On 26/01/08 03:17PM, Jonathan Cameron wrote:
> On Wed, 7 Jan 2026 09:33:27 -0600
> John Groves <[email protected]> wrote:
>
> > Memory errors are at least somewhat more likely on disaggregated memory
> > than on-board memory. This commit registers to be notified by fsdev_dax
> > in the event that a memory failure is detected.
> >
> > When a file access resolves to a daxdev with memory errors, it will fail
> > with an appropriate error.
> >
> > If a daxdev failed fs_dax_get(), we set dd->dax_err. If a daxdev called
> > our notify_failure(), set dd->error. When any of the above happens, set
> > (file)->error and stop allowing access.
> >
> > In general, the recovery from memory errors is to unmount the file
> > system and re-initialize the memory, but there may be usable degraded
> > modes of operation - particularly in the future when famfs supports
> > file systems backed by more than one daxdev. In those cases,
> > accessing data that is on a working daxdev can still work.
> >
> > For now, return errors for any file that has encountered a memory or dax
> > error.
> >
> > Signed-off-by: John Groves <[email protected]>
> > ---
> > fs/fuse/famfs.c | 115 +++++++++++++++++++++++++++++++++++++++---
> > fs/fuse/famfs_kfmap.h | 3 +-
> > 2 files changed, 109 insertions(+), 9 deletions(-)
> >
> > diff --git a/fs/fuse/famfs.c b/fs/fuse/famfs.c
> > index c02b14789c6e..4eb87c5c628e 100644
> > --- a/fs/fuse/famfs.c
> > +++ b/fs/fuse/famfs.c
>
> > @@ -254,6 +288,38 @@ famfs_update_daxdev_table(
> > return 0;
> > }
> >
> > +static void
> > +famfs_set_daxdev_err(
> > + struct fuse_conn *fc,
> > + struct dax_device *dax_devp)
> > +{
> > + int i;
> > +
> > + /* Gotta search the list by dax_devp;
> > + * read lock because we're not adding or removing daxdev entries
> > + */
> > + down_read(&fc->famfs_devlist_sem);
>
> Use a guard()
Done
>
> > + for (i = 0; i < fc->dax_devlist->nslots; i++) {
> > + if (fc->dax_devlist->devlist[i].valid) {
> > + struct famfs_daxdev *dd = &fc->dax_devlist->devlist[i];
> > +
> > + if (dd->devp != dax_devp)
> > + continue;
> > +
> > + dd->error = true;
> > + up_read(&fc->famfs_devlist_sem);
> > +
> > + pr_err("%s: memory error on daxdev %s (%d)\n",
> > + __func__, dd->name, i);
> > + goto done;
> > + }
> > + }
> > + up_read(&fc->famfs_devlist_sem);
> > + pr_err("%s: memory err on unrecognized daxdev\n", __func__);
> > +
> > +done:
>
> If this isn't getting more interesting, just return above.
Right - simplified.
>
> > +}
> > +
> >
> > /***************************************************************************/
> >
> > void
> > @@ -611,6 +677,26 @@ famfs_file_init_dax(
> >
> > static ssize_t famfs_file_bad(struct inode *inode);
> >
> > +static int famfs_dax_err(struct famfs_daxdev *dd)
>
> I'd introduce this earlier in the series to reduce need
> to refactor below.
Will mull that over when I further mull the helpers in fuse_i.h that are
hard to rebase...
>
> > +{
> > + if (!dd->valid) {
> > + pr_err("%s: daxdev=%s invalid\n",
> > + __func__, dd->name);
> > + return -EIO;
> > + }
> > + if (dd->dax_err) {
> > + pr_err("%s: daxdev=%s dax_err\n",
> > + __func__, dd->name);
> > + return -EIO;
> > + }
> > + if (dd->error) {
> > + pr_err("%s: daxdev=%s memory error\n",
> > + __func__, dd->name);
> > + return -EHWPOISON;
> > + }
> > + return 0;
> > +}
>
> ...
>
> > @@ -966,7 +1064,8 @@ famfs_file_bad(struct inode *inode)
> > return -EIO;
> > }
> > if (meta->error) {
> > - pr_debug("%s: previously detected metadata errors\n", __func__);
> > + pr_debug("%s: previously detected metadata errors\n",
> > + __func__);
>
> Spurious change.
Derp. Reverted out
Thanks Jonathan
