NFS: Return the file btime in the statx results when appropriate

JIRA: https://issues.redhat.com/browse/RHEL-90990

commit 4b54274
Author: Trond Myklebust <trond.myklebust@hammerspace.com>
Date:   Thu May 29 06:45:47 2025 -0400

    NFS: Return the file btime in the statx results when appropriate

    If the server supports the NFSv4.x "create_time" attribute, then return
    it as part of the statx results.

    Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
    Reviewed-by: Jeff Layton <jlayton@kernel.org>
    Link: https://lore.kernel.org/r/eae27d6467e08aaa67e0ac6ae7119263a0f83349.1748515333.git.bcodding@redhat.com
    Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>

Author: bcodding-rh

fs/nfs/inode.c

@@ -891,6 +891,7 @@ static void nfs_readdirplus_parent_cache_hit(struct dentry *dentry)
 
 static u32 nfs_get_valid_attrmask(struct inode *inode)
 {
+	u64 fattr_valid = NFS_SERVER(inode)->fattr_valid;
 	unsigned long cache_validity = READ_ONCE(NFS_I(inode)->cache_validity);
 	u32 reply_mask = STATX_INO | STATX_TYPE;
 
@@ -910,6 +911,9 @@ static u32 nfs_get_valid_attrmask(struct inode *inode)
 		reply_mask |= STATX_UID | STATX_GID;
 	if (!(cache_validity & NFS_INO_INVALID_BLOCKS))
 		reply_mask |= STATX_BLOCKS;
+	if (!(cache_validity & NFS_INO_INVALID_BTIME) &&
+	    (fattr_valid & NFS_ATTR_FATTR_BTIME))
+		reply_mask |= STATX_BTIME;
 	if (!(cache_validity & NFS_INO_INVALID_CHANGE))
 		reply_mask |= STATX_CHANGE_COOKIE;
 	return reply_mask;
@@ -920,6 +924,7 @@ int nfs_getattr(struct mnt_idmap *idmap, const struct path *path,
 {
 	struct inode *inode = d_inode(path->dentry);
 	struct nfs_server *server = NFS_SERVER(inode);
+	u64 fattr_valid = server->fattr_valid;
 	unsigned long cache_validity;
 	int err = 0;
 	bool force_sync = query_flags & AT_STATX_FORCE_SYNC;
@@ -930,9 +935,12 @@ int nfs_getattr(struct mnt_idmap *idmap, const struct path *path,
 
 	request_mask &= STATX_TYPE | STATX_MODE | STATX_NLINK | STATX_UID |
 			STATX_GID | STATX_ATIME | STATX_MTIME | STATX_CTIME |
-			STATX_INO | STATX_SIZE | STATX_BLOCKS |
+			STATX_INO | STATX_SIZE | STATX_BLOCKS | STATX_BTIME |
 			STATX_CHANGE_COOKIE;
 
+	if (!(fattr_valid & NFS_ATTR_FATTR_BTIME))
+		request_mask &= ~STATX_BTIME;
+
 	if ((query_flags & AT_STATX_DONT_SYNC) && !force_sync) {
 		if (readdirplus_enabled)
 			nfs_readdirplus_parent_cache_hit(path->dentry);
@@ -964,7 +972,7 @@ int nfs_getattr(struct mnt_idmap *idmap, const struct path *path,
 	/* Is the user requesting attributes that might need revalidation? */
 	if (!(request_mask & (STATX_MODE|STATX_NLINK|STATX_ATIME|STATX_CTIME|
 					STATX_MTIME|STATX_UID|STATX_GID|
-					STATX_SIZE|STATX_BLOCKS|
+					STATX_SIZE|STATX_BLOCKS|STATX_BTIME|
 					STATX_CHANGE_COOKIE)))
 		goto out_no_revalidate;
 
@@ -988,6 +996,8 @@ int nfs_getattr(struct mnt_idmap *idmap, const struct path *path,
 		do_update |= cache_validity & NFS_INO_INVALID_OTHER;
 	if (request_mask & STATX_BLOCKS)
 		do_update |= cache_validity & NFS_INO_INVALID_BLOCKS;
+	if (request_mask & STATX_BTIME)
+		do_update |= cache_validity & NFS_INO_INVALID_BTIME;
 
 	if (do_update) {
 		if (readdirplus_enabled)
@@ -1009,6 +1019,7 @@ int nfs_getattr(struct mnt_idmap *idmap, const struct path *path,
 		stat->attributes |= STATX_ATTR_CHANGE_MONOTONIC;
 	if (S_ISDIR(inode->i_mode))
 		stat->blksize = NFS_SERVER(inode)->dtsize;
+	stat->btime = NFS_I(inode)->btime;
 out:
 	trace_nfs_getattr_exit(inode, err);
 	return err;

fs/nfs/nfs4trace.h

@@ -30,7 +30,8 @@
 		{ NFS_ATTR_FATTR_CTIME, "CTIME" }, \
 		{ NFS_ATTR_FATTR_CHANGE, "CHANGE" }, \
 		{ NFS_ATTR_FATTR_OWNER_NAME, "OWNER_NAME" }, \
-		{ NFS_ATTR_FATTR_GROUP_NAME, "GROUP_NAME" })
+		{ NFS_ATTR_FATTR_GROUP_NAME, "GROUP_NAME" }, \
+		{ NFS_ATTR_FATTR_BTIME, "BTIME" })
 
 DECLARE_EVENT_CLASS(nfs4_clientid_event,
 		TP_PROTO(