Re: [PATCH 04/10] fs: Introduce RWF_NOWAIT
From: Jan Kara <hidden>
Date: 2017-05-15 12:08:36
Also in:
linux-block, linux-btrfs, linux-ext4, linux-fsdevel, linux-xfs
On Thu 11-05-17 14:17:04, Goldwyn Rodrigues wrote:
From: Goldwyn Rodrigues <rgoldwyn-IBi9RG/b67k@public.gmane.org> RWF_NOWAIT informs kernel to bail out if an AIO request will block for reasons such as file allocations, or a writeback triggered, or would block while allocating requests while performing direct I/O. RWF_NOWAIT is translated to IOCB_NOWAIT for iocb->ki_flags. The check for -EOPNOTSUPP is placed in generic_file_write_iter(). This is called by most filesystems, either through fsops.write_iter() or through the function defined by write_iter(). If not, we perform the check defined by .write_iter() which is called for direct IO specifically. Filesystems xfs, btrfs and ext4 would be supported in the following patches.
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quoted hunk ↗ jump to hunk
diff --git a/fs/aio.c b/fs/aio.c index 020fa0045e3c..34027b67e2f4 100644 --- a/fs/aio.c +++ b/fs/aio.c@@ -1592,6 +1592,12 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, goto out_put_req; } + if ((req->common.ki_flags & IOCB_NOWAIT) && + !(req->common.ki_flags & IOCB_DIRECT)) { + ret = -EOPNOTSUPP; + goto out_put_req; + } + ret = put_user(KIOCB_KEY, &user_iocb->aio_key); if (unlikely(ret)) { pr_debug("EFAULT: aio_key\n");
I think you need to also check here that the IO is write. So that NOWAIT reads don't silently pass. Honza -- Jan Kara [off-list ref] SUSE Labs, CR