| Message ID | 20240627100129.2482408-1-dan.aloni@vastdata.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | nfs: add 'noalignwrite' option for lock-less 'lost writes' prevention | expand |
On Thu, 2024-06-27 at 13:01 +0300, Dan Aloni wrote: > There are some applications that write to predefined non-overlapping > file offsets from multiple clients and therefore don't need to rely > on > file locking. However, if these applications want non-aligned offsets > and sizes they need to either use locks or risk data corruption, as > the > NFS client defaults to extending writes to whole pages. > > This commit adds a new mount option `noalignwrite`, which allows to > turn > that off and avoid the need of locking, as long as these applications > don't overlap on offsets. > > Signed-off-by: Dan Aloni <dan.aloni@vastdata.com> > --- > fs/nfs/fs_context.c | 8 ++++++++ > fs/nfs/super.c | 3 +++ > fs/nfs/write.c | 3 +++ > include/linux/nfs_fs_sb.h | 1 + > 4 files changed, 15 insertions(+) > > diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c > index 6c9f3f6645dd..7e000d782e28 100644 > --- a/fs/nfs/fs_context.c > +++ b/fs/nfs/fs_context.c > @@ -49,6 +49,7 @@ enum nfs_param { > Opt_bsize, > Opt_clientaddr, > Opt_cto, > + Opt_alignwrite, > Opt_fg, > Opt_fscache, > Opt_fscache_flag, > @@ -149,6 +150,7 @@ static const struct fs_parameter_spec > nfs_fs_parameters[] = { > fsparam_u32 ("bsize", Opt_bsize), > fsparam_string("clientaddr", Opt_clientaddr), > fsparam_flag_no("cto", Opt_cto), > + fsparam_flag_no("alignwrite", Opt_alignwrite), > fsparam_flag ("fg", Opt_fg), > fsparam_flag_no("fsc", Opt_fscache_flag), > fsparam_string("fsc", Opt_fscache), > @@ -592,6 +594,12 @@ static int nfs_fs_context_parse_param(struct > fs_context *fc, > else > ctx->flags |= NFS_MOUNT_TRUNK_DISCOVERY; > break; > + case Opt_alignwrite: > + if (result.negated) > + ctx->flags |= NFS_MOUNT_NO_ALIGNWRITE; > + else > + ctx->flags &= ~NFS_MOUNT_NO_ALIGNWRITE; > + break; > case Opt_ac: > if (result.negated) > ctx->flags |= NFS_MOUNT_NOAC; > diff --git a/fs/nfs/super.c b/fs/nfs/super.c > index cbbd4866b0b7..1382ae19bba4 100644 > --- a/fs/nfs/super.c > +++ b/fs/nfs/super.c > @@ -549,6 +549,9 @@ static void nfs_show_mount_options(struct > seq_file *m, struct nfs_server *nfss, > else > seq_puts(m, ",local_lock=posix"); > > + if (nfss->flags & NFS_MOUNT_NO_ALIGNWRITE) > + seq_puts(m, ",noalignwrite"); > + > if (nfss->flags & NFS_MOUNT_WRITE_EAGER) { > if (nfss->flags & NFS_MOUNT_WRITE_WAIT) > seq_puts(m, ",write=wait"); > diff --git a/fs/nfs/write.c b/fs/nfs/write.c > index 2329cbb0e446..cfe8061bf005 100644 > --- a/fs/nfs/write.c > +++ b/fs/nfs/write.c > @@ -1315,7 +1315,10 @@ static int nfs_can_extend_write(struct file > *file, struct folio *folio, > struct file_lock_context *flctx = > locks_inode_context(inode); > struct file_lock *fl; > int ret; > + unsigned int mntflags = NFS_SERVER(inode)->flags; > > + if (mntflags & NFS_MOUNT_NO_ALIGNWRITE) > + return 0; > if (file->f_flags & O_DSYNC) > return 0; > if (!nfs_folio_write_uptodate(folio, pagelen)) > diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h > index 92de074e63b9..4d28b4a328a7 100644 > --- a/include/linux/nfs_fs_sb.h > +++ b/include/linux/nfs_fs_sb.h > @@ -157,6 +157,7 @@ struct nfs_server { > #define NFS_MOUNT_WRITE_WAIT 0x02000000 > #define NFS_MOUNT_TRUNK_DISCOVERY 0x04000000 > #define NFS_MOUNT_SHUTDOWN 0x08000000 > +#define NFS_MOUNT_NO_ALIGNWRITE 0x10000000 > > unsigned int fattr_valid; /* Valid attributes > */ > unsigned int caps; /* server > capabilities */ While I hate that we need a new mount option for this, I do understand the need. I do wonder if we'd be better served by a new fadvise64() flag or something. Either way, this would probably be needed in the interim, so... Reviewed-by: Jeff Layton <jlayton@kernel.org>
On 27/06/2024 13:01, Dan Aloni wrote: > There are some applications that write to predefined non-overlapping > file offsets from multiple clients and therefore don't need to rely on > file locking. However, if these applications want non-aligned offsets > and sizes they need to either use locks or risk data corruption, as the > NFS client defaults to extending writes to whole pages. > > This commit adds a new mount option `noalignwrite`, which allows to turn > that off and avoid the need of locking, as long as these applications > don't overlap on offsets. > > Signed-off-by: Dan Aloni <dan.aloni@vastdata.com> The new name seems a better choice. I'm also on Christoph's camp that having this behavior be the default makes sense given that we have large folios. Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Trond, Anna, What are your thoughts on this?
On 2024-07-03 22:09:58, Sagi Grimberg wrote: > > > On 27/06/2024 13:01, Dan Aloni wrote: > > There are some applications that write to predefined non-overlapping > > file offsets from multiple clients and therefore don't need to rely on > > file locking. However, if these applications want non-aligned offsets > > and sizes they need to either use locks or risk data corruption, as the > > NFS client defaults to extending writes to whole pages. > > > > This commit adds a new mount option `noalignwrite`, which allows to turn > > that off and avoid the need of locking, as long as these applications > > don't overlap on offsets. > > > > Signed-off-by: Dan Aloni <dan.aloni@vastdata.com> > > The new name seems a better choice. > I'm also on Christoph's camp that having this behavior be the default makes > sense given that we have large folios. > > Reviewed-by: Sagi Grimberg <sagi@grimberg.me> > > > Trond, Anna, > What are your thoughts on this? Pinging. Do we need to do anything further? I can prepare the nfs-utils patch too.
diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c index 6c9f3f6645dd..7e000d782e28 100644 --- a/fs/nfs/fs_context.c +++ b/fs/nfs/fs_context.c @@ -49,6 +49,7 @@ enum nfs_param { Opt_bsize, Opt_clientaddr, Opt_cto, + Opt_alignwrite, Opt_fg, Opt_fscache, Opt_fscache_flag, @@ -149,6 +150,7 @@ static const struct fs_parameter_spec nfs_fs_parameters[] = { fsparam_u32 ("bsize", Opt_bsize), fsparam_string("clientaddr", Opt_clientaddr), fsparam_flag_no("cto", Opt_cto), + fsparam_flag_no("alignwrite", Opt_alignwrite), fsparam_flag ("fg", Opt_fg), fsparam_flag_no("fsc", Opt_fscache_flag), fsparam_string("fsc", Opt_fscache), @@ -592,6 +594,12 @@ static int nfs_fs_context_parse_param(struct fs_context *fc, else ctx->flags |= NFS_MOUNT_TRUNK_DISCOVERY; break; + case Opt_alignwrite: + if (result.negated) + ctx->flags |= NFS_MOUNT_NO_ALIGNWRITE; + else + ctx->flags &= ~NFS_MOUNT_NO_ALIGNWRITE; + break; case Opt_ac: if (result.negated) ctx->flags |= NFS_MOUNT_NOAC; diff --git a/fs/nfs/super.c b/fs/nfs/super.c index cbbd4866b0b7..1382ae19bba4 100644 --- a/fs/nfs/super.c +++ b/fs/nfs/super.c @@ -549,6 +549,9 @@ static void nfs_show_mount_options(struct seq_file *m, struct nfs_server *nfss, else seq_puts(m, ",local_lock=posix"); + if (nfss->flags & NFS_MOUNT_NO_ALIGNWRITE) + seq_puts(m, ",noalignwrite"); + if (nfss->flags & NFS_MOUNT_WRITE_EAGER) { if (nfss->flags & NFS_MOUNT_WRITE_WAIT) seq_puts(m, ",write=wait"); diff --git a/fs/nfs/write.c b/fs/nfs/write.c index 2329cbb0e446..cfe8061bf005 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -1315,7 +1315,10 @@ static int nfs_can_extend_write(struct file *file, struct folio *folio, struct file_lock_context *flctx = locks_inode_context(inode); struct file_lock *fl; int ret; + unsigned int mntflags = NFS_SERVER(inode)->flags; + if (mntflags & NFS_MOUNT_NO_ALIGNWRITE) + return 0; if (file->f_flags & O_DSYNC) return 0; if (!nfs_folio_write_uptodate(folio, pagelen)) diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h index 92de074e63b9..4d28b4a328a7 100644 --- a/include/linux/nfs_fs_sb.h +++ b/include/linux/nfs_fs_sb.h @@ -157,6 +157,7 @@ struct nfs_server { #define NFS_MOUNT_WRITE_WAIT 0x02000000 #define NFS_MOUNT_TRUNK_DISCOVERY 0x04000000 #define NFS_MOUNT_SHUTDOWN 0x08000000 +#define NFS_MOUNT_NO_ALIGNWRITE 0x10000000 unsigned int fattr_valid; /* Valid attributes */ unsigned int caps; /* server capabilities */
There are some applications that write to predefined non-overlapping file offsets from multiple clients and therefore don't need to rely on file locking. However, if these applications want non-aligned offsets and sizes they need to either use locks or risk data corruption, as the NFS client defaults to extending writes to whole pages. This commit adds a new mount option `noalignwrite`, which allows to turn that off and avoid the need of locking, as long as these applications don't overlap on offsets. Signed-off-by: Dan Aloni <dan.aloni@vastdata.com> --- fs/nfs/fs_context.c | 8 ++++++++ fs/nfs/super.c | 3 +++ fs/nfs/write.c | 3 +++ include/linux/nfs_fs_sb.h | 1 + 4 files changed, 15 insertions(+)