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NFSv4/flexfiles: honor FF_FLAGS_NO_IO_THRU_MDS on fatal DS connect errors

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Commit f06bedfa62 ("pNFS/flexfiles: don't attempt pnfs on fatal DS
errors") teaches ff_layout_{read,write}_pagelist() to return
PNFS_NOT_ATTEMPTED when nfs4_ff_layout_prepare_ds() fails with a
nfs_error_is_fatal() errno (e.g. -ETIMEDOUT from a SOFTCONN connect
deadline, -ENOMEM, -ERESTARTSYS), so that the client gives up instead
of spinning.  pnfs_do_{read,write}() then dispatches the I/O through
pnfs_{read,write}_through_mds() → nfs_pageio_reset_{read,write}_mds().

That fallback is unconditional and silently violates FF_FLAGS_NO_IO_THRU_MDS:
when the layout segment carries the flag (typically single-mirror
appliance layouts where MDS I/O is explicitly forbidden), the
out_failed: path's \`&& !ds_fatal_error\` clause overrides the flag's
short-circuit through ff_layout_avoid_mds_available_ds() and routes
the I/O to the MDS file handle anyway.

This is reachable in practice during a data-server restart: SOFTCONN
exhaustion produces -ETIMEDOUT, which is fatal per nfs_error_is_fatal(),
which triggers PNFS_NOT_ATTEMPTED, which silently goes to MDS.

Preserve the upstream "don't spin on fatal errors" intent for layouts
that permit MDS fallback.  For layouts with FF_FLAGS_NO_IO_THRU_MDS
set, mark the layout for return and request PNFS_TRY_AGAIN instead;
if the server cannot supply a usable layout the failure now surfaces
cleanly via pnfs_update_layout(), rather than via silent MDS I/O that
contradicts the flag.

Fixes: f06bedfa62 ("pNFS/flexfiles: don't attempt pnfs on fatal DS errors")
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@hammerspace.com>
This commit is contained in:
Mike Snitzer 2026-06-04 16:24:02 -04:00 committed by Anna Schumaker
parent 17d90b68c3
commit 7a375cafc1
1 changed files with 16 additions and 0 deletions
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16
fs/nfs/flexfilelayout/flexfilelayout.c
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@ -2204,6 +2204,14 @@ ff_layout_read_pagelist(struct nfs_pgio_header *hdr)
out_failed:
if (ff_layout_avoid_mds_available_ds(lseg) && !ds_fatal_error)
return PNFS_TRY_AGAIN;
if (ff_layout_no_fallback_to_mds(lseg)) {
/*
* FF_FLAGS_NO_IO_THRU_MDS: force fresh LAYOUTGET,
* never fall through to MDS I/O.
*/
pnfs_error_mark_layout_for_return(hdr->inode, lseg);
return PNFS_TRY_AGAIN;
}
trace_pnfs_mds_fallback_read_pagelist(hdr->inode,
hdr->args.offset, hdr->args.count,
IOMODE_READ, NFS_I(hdr->inode)->layout, lseg);
@ -2289,6 +2297,14 @@ ff_layout_write_pagelist(struct nfs_pgio_header *hdr, int sync)
out_failed:
if (ff_layout_avoid_mds_available_ds(lseg) && !ds_fatal_error)
return PNFS_TRY_AGAIN;
if (ff_layout_no_fallback_to_mds(lseg)) {
/*
* FF_FLAGS_NO_IO_THRU_MDS: force fresh LAYOUTGET,
* never fall through to MDS I/O.
*/
pnfs_error_mark_layout_for_return(hdr->inode, lseg);
return PNFS_TRY_AGAIN;
}
trace_pnfs_mds_fallback_write_pagelist(hdr->inode,
hdr->args.offset, hdr->args.count,
IOMODE_RW, NFS_I(hdr->inode)->layout, lseg);