Re: [PATCH v3] pNFS/flexfiles: don't attempt pnfs on fatal DS errors

["Mkrtchyan, Tigran" <tigran.mkrtchyan@desy.de>]

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Dear fellows,

Any comments on this?

Thanks,
  Tigran.

----- Original Message -----
> From: "Tigran Mkrtchyan" <tigran.mkrtchyan@desy.de>
> To: "linux-nfs" <linux-nfs@vger.kernel.org>
> Cc: "Trond Myklebust" <trondmy@kernel.org>, "Anna Schumaker" <anna@kernel.org>, "Tigran Mkrtchyan"
> <tigran.mkrtchyan@desy.de>
> Sent: Friday, 27 June, 2025 09:17:51
> Subject: [PATCH v3] pNFS/flexfiles: don't attempt pnfs on fatal DS errors

> Fixes: 260f32adb88 ("pNFS/flexfiles: Check the result of nfs4_pnfs_ds_connect")
> 
> When an applications get killed (SIGTERM/SIGINT) while pNFS client performs a
> connection
> to DS, client ends in an infinite loop of connect-disconnect. This
> source of the issue, it that flexfilelayoutdev#nfs4_ff_layout_prepare_ds gets an
> error
> on nfs4_pnfs_ds_connect with status ERESTARTSYS, which is set by
> rpc_signal_task, but
> the error is treated as transient, thus retried.
> 
> The issue is reproducible with Ctrl+C the following script(there should be ~1000
> files in
> a directory, client should must not have any connections to DSes):
> 
> ```
> echo 3 > /proc/sys/vm/drop_caches
> 
> for i in *
> do
>   head -1 $i
> done
> ```
> 
> The change aims to propagate the nfs4_ff_layout_prepare_ds error state
> to the caller that can decide whatever this is a retryable error or not.
> 
> Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
> ---
> fs/nfs/flexfilelayout/flexfilelayout.c    | 26 ++++++++++++++---------
> fs/nfs/flexfilelayout/flexfilelayoutdev.c |  6 +++---
> 2 files changed, 19 insertions(+), 13 deletions(-)
> 
> diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c
> b/fs/nfs/flexfilelayout/flexfilelayout.c
> index 708cbfbccea5..a67001b4dbdf 100644
> --- a/fs/nfs/flexfilelayout/flexfilelayout.c
> +++ b/fs/nfs/flexfilelayout/flexfilelayout.c
> @@ -762,14 +762,14 @@ ff_layout_choose_ds_for_read(struct pnfs_layout_segment
> *lseg,
> {
> 	struct nfs4_ff_layout_segment *fls = FF_LAYOUT_LSEG(lseg);
> 	struct nfs4_ff_layout_mirror *mirror;
> -	struct nfs4_pnfs_ds *ds;
> +	struct nfs4_pnfs_ds *ds = ERR_PTR(-EAGAIN);
> 	u32 idx;
> 
> 	/* mirrors are initially sorted by efficiency */
> 	for (idx = start_idx; idx < fls->mirror_array_cnt; idx++) {
> 		mirror = FF_LAYOUT_COMP(lseg, idx);
> 		ds = nfs4_ff_layout_prepare_ds(lseg, mirror, false);
> -		if (!ds)
> +		if (IS_ERR(ds))
> 			continue;
> 
> 		if (check_device &&
> @@ -777,10 +777,10 @@ ff_layout_choose_ds_for_read(struct pnfs_layout_segment
> *lseg,
> 			continue;
> 
> 		*best_idx = idx;
> -		return ds;
> +		break;
> 	}
> 
> -	return NULL;
> +	return ds;
> }
> 
> static struct nfs4_pnfs_ds *
> @@ -942,7 +942,7 @@ ff_layout_pg_init_write(struct nfs_pageio_descriptor *pgio,
> 	for (i = 0; i < pgio->pg_mirror_count; i++) {
> 		mirror = FF_LAYOUT_COMP(pgio->pg_lseg, i);
> 		ds = nfs4_ff_layout_prepare_ds(pgio->pg_lseg, mirror, true);
> -		if (!ds) {
> +		if (IS_ERR(ds)) {
> 			if (!ff_layout_no_fallback_to_mds(pgio->pg_lseg))
> 				goto out_mds;
> 			pnfs_generic_pg_cleanup(pgio);
> @@ -1808,6 +1808,7 @@ ff_layout_read_pagelist(struct nfs_pgio_header *hdr)
> 	u32 idx = hdr->pgio_mirror_idx;
> 	int vers;
> 	struct nfs_fh *fh;
> +	bool ds_fatal_error = false;
> 
> 	dprintk("--> %s ino %lu pgbase %u req %zu@%llu\n",
> 		__func__, hdr->inode->i_ino,
> @@ -1815,8 +1816,10 @@ ff_layout_read_pagelist(struct nfs_pgio_header *hdr)
> 
> 	mirror = FF_LAYOUT_COMP(lseg, idx);
> 	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, false);
> -	if (!ds)
> +	if (IS_ERR(ds)) {
> +		ds_fatal_error = nfs_error_is_fatal(PTR_ERR(ds));
> 		goto out_failed;
> +	}
> 
> 	ds_clnt = nfs4_ff_find_or_create_ds_client(mirror, ds->ds_clp,
> 						   hdr->inode);
> @@ -1864,7 +1867,7 @@ ff_layout_read_pagelist(struct nfs_pgio_header *hdr)
> 	return PNFS_ATTEMPTED;
> 
> out_failed:
> -	if (ff_layout_avoid_mds_available_ds(lseg))
> +	if (ff_layout_avoid_mds_available_ds(lseg) && !ds_fatal_error)
> 		return PNFS_TRY_AGAIN;
> 	trace_pnfs_mds_fallback_read_pagelist(hdr->inode,
> 			hdr->args.offset, hdr->args.count,
> @@ -1886,11 +1889,14 @@ ff_layout_write_pagelist(struct nfs_pgio_header *hdr,
> int sync)
> 	int vers;
> 	struct nfs_fh *fh;
> 	u32 idx = hdr->pgio_mirror_idx;
> +	bool ds_fatal_error = false;
> 
> 	mirror = FF_LAYOUT_COMP(lseg, idx);
> 	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, true);
> -	if (!ds)
> +	if (IS_ERR(ds)) {
> +		ds_fatal_error = nfs_error_is_fatal(PTR_ERR(ds));
> 		goto out_failed;
> +	}
> 
> 	ds_clnt = nfs4_ff_find_or_create_ds_client(mirror, ds->ds_clp,
> 						   hdr->inode);
> @@ -1941,7 +1947,7 @@ ff_layout_write_pagelist(struct nfs_pgio_header *hdr, int
> sync)
> 	return PNFS_ATTEMPTED;
> 
> out_failed:
> -	if (ff_layout_avoid_mds_available_ds(lseg))
> +	if (ff_layout_avoid_mds_available_ds(lseg) && !ds_fatal_error)
> 		return PNFS_TRY_AGAIN;
> 	trace_pnfs_mds_fallback_write_pagelist(hdr->inode,
> 			hdr->args.offset, hdr->args.count,
> @@ -1984,7 +1990,7 @@ static int ff_layout_initiate_commit(struct
> nfs_commit_data *data, int how)
> 	idx = calc_ds_index_from_commit(lseg, data->ds_commit_index);
> 	mirror = FF_LAYOUT_COMP(lseg, idx);
> 	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, true);
> -	if (!ds)
> +	if (IS_ERR(ds))
> 		goto out_err;
> 
> 	ds_clnt = nfs4_ff_find_or_create_ds_client(mirror, ds->ds_clp,
> diff --git a/fs/nfs/flexfilelayout/flexfilelayoutdev.c
> b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
> index 4a304cf17c4b..ef535baeefb6 100644
> --- a/fs/nfs/flexfilelayout/flexfilelayoutdev.c
> +++ b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
> @@ -370,11 +370,11 @@ nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment
> *lseg,
> 			  struct nfs4_ff_layout_mirror *mirror,
> 			  bool fail_return)
> {
> -	struct nfs4_pnfs_ds *ds = NULL;
> +	struct nfs4_pnfs_ds *ds;
> 	struct inode *ino = lseg->pls_layout->plh_inode;
> 	struct nfs_server *s = NFS_SERVER(ino);
> 	unsigned int max_payload;
> -	int status;
> +	int status = -EAGAIN;
> 
> 	if (!ff_layout_init_mirror_ds(lseg->pls_layout, mirror))
> 		goto noconnect;
> @@ -418,7 +418,7 @@ nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg,
> 	ff_layout_send_layouterror(lseg);
> 	if (fail_return || !ff_layout_has_available_ds(lseg))
> 		pnfs_error_mark_layout_for_return(ino, lseg);
> -	ds = NULL;
> +	ds = ERR_PTR(status);
> out:
> 	return ds;
> }
> --
> 2.50.0

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