github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-11-07 06:17:02 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

pNFS/flexfiles: don't read through MDS when previous layout forbid it

Browse Source 
ff_layout_pg_init_read() falls back to the MDS whenever
pnfs_update_layout() returns no segment and no error: a bulk
CB_LAYOUTRECALL (FSID, DEVICEID or ALL), LAYOUTGETs blocked behind a
layout being returned, or a LAYOUTGET refused with
NFS4ERR_LAYOUTUNAVAILABLE or NFS4ERR_TOOSMALL, which set the per-iomode
fail bit for PNFS_LAYOUTGET_RETRY_TIMEOUT.  That is the read-side twin
of the write path fixed by commit 1d62e659c0 ("NFSv4/flexfiles:
honor FF_FLAGS_NO_IO_THRU_MDS in pg_get_mirror_count_write"), and it
is reached in exactly the situation that matters most: the file had a
valid layout, the layout had to go back, and the next one has not
arrived yet.

The write side could answer -EAGAIN because writeback owns the retry and
redirties the page.  A read has no such owner, so -EAGAIN here would
surface as an I/O error to the application.  Wait for a layout instead,
on the same terms the function already uses when the layout lookup
itself returns -EAGAIN: sleep a second and retry, bounded by
pg_maxretrans, which ff_layout_pg_init_read() sets only for soft and
softerr mounts.  A hard mount therefore waits, which is what a hard
mount is for, and matches what the FF_FLAGS_NO_IO_THRU_MDS check on the
data server selection a few lines above already does.  That includes
waiting out NFS4ERR_LAYOUTUNAVAILABLE: a file that was given a layout
with this flag must not be read off the MDS, whatever the server says
afterwards.

The test asks the inode (NFS_INO_NO_IO_THRU_MDS) rather than the layout
hdr, because in this path there is no segment, and the hdr that carried
the flag may already have been destroyed.  Where a segment is in hand -
the data server selection above, ff_layout_read_pagelist() - the
existing per-segment ff_layout_no_fallback_to_mds() test stays, since it
is the more precise question.

Fixes: 260074cd84 ("pNFS/flexfiles: Add support for FF_FLAGS_NO_IO_THRU_MDS")
Assisted-by: Claude:claude-opus-5[1m]
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@hammerspace.com>
This commit is contained in:
Mike Snitzer 2026-09-28 11:54:29 -04:00 committed by Anna Schumaker
parent 78422f623c
commit 2f007ba074
1 changed files with 26 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
fs/nfs/flexfilelayout/flexfilelayout.c
View File

@ -1073,19 +1073,33 @@ ff_layout_pg_init_read(struct nfs_pageio_descriptor *pgio,
if (pgio->pg_error < 0) {
if (pgio->pg_error != -EAGAIN)
return;
/* Retry getting layout segment if lower layer returned -EAGAIN */
if (pgio->pg_maxretrans && req->wb_nio++ > pgio->pg_maxretrans) {
if (NFS_SERVER(pgio->pg_inode)->flags & NFS_MOUNT_SOFTERR)
pgio->pg_error = -ETIMEDOUT;
else
pgio->pg_error = -EIO;
return;
}
pgio->pg_error = 0;
/* Sleep for 1 second before retrying */
ssleep(1);
goto retry;
goto retry_nolseg;
}
/*
* No segment, and no error to report either: pnfs_update_layout()
* simply has nothing to give (NFS_LAYOUT_BULK_RECALL, a failed
* pnfs_layout_io_test, blocked LAYOUTGETs, a layout being
* returned). If the server forbids reading this file through the
* MDS there is no fallback to take, so wait for a layout on the
* same terms as the -EAGAIN above. The layout hdr that carried
* FF_FLAGS_NO_IO_THRU_MDS may itself be gone by now, which is why
* this asks the inode and not the hdr.
*/
if (!nfs_no_io_thru_mds(pgio->pg_inode))
goto out_mds;
retry_nolseg:
/* Retry getting layout segment if lower layer returned -EAGAIN */
if (pgio->pg_maxretrans && req->wb_nio++ > pgio->pg_maxretrans) {
if (NFS_SERVER(pgio->pg_inode)->flags & NFS_MOUNT_SOFTERR)
pgio->pg_error = -ETIMEDOUT;
else
pgio->pg_error = -EIO;
return;
}
pgio->pg_error = 0;
/* Sleep for 1 second before retrying */
ssleep(1);
goto retry;
out_mds:
trace_pnfs_mds_fallback_pg_init_read(pgio->pg_inode,
0, NFS4_MAX_UINT64, IOMODE_READ,