diff options
| -rw-r--r-- | mm/shmem.c | 50 |
1 files changed, 26 insertions, 24 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index 54bec60380df..ceba031d9985 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2620,12 +2620,13 @@ static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence) /* * We need a tag: a new tag would expand every radix_tree_node by 8 bytes, - * so reuse a tag which we firmly believe is never set or cleared on shmem. + * so reuse a tag which we firmly believe is never set or cleared on tmpfs + * or hugetlbfs because they are memory only filesystems. */ -#define SHMEM_TAG_PINNED PAGECACHE_TAG_TOWRITE +#define MEMFD_TAG_PINNED PAGECACHE_TAG_TOWRITE #define LAST_SCAN 4 /* about 150ms max */ -static void shmem_tag_pins(struct address_space *mapping) +static void memfd_tag_pins(struct address_space *mapping) { struct radix_tree_iter iter; void __rcu **slot; @@ -2646,7 +2647,7 @@ static void shmem_tag_pins(struct address_space *mapping) } else if (page_count(page) - page_mapcount(page) > 1) { xa_lock_irq(&mapping->i_pages); radix_tree_tag_set(&mapping->i_pages, iter.index, - SHMEM_TAG_PINNED); + MEMFD_TAG_PINNED); xa_unlock_irq(&mapping->i_pages); } @@ -2667,7 +2668,7 @@ static void shmem_tag_pins(struct address_space *mapping) * The caller must guarantee that no new user will acquire writable references * to those pages to avoid races. */ -static int shmem_wait_for_pins(struct address_space *mapping) +static int memfd_wait_for_pins(struct address_space *mapping) { struct radix_tree_iter iter; void __rcu **slot; @@ -2675,11 +2676,11 @@ static int shmem_wait_for_pins(struct address_space *mapping) struct page *page; int error, scan; - shmem_tag_pins(mapping); + memfd_tag_pins(mapping); error = 0; for (scan = 0; scan <= LAST_SCAN; scan++) { - if (!radix_tree_tagged(&mapping->i_pages, SHMEM_TAG_PINNED)) + if (!radix_tree_tagged(&mapping->i_pages, MEMFD_TAG_PINNED)) break; if (!scan) @@ -2690,7 +2691,7 @@ static int shmem_wait_for_pins(struct address_space *mapping) start = 0; rcu_read_lock(); radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, - start, SHMEM_TAG_PINNED) { + start, MEMFD_TAG_PINNED) { page = radix_tree_deref_slot(slot); if (radix_tree_exception(page)) { @@ -2717,7 +2718,7 @@ static int shmem_wait_for_pins(struct address_space *mapping) xa_lock_irq(&mapping->i_pages); radix_tree_tag_clear(&mapping->i_pages, - iter.index, SHMEM_TAG_PINNED); + iter.index, MEMFD_TAG_PINNED); xa_unlock_irq(&mapping->i_pages); continue_resched: if (need_resched()) { @@ -2733,11 +2734,11 @@ continue_resched: static unsigned int *memfd_file_seals_ptr(struct file *file) { - if (file->f_op == &shmem_file_operations) + if (shmem_file(file)) return &SHMEM_I(file_inode(file))->seals; #ifdef CONFIG_HUGETLBFS - if (file->f_op == &hugetlbfs_file_operations) + if (is_file_hugepages(file)) return &HUGETLBFS_I(file_inode(file))->seals; #endif @@ -2757,16 +2758,17 @@ static int memfd_add_seals(struct file *file, unsigned int seals) /* * SEALING - * Sealing allows multiple parties to share a shmem-file but restrict - * access to a specific subset of file operations. Seals can only be - * added, but never removed. This way, mutually untrusted parties can - * share common memory regions with a well-defined policy. A malicious - * peer can thus never perform unwanted operations on a shared object. + * Sealing allows multiple parties to share a tmpfs or hugetlbfs file + * but restrict access to a specific subset of file operations. Seals + * can only be added, but never removed. This way, mutually untrusted + * parties can share common memory regions with a well-defined policy. + * A malicious peer can thus never perform unwanted operations on a + * shared object. * - * Seals are only supported on special shmem-files and always affect - * the whole underlying inode. Once a seal is set, it may prevent some - * kinds of access to the file. Currently, the following seals are - * defined: + * Seals are only supported on special tmpfs or hugetlbfs files and + * always affect the whole underlying inode. Once a seal is set, it + * may prevent some kinds of access to the file. Currently, the + * following seals are defined: * SEAL_SEAL: Prevent further seals from being set on this file * SEAL_SHRINK: Prevent the file from shrinking * SEAL_GROW: Prevent the file from growing @@ -2780,9 +2782,9 @@ static int memfd_add_seals(struct file *file, unsigned int seals) * added. * * Semantics of sealing are only defined on volatile files. Only - * anonymous shmem files support sealing. More importantly, seals are - * never written to disk. Therefore, there's no plan to support it on - * other file types. + * anonymous tmpfs and hugetlbfs files support sealing. More + * importantly, seals are never written to disk. Therefore, there's + * no plan to support it on other file types. */ if (!(file->f_mode & FMODE_WRITE)) @@ -2808,7 +2810,7 @@ static int memfd_add_seals(struct file *file, unsigned int seals) if (error) goto unlock; - error = shmem_wait_for_pins(file->f_mapping); + error = memfd_wait_for_pins(file->f_mapping); if (error) { mapping_allow_writable(file->f_mapping); goto unlock; |