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If new pages aren't instantiated, we leave them alone. This provides similar semantics to reads with RWF_UNCACHED set. Signed-off-by: Jens Axboe --- include/linux/fs.h | 1 + mm/filemap.c | 41 +++++++++++++++++++++++++++++++++++++++-- 2 files changed, 40 insertions(+), 2 deletions(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index bf58db1bc032..5ea5fc167524 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -285,6 +285,7 @@ enum positive_aop_returns { #define AOP_FLAG_NOFS 0x0002 /* used by filesystem to direct * helper code (eg buffer layer) * to clear GFP_FS from alloc */ +#define AOP_FLAG_UNCACHED 0x0004 =20 /* * oh the beauties of C type declarations. diff --git a/mm/filemap.c b/mm/filemap.c index 00b8e87fb9cf..fbcd4537979d 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3277,10 +3277,12 @@ struct page *grab_cache_page_write_begin(struct a= ddress_space *mapping, pgoff_t index, unsigned flags) { struct page *page; - int fgp_flags =3D FGP_LOCK|FGP_WRITE|FGP_CREAT; + int fgp_flags =3D FGP_LOCK|FGP_WRITE; =20 if (flags & AOP_FLAG_NOFS) fgp_flags |=3D FGP_NOFS; + if (!(flags & AOP_FLAG_UNCACHED)) + fgp_flags |=3D FGP_CREAT; =20 page =3D pagecache_get_page(mapping, index, fgp_flags, mapping_gfp_mask(mapping)); @@ -3301,6 +3303,9 @@ ssize_t generic_perform_write(struct file *file, ssize_t written =3D 0; unsigned int flags =3D 0; =20 + if (iocb->ki_flags & IOCB_UNCACHED) + flags |=3D AOP_FLAG_UNCACHED; + do { struct page *page; unsigned long offset; /* Offset into pagecache page */ @@ -3333,10 +3338,16 @@ ssize_t generic_perform_write(struct file *file, break; } =20 +retry: status =3D a_ops->write_begin(file, mapping, pos, bytes, flags, &page, &fsdata); - if (unlikely(status < 0)) + if (unlikely(status < 0)) { + if (status =3D=3D -ENOMEM && (flags & AOP_FLAG_UNCACHED)) { + flags &=3D ~AOP_FLAG_UNCACHED; + goto retry; + } break; + } =20 if (mapping_writably_mapped(mapping)) flush_dcache_page(page); @@ -3372,6 +3383,32 @@ ssize_t generic_perform_write(struct file *file, balance_dirty_pages_ratelimited(mapping); } while (iov_iter_count(i)); =20 + if (written && (iocb->ki_flags & IOCB_UNCACHED)) { + loff_t end; + + pos =3D iocb->ki_pos; + end =3D pos + written; + + status =3D filemap_write_and_wait_range(mapping, pos, end); + if (status) + goto out; + + /* + * No pages were created for this range, we're done + */ + if (flags & AOP_FLAG_UNCACHED) + goto out; + + /* + * Try to invalidate cache pages for the range we just wrote. + * We don't care if invalidation fails as the write has still + * worked and leaving clean uptodate pages in the page cache + * isn't a corruption vector for uncached IO. + */ + invalidate_inode_pages2_range(mapping, + pos >> PAGE_SHIFT, end >> PAGE_SHIFT); + } +out: return written ? written : status; } EXPORT_SYMBOL(generic_perform_write); --=20 2.24.1