, do it afterward. This frees up > mfill_atomic_install_pte() from having to care about this accounting, > and means we don't need to e.g. shmem_uncharge() in the error path. > > A side effect is this switches shmem_mfill_atomic_pte() to use > lru_cache_add_inactive_or_unevictable() instead of just lru_cache_add(). > This wrapper does some extra accounting in an exceptional case, if > appropriate, so it's actually the more correct thing to use. > > Signed-off-by: Axel Rasmussen <axelrasmussen@google.com> Acked-by: Hugh Dickins <hughd@google.com> And thanks for doing those late mcopy->mfill renamings, I think those represent Andrea's intent better. As far as I'm concerned, this series is now ripe for picking into mmotm (bearing in mind the dependencies you noted in 00/10): thank you Axel. > --- > include/linux/userfaultfd_k.h | 5 +++ > mm/shmem.c | 58 ++++++++--------------------------- > mm/userfaultfd.c | 17 ++++------ > 3 files changed, 23 insertions(+), 57 deletions(-) > > diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h > index 794d1538b8ba..331d2ccf0bcc 100644 > --- a/include/linux/userfaultfd_k.h > +++ b/include/linux/userfaultfd_k.h > @@ -53,6 +53,11 @@ enum mcopy_atomic_mode { > MCOPY_ATOMIC_CONTINUE, > }; > > +extern int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, > + struct vm_area_struct *dst_vma, > + unsigned long dst_addr, struct page *page, > + bool newly_allocated, bool wp_copy); > + > extern ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start, > unsigned long src_start, unsigned long len, > bool *mmap_changing, __u64 mode); > diff --git a/mm/shmem.c b/mm/shmem.c > index e361f1d81c8d..2e9f56c83489 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -2378,14 +2378,11 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, > struct address_space *mapping = inode->i_mapping; > gfp_t gfp = mapping_gfp_mask(mapping); > pgoff_t pgoff = linear_page_index(dst_vma, dst_addr); > - spinlock_t *ptl; > void *page_kaddr; > struct page *page; > - pte_t _dst_pte, *dst_pte; > int ret; > pgoff_t max_off; > > - ret = -ENOMEM; > if (!shmem_inode_acct_block(inode, 1)) { > /* > * We may have got a page, returned -ENOENT triggering a retry, > @@ -2396,10 +2393,11 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, > put_page(*pagep); > *pagep = NULL; > } > - goto out; > + return -ENOMEM; > } > > if (!*pagep) { > + ret = -ENOMEM; > page = shmem_alloc_page(gfp, info, pgoff); > if (!page) > goto out_unacct_blocks; > @@ -2414,9 +2412,9 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, > /* fallback to copy_from_user outside mmap_lock */ > if (unlikely(ret)) { > *pagep = page; > - shmem_inode_unacct_blocks(inode, 1); > + ret = -ENOENT; > /* don't free the page */ > - return -ENOENT; > + goto out_unacct_blocks; > } > } else { /* ZEROPAGE */ > clear_highpage(page); > @@ -2442,32 +2440,10 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, > if (ret) > goto out_release; > > - _dst_pte = mk_pte(page, dst_vma->vm_page_prot); > - if (dst_vma->vm_flags & VM_WRITE) > - _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte)); > - else { > - /* > - * We don't set the pte dirty if the vma has no > - * VM_WRITE permission, so mark the page dirty or it > - * could be freed from under us. We could do it > - * unconditionally before unlock_page(), but doing it > - * only if VM_WRITE is not set is faster. > - */ > - set_page_dirty(page); > - } > - > - dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); > - > - ret = -EFAULT; > - max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); > - if (unlikely(pgoff >= max_off)) > - goto out_release_unlock; > - > - ret = -EEXIST; > - if (!pte_none(*dst_pte)) > - goto out_release_unlock; > - > - lru_cache_add(page); > + ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr, > + page, true, false); > + if (ret) > + goto out_delete_from_cache; > > spin_lock_irq(&info->lock); > info->alloced++; > @@ -2475,27 +2451,17 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, > shmem_recalc_inode(inode); > spin_unlock_irq(&info->lock); > > - inc_mm_counter(dst_mm, mm_counter_file(page)); > - page_add_file_rmap(page, false); > - set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); > - > - /* No need to invalidate - it was non-present before */ > - update_mmu_cache(dst_vma, dst_addr, dst_pte); > - pte_unmap_unlock(dst_pte, ptl); > + SetPageDirty(page); > unlock_page(page); > - ret = 0; > -out: > - return ret; > -out_release_unlock: > - pte_unmap_unlock(dst_pte, ptl); > - ClearPageDirty(page); > + return 0; > +out_delete_from_cache: > delete_from_page_cache(page); > out_release: > unlock_page(page); > put_page(page); > out_unacct_blocks: > shmem_inode_unacct_blocks(inode, 1); > - goto out; > + return ret; > } > #endif /* CONFIG_USERFAULTFD */ > > diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c > index d1ac73a0d2a9..5508f7d9e2dc 100644 > --- a/mm/userfaultfd.c > +++ b/mm/userfaultfd.c > @@ -51,18 +51,13 @@ struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, > /* > * Install PTEs, to map dst_addr (within dst_vma) to page. > * > - * This function handles MCOPY_ATOMIC_CONTINUE (which is always file-backed), > - * whether or not dst_vma is VM_SHARED. It also handles the more general > - * MCOPY_ATOMIC_NORMAL case, when dst_vma is *not* VM_SHARED (it may be file > - * backed, or not). > - * > - * Note that MCOPY_ATOMIC_NORMAL for a VM_SHARED dst_vma is handled by > - * shmem_mcopy_atomic_pte instead. > + * This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem > + * and anon, and for both shared and private VMAs. > */ > -static int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, > - struct vm_area_struct *dst_vma, > - unsigned long dst_addr, struct page *page, > - bool newly_allocated, bool wp_copy) > +int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, > + struct vm_area_struct *dst_vma, > + unsigned long dst_addr, struct page *page, > + bool newly_allocated, bool wp_copy) > { > int ret; > pte_t _dst_pte, *dst_pte; > -- > 2.31.1.527.g47e6f16901-goog > >
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 794d1538b8ba..331d2ccf0bcc 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -53,6 +53,11 @@ enum mcopy_atomic_mode { MCOPY_ATOMIC_CONTINUE, }; +extern int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, + struct vm_area_struct *dst_vma, + unsigned long dst_addr, struct page *page, + bool newly_allocated, bool wp_copy); + extern ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start, unsigned long src_start, unsigned long len, bool *mmap_changing, __u64 mode); diff --git a/mm/shmem.c b/mm/shmem.c index e361f1d81c8d..2e9f56c83489 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2378,14 +2378,11 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, struct address_space *mapping = inode->i_mapping; gfp_t gfp = mapping_gfp_mask(mapping); pgoff_t pgoff = linear_page_index(dst_vma, dst_addr); - spinlock_t *ptl; void *page_kaddr; struct page *page; - pte_t _dst_pte, *dst_pte; int ret; pgoff_t max_off; - ret = -ENOMEM; if (!shmem_inode_acct_block(inode, 1)) { /* * We may have got a page, returned -ENOENT triggering a retry, @@ -2396,10 +2393,11 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, put_page(*pagep); *pagep = NULL; } - goto out; + return -ENOMEM; } if (!*pagep) { + ret = -ENOMEM; page = shmem_alloc_page(gfp, info, pgoff); if (!page) goto out_unacct_blocks; @@ -2414,9 +2412,9 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, /* fallback to copy_from_user outside mmap_lock */ if (unlikely(ret)) { *pagep = page; - shmem_inode_unacct_blocks(inode, 1); + ret = -ENOENT; /* don't free the page */ - return -ENOENT; + goto out_unacct_blocks; } } else { /* ZEROPAGE */ clear_highpage(page); @@ -2442,32 +2440,10 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, if (ret) goto out_release; - _dst_pte = mk_pte(page, dst_vma->vm_page_prot); - if (dst_vma->vm_flags & VM_WRITE) - _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte)); - else { - /* - * We don't set the pte dirty if the vma has no - * VM_WRITE permission, so mark the page dirty or it - * could be freed from under us. We could do it - * unconditionally before unlock_page(), but doing it - * only if VM_WRITE is not set is faster. - */ - set_page_dirty(page); - } - - dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl); - - ret = -EFAULT; - max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); - if (unlikely(pgoff >= max_off)) - goto out_release_unlock; - - ret = -EEXIST; - if (!pte_none(*dst_pte)) - goto out_release_unlock; - - lru_cache_add(page); + ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr, + page, true, false); + if (ret) + goto out_delete_from_cache; spin_lock_irq(&info->lock); info->alloced++; @@ -2475,27 +2451,17 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, shmem_recalc_inode(inode); spin_unlock_irq(&info->lock); - inc_mm_counter(dst_mm, mm_counter_file(page)); - page_add_file_rmap(page, false); - set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte); - - /* No need to invalidate - it was non-present before */ - update_mmu_cache(dst_vma, dst_addr, dst_pte); - pte_unmap_unlock(dst_pte, ptl); + SetPageDirty(page); unlock_page(page); - ret = 0; -out: - return ret; -out_release_unlock: - pte_unmap_unlock(dst_pte, ptl); - ClearPageDirty(page); + return 0; +out_delete_from_cache: delete_from_page_cache(page); out_release: unlock_page(page); put_page(page); out_unacct_blocks: shmem_inode_unacct_blocks(inode, 1); - goto out; + return ret; } #endif /* CONFIG_USERFAULTFD */ diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index d1ac73a0d2a9..5508f7d9e2dc 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -51,18 +51,13 @@ struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm, /* * Install PTEs, to map dst_addr (within dst_vma) to page. * - * This function handles MCOPY_ATOMIC_CONTINUE (which is always file-backed), - * whether or not dst_vma is VM_SHARED. It also handles the more general - * MCOPY_ATOMIC_NORMAL case, when dst_vma is *not* VM_SHARED (it may be file - * backed, or not). - * - * Note that MCOPY_ATOMIC_NORMAL for a VM_SHARED dst_vma is handled by - * shmem_mcopy_atomic_pte instead. + * This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem + * and anon, and for both shared and private VMAs. */ -static int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, - struct vm_area_struct *dst_vma, - unsigned long dst_addr, struct page *page, - bool newly_allocated, bool wp_copy) +int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd, + struct vm_area_struct *dst_vma, + unsigned long dst_addr, struct page *page, + bool newly_allocated, bool wp_copy) { int ret; pte_t _dst_pte, *dst_pte;
In a previous commit, we added the mfill_atomic_install_pte() helper. This helper does the job of setting up PTEs for an existing page, to map it into a given VMA. It deals with both the anon and shmem cases, as well as the shared and private cases. In other words, shmem_mfill_atomic_pte() duplicates a case it already handles. So, expose it, and let shmem_mfill_atomic_pte() use it directly, to reduce code duplication. This requires that we refactor shmem_mfill_atomic_pte() a bit: Instead of doing accounting (shmem_recalc_inode() et al) part-way through the PTE setup, do it afterward. This frees up mfill_atomic_install_pte() from having to care about this accounting, and means we don't need to e.g. shmem_uncharge() in the error path. A side effect is this switches shmem_mfill_atomic_pte() to use lru_cache_add_inactive_or_unevictable() instead of just lru_cache_add(). This wrapper does some extra accounting in an exceptional case, if appropriate, so it's actually the more correct thing to use. Signed-off-by: Axel Rasmussen <axelrasmussen@google.com> --- include/linux/userfaultfd_k.h | 5 +++ mm/shmem.c | 58 ++++++++--------------------------- mm/userfaultfd.c | 17 ++++------ 3 files changed, 23 insertions(+), 57 deletions(-)