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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 /* * oh the beauties of C type declarations. diff --git a/mm/filemap.c b/mm/filemap.c index fe37bd2b2630..4dadd1a4ca7c 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3287,10 +3287,12 @@ struct page *grab_cache_page_write_begin(struct address_space *mapping, pgoff_t index, unsigned flags) { struct page *page; - int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT; + int fgp_flags = FGP_LOCK|FGP_WRITE; if (flags & AOP_FLAG_NOFS) fgp_flags |= FGP_NOFS; + if (!(flags & AOP_FLAG_UNCACHED)) + fgp_flags |= FGP_CREAT; page = pagecache_get_page(mapping, index, fgp_flags, mapping_gfp_mask(mapping)); @@ -3311,6 +3313,9 @@ ssize_t generic_perform_write(struct file *file, ssize_t written = 0; unsigned int flags = 0; + if (iocb->ki_flags & IOCB_UNCACHED) + flags |= AOP_FLAG_UNCACHED; + do { struct page *page; unsigned long offset; /* Offset into pagecache page */ @@ -3343,10 +3348,16 @@ ssize_t generic_perform_write(struct file *file, break; } +retry: status = a_ops->write_begin(file, mapping, pos, bytes, flags, &page, &fsdata); - if (unlikely(status < 0)) + if (unlikely(status < 0)) { + if (status == -ENOMEM && (flags & AOP_FLAG_UNCACHED)) { + flags &= ~AOP_FLAG_UNCACHED; + goto retry; + } break; + } if (mapping_writably_mapped(mapping)) flush_dcache_page(page); @@ -3382,6 +3393,32 @@ ssize_t generic_perform_write(struct file *file, balance_dirty_pages_ratelimited(mapping); } while (iov_iter_count(i)); + if (written && (iocb->ki_flags & IOCB_UNCACHED)) { + loff_t end; + + pos = iocb->ki_pos; + end = pos + written; + + status = 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);