Patch "nfsd: allow reaping files still under writeback" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    nfsd: allow reaping files still under writeback

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nfsd-allow-reaping-files-still-under-writeback.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 4359feeab74beb1053183e09213ddf6400c565f1
Author: Jeff Layton <jlayton@xxxxxxxxxx>
Date:   Wed Feb 15 06:53:54 2023 -0500

    nfsd: allow reaping files still under writeback
    
    [ Upstream commit dcb779fcd4ed5984ad15991d574943d12a8693d1 ]
    
    On most filesystems, there is no reason to delay reaping an nfsd_file
    just because its underlying inode is still under writeback. nfsd just
    relies on client activity or the local flusher threads to do writeback.
    
    The main exception is NFS, which flushes all of its dirty data on last
    close. Add a new EXPORT_OP_FLUSH_ON_CLOSE flag to allow filesystems to
    signal that they do this, and only skip closing files under writeback on
    such filesystems.
    
    Also, remove a redundant NULL file pointer check in
    nfsd_file_check_writeback, and clean up nfs's export op flag
    definitions.
    
    Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
    Acked-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
    [ cel: adjusted to apply to v5.15.y ]
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>

diff --git a/fs/nfs/export.c b/fs/nfs/export.c
index 37a1a88df7717..eafa9d7b0911b 100644
--- a/fs/nfs/export.c
+++ b/fs/nfs/export.c
@@ -178,7 +178,10 @@ const struct export_operations nfs_export_ops = {
 	.fh_to_dentry = nfs_fh_to_dentry,
 	.get_parent = nfs_get_parent,
 	.fetch_iversion = nfs_fetch_iversion,
-	.flags = EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK|
-		EXPORT_OP_CLOSE_BEFORE_UNLINK|EXPORT_OP_REMOTE_FS|
-		EXPORT_OP_NOATOMIC_ATTR,
+	.flags = EXPORT_OP_NOWCC		|
+		 EXPORT_OP_NOSUBTREECHK		|
+		 EXPORT_OP_CLOSE_BEFORE_UNLINK	|
+		 EXPORT_OP_REMOTE_FS		|
+		 EXPORT_OP_NOATOMIC_ATTR	|
+		 EXPORT_OP_FLUSH_ON_CLOSE,
 };
diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 1d4c0387c4192..080d796547854 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -401,13 +401,23 @@ nfsd_file_check_writeback(struct nfsd_file *nf)
 	struct file *file = nf->nf_file;
 	struct address_space *mapping;
 
-	if (!file || !(file->f_mode & FMODE_WRITE))
+	/* File not open for write? */
+	if (!(file->f_mode & FMODE_WRITE))
 		return false;
+
+	/*
+	 * Some filesystems (e.g. NFS) flush all dirty data on close.
+	 * On others, there is no need to wait for writeback.
+	 */
+	if (!(file_inode(file)->i_sb->s_export_op->flags & EXPORT_OP_FLUSH_ON_CLOSE))
+		return false;
+
 	mapping = file->f_mapping;
 	return mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) ||
 		mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK);
 }
 
+
 static bool nfsd_file_lru_add(struct nfsd_file *nf)
 {
 	set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags);
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index fe848901fcc3a..218fc5c54e901 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -221,6 +221,7 @@ struct export_operations {
 #define EXPORT_OP_NOATOMIC_ATTR		(0x10) /* Filesystem cannot supply
 						  atomic attribute updates
 						*/
+#define EXPORT_OP_FLUSH_ON_CLOSE	(0x20) /* fs flushes file data on close */
 	unsigned long	flags;
 };