From ec906cf7bee60f3bbc8500bac14e65813e38ac93 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Mon, 28 Sep 2026 11:54:30 -0400 Subject: [PATCH] pNFS/flexfiles: don't reset to MDS for v4 error when previous layout forbid it ff_layout_async_handle_error_v4() ends in -NFS4ERR_RESET_TO_MDS, which makes ff_layout_read_release() / ff_layout_write_release() call ff_layout_reset_read() or ff_layout_reset_write(hdr, false), and those call pnfs_read_done_resend_to_mds() / pnfs_write_done_resend_to_mds(). Those build a page I/O descriptor with force_mds set, so the flexfiles ->pg_init() never runs and no layout is consulted anywhere on the way: the READ or WRITE goes to the metadata server unconditionally. For a layout carrying FF_FLAGS_NO_IO_THRU_MDS that is exactly what the server forbade. The fall-through into reset: is already safe, because ff_layout_avoid_mds_available_ds() returns true for a segment with the flag and so answers -NFS4ERR_RESET_TO_PNFS first. What is not safe is the goto: the invalid-layout errors (NFS4ERR_PNFS_NO_LAYOUT, STALE, BADHANDLE, ISDIR, FHEXPIRED, WRONG_TYPE) call pnfs_destroy_layout() and jump straight to reset:, over that check. That is the case where the file had a perfectly good layout, something forced it to be given back, and the client answers by writing to the MDS behind the server's back. Test at reset: itself, so it covers the goto and any future one, and ask the inode (NFS_INO_NO_IO_THRU_MDS): the callers that jump here have just destroyed the layout hdr, so the hdr-level flag is no longer reachable, while the inode-level one is set for the life of the in-core inode. -NFS4ERR_RESET_TO_PNFS is the right answer rather than an error. It is what the fall-through already returns for the same flag, and the resends it drives - ff_layout_resend_pnfs_read() and ff_layout_reset_write(hdr, true) - re-enter the pgio path with force_mds clear, so a fresh LAYOUTGET is taken, which is precisely what a destroyed layout needs. A LAYOUTGET that fails fatally makes pnfs_update_layout() return an error, which ->pg_init() reports; a non-fatal refusal (NFS4ERR_LAYOUTUNAVAILABLE, NFS4ERR_TOOSMALL) returns no segment instead, and the client keeps retrying through pNFS rather than falling back. ff_layout_async_handle_error_v3() needs no such change: it returns only -NFS4ERR_RESET_TO_PNFS or -EAGAIN. Fixes: 260074cd8413 ("pNFS/flexfiles: Add support for FF_FLAGS_NO_IO_THRU_MDS") Assisted-by: Claude:claude-opus-5[1m] Signed-off-by: Mike Snitzer Signed-off-by: Anna Schumaker --- fs/nfs/flexfilelayout/flexfilelayout.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c index 84d22f715653..d4f2b57e9d5b 100644 --- a/fs/nfs/flexfilelayout/flexfilelayout.c +++ b/fs/nfs/flexfilelayout/flexfilelayout.c @@ -1423,6 +1423,23 @@ static int ff_layout_async_handle_error_v4(struct rpc_task *task, if (ff_layout_avoid_mds_available_ds(lseg)) return -NFS4ERR_RESET_TO_PNFS; reset: + /* + * FF_FLAGS_NO_IO_THRU_MDS: never resend through the MDS. The + * caller would do so with force_mds set (ff_layout_reset_read(), + * ff_layout_reset_write(hdr, false) -> pnfs_*_done_resend_to_mds()), + * which builds a descriptor out of the plain MDS page ops and so + * consults no layout at all -- this is the last point at which the + * policy can still be applied. Retry through pNFS instead, which + * takes a fresh LAYOUTGET; that is also the right answer for the + * invalid-layout cases that jump here, since they have just called + * pnfs_destroy_layout(). Having done so they can no longer ask the + * layout hdr about the flag, hence the inode. + */ + if (nfs_no_io_thru_mds(inode)) { + dprintk("%s Retry through pNFS, no MDS fallback. Error %d\n", + __func__, task->tk_status); + return -NFS4ERR_RESET_TO_PNFS; + } dprintk("%s Retry through MDS. Error %d\n", __func__, task->tk_status); return -NFS4ERR_RESET_TO_MDS;