diff options
| -rw-r--r-- | arch/s390/kernel/uv.c | 66 |
1 files changed, 60 insertions, 6 deletions
diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c index f6ddb2b54032e6..d278bf0c09d1b3 100644 --- a/arch/s390/kernel/uv.c +++ b/arch/s390/kernel/uv.c @@ -15,6 +15,7 @@ #include <linux/pagemap.h> #include <linux/swap.h> #include <linux/pagewalk.h> +#include <linux/backing-dev.h> #include <asm/facility.h> #include <asm/sections.h> #include <asm/uv.h> @@ -338,22 +339,75 @@ static int make_folio_secure(struct mm_struct *mm, struct folio *folio, struct u */ static int s390_wiggle_split_folio(struct mm_struct *mm, struct folio *folio) { - int rc; + int rc, tried_splits; lockdep_assert_not_held(&mm->mmap_lock); folio_wait_writeback(folio); lru_add_drain_all(); - if (folio_test_large(folio)) { + if (!folio_test_large(folio)) + return 0; + + for (tried_splits = 0; tried_splits < 2; tried_splits++) { + struct address_space *mapping; + loff_t lstart, lend; + struct inode *inode; + folio_lock(folio); rc = split_folio(folio); + if (rc != -EBUSY) { + folio_unlock(folio); + return rc; + } + + /* + * Splitting with -EBUSY can fail for various reasons, but we + * have to handle one case explicitly for now: some mappings + * don't allow for splitting dirty folios; writeback will + * mark them clean again, including marking all page table + * entries mapping the folio read-only, to catch future write + * attempts. + * + * While the system should be writing back dirty folios in the + * background, we obtained this folio by looking up a writable + * page table entry. On these problematic mappings, writable + * page table entries imply dirty folios, preventing the + * split in the first place. + * + * To prevent a livelock when trigger writeback manually and + * letting the caller look up the folio again in the page + * table (turning it dirty), immediately try to split again. + * + * This is only a problem for some mappings (e.g., XFS); + * mappings that do not support writeback (e.g., shmem) do not + * apply. + */ + if (!folio_test_dirty(folio) || folio_test_anon(folio) || + !folio->mapping || !mapping_can_writeback(folio->mapping)) { + folio_unlock(folio); + break; + } + + /* + * Ideally, we'd only trigger writeback on this exact folio. But + * there is no easy way to do that, so we'll stabilize the + * mapping while we still hold the folio lock, so we can drop + * the folio lock to trigger writeback on the range currently + * covered by the folio instead. + */ + mapping = folio->mapping; + lstart = folio_pos(folio); + lend = lstart + folio_size(folio) - 1; + inode = igrab(mapping->host); folio_unlock(folio); - if (rc != -EBUSY) - return rc; - return -EAGAIN; + if (unlikely(!inode)) + break; + + filemap_write_and_wait_range(mapping, lstart, lend); + iput(mapping->host); } - return 0; + return -EAGAIN; } int make_hva_secure(struct mm_struct *mm, unsigned long hva, struct uv_cb_header *uvcb) |