Commit 25ba2b84 authored by Mike Snitzer's avatar Mike Snitzer Committed by Anna Schumaker
Browse files

nfs/localio: avoid issuing misaligned IO using O_DIRECT 



Add nfsd_file_dio_alignment and use it to avoid issuing misaligned IO
using O_DIRECT. Any misaligned DIO falls back to using buffered IO.

Because misaligned DIO is now handled safely, remove the nfs modparam
'localio_O_DIRECT_semantics' that was added to require users opt-in to
the requirement that all O_DIRECT be properly DIO-aligned.

Also, introduce nfs_iov_iter_aligned_bvec() which is a variant of
iov_iter_aligned_bvec() that also verifies the offset associated with
an iov_iter is DIO-aligned.  NOTE: in a parallel effort,
iov_iter_aligned_bvec() is being removed along with
iov_iter_is_aligned().

Lastly, add pr_info_ratelimited if underlying filesystem returns
-EINVAL because it was made to try O_DIRECT for IO that is not
DIO-aligned (shouldn't happen, so its best to be louder if it does).

Fixes: 3feec685 ("nfs/localio: add direct IO enablement with sync and async IO support")
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarAnna Schumaker <anna.schumaker@oracle.com>
parent fd6d93c2

fs/nfs/localio.c

+55 −10
Original line number Diff line number Diff line
@@ -49,11 +49,6 @@ struct nfs_local_fsync_ctx { 
static bool localio_enabled __read_mostly = true;

module_param(localio_enabled, bool, 0644);



static bool localio_O_DIRECT_semantics __read_mostly = false;

module_param(localio_O_DIRECT_semantics, bool, 0644);

MODULE_PARM_DESC(localio_O_DIRECT_semantics,

		 "LOCALIO will use O_DIRECT semantics to filesystem.");



static inline bool nfs_client_is_local(const struct nfs_client *clp)

{

	return !!rcu_access_pointer(clp->cl_uuid.net);
@@ -322,12 +317,9 @@ nfs_local_iocb_alloc(struct nfs_pgio_header *hdr, 
		return NULL;

	}



	if (localio_O_DIRECT_semantics &&

	    test_bit(NFS_IOHDR_ODIRECT, &hdr->flags)) {

		iocb->kiocb.ki_filp = file;

		iocb->kiocb.ki_flags = IOCB_DIRECT;

	} else

	init_sync_kiocb(&iocb->kiocb, file);

	if (test_bit(NFS_IOHDR_ODIRECT, &hdr->flags))

		iocb->kiocb.ki_flags = IOCB_DIRECT;



	iocb->kiocb.ki_pos = hdr->args.offset;

	iocb->hdr = hdr;
@@ -337,6 +329,30 @@ nfs_local_iocb_alloc(struct nfs_pgio_header *hdr, 
	return iocb;

}



static bool nfs_iov_iter_aligned_bvec(const struct iov_iter *i,

		loff_t offset, unsigned int addr_mask, unsigned int len_mask)

{

	const struct bio_vec *bvec = i->bvec;

	size_t skip = i->iov_offset;

	size_t size = i->count;



	if ((offset | size) & len_mask)

		return false;

	do {

		size_t len = bvec->bv_len;



		if (len > size)

			len = size;

		if ((unsigned long)(bvec->bv_offset + skip) & addr_mask)

			return false;

		bvec++;

		size -= len;

		skip = 0;

	} while (size);



	return true;

}



static void

nfs_local_iter_init(struct iov_iter *i, struct nfs_local_kiocb *iocb, int dir)

{
@@ -346,6 +362,25 @@ nfs_local_iter_init(struct iov_iter *i, struct nfs_local_kiocb *iocb, int dir) 
		      hdr->args.count + hdr->args.pgbase);

	if (hdr->args.pgbase != 0)

		iov_iter_advance(i, hdr->args.pgbase);



	if (iocb->kiocb.ki_flags & IOCB_DIRECT) {

		u32 nf_dio_mem_align, nf_dio_offset_align, nf_dio_read_offset_align;

		/* Verify the IO is DIO-aligned as required */

		nfs_to->nfsd_file_dio_alignment(iocb->localio, &nf_dio_mem_align,

						&nf_dio_offset_align,

						&nf_dio_read_offset_align);

		if (dir == READ)

			nf_dio_offset_align = nf_dio_read_offset_align;



		if (nf_dio_mem_align && nf_dio_offset_align &&

		    nfs_iov_iter_aligned_bvec(i, hdr->args.offset,

					      nf_dio_mem_align - 1,

					      nf_dio_offset_align - 1))

			return; /* is DIO-aligned */



		/* Fallback to using buffered for this misaligned IO */

		iocb->kiocb.ki_flags &= ~IOCB_DIRECT;

	}

}



static void
@@ -406,6 +441,11 @@ nfs_local_read_done(struct nfs_local_kiocb *iocb, long status) 
	struct nfs_pgio_header *hdr = iocb->hdr;

	struct file *filp = iocb->kiocb.ki_filp;



	if ((iocb->kiocb.ki_flags & IOCB_DIRECT) && status == -EINVAL) {

		/* Underlying FS will return -EINVAL if misaligned DIO is attempted. */

		pr_info_ratelimited("nfs: Unexpected direct I/O read alignment failure\n");

	}



	nfs_local_pgio_done(hdr, status);



	/*
@@ -598,6 +638,11 @@ nfs_local_write_done(struct nfs_local_kiocb *iocb, long status) 


	dprintk("%s: wrote %ld bytes.\n", __func__, status > 0 ? status : 0);



	if ((iocb->kiocb.ki_flags & IOCB_DIRECT) && status == -EINVAL) {

		/* Underlying FS will return -EINVAL if misaligned DIO is attempted. */

		pr_info_ratelimited("nfs: Unexpected direct I/O write alignment failure\n");

	}



	/* Handle short writes as if they are ENOSPC */

	if (status > 0 && status < hdr->args.count) {

		hdr->mds_offset += status;

fs/nfsd/localio.c

+11 −0
Original line number Diff line number Diff line
@@ -117,6 +117,16 @@ nfsd_open_local_fh(struct net *net, struct auth_domain *dom, 
	return localio;

}



static void nfsd_file_dio_alignment(struct nfsd_file *nf,

				    u32 *nf_dio_mem_align,

				    u32 *nf_dio_offset_align,

				    u32 *nf_dio_read_offset_align)

{

	*nf_dio_mem_align = nf->nf_dio_mem_align;

	*nf_dio_offset_align = nf->nf_dio_offset_align;

	*nf_dio_read_offset_align = nf->nf_dio_read_offset_align;

}



static const struct nfsd_localio_operations nfsd_localio_ops = {

	.nfsd_net_try_get  = nfsd_net_try_get,

	.nfsd_net_put  = nfsd_net_put,
@@ -124,6 +134,7 @@ static const struct nfsd_localio_operations nfsd_localio_ops = { 
	.nfsd_file_put_local = nfsd_file_put_local,

	.nfsd_file_get_local = nfsd_file_get_local,

	.nfsd_file_file = nfsd_file_file,

	.nfsd_file_dio_alignment = nfsd_file_dio_alignment,

};



void nfsd_localio_ops_init(void)

include/linux/nfslocalio.h

+2 −0
Original line number Diff line number Diff line
@@ -65,6 +65,8 @@ struct nfsd_localio_operations { 
	struct net *(*nfsd_file_put_local)(struct nfsd_file __rcu **);

	struct nfsd_file *(*nfsd_file_get_local)(struct nfsd_file *);

	struct file *(*nfsd_file_file)(struct nfsd_file *);

	void (*nfsd_file_dio_alignment)(struct nfsd_file *,

					u32 *, u32 *, u32 *);

} ____cacheline_aligned;



extern void nfsd_localio_ops_init(void);