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@xxxxxxxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
---
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 */
--
2.43.5
