Should BUG() be removed or changed to WARN_ON in iov_iter changeset

[Steve French <smfrench@gmail.com>]

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/home/smfrench/dhowell/linux-fs/0003-cifs-Add-some-helper-functions.patch
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WARNING: Avoid crashing the kernel - try using WARN_ON & recovery code
rather than BUG() or BUG_ON()
#67: FILE: fs/cifs/cifssmb.c:1950:
+ BUG();

WARNING: Avoid crashing the kernel - try using WARN_ON & recovery code
rather than BUG() or BUG_ON()
#95: FILE: fs/cifs/cifssmb.c:1978:
+ BUG();

WARNING: Avoid crashing the kernel - try using WARN_ON & recovery code
rather than BUG() or BUG_ON()
#123: FILE: fs/cifs/cifssmb.c:2006:
+ BUG();

total: 0 errors, 3 warnings, 106 lines checked


-- 
Thanks,

Steve

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From 99b3366e40c61642efbd953022aec76cf791eca9 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Wed, 6 Apr 2022 19:41:28 +0100
Subject: [PATCH 3/7] cifs: Add some helper functions

Add some helper functions to manipulate the folio marks by iterating
through a list of folios held in an xarray rather than using a page list.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: Rohith Surabattula <rohiths.msft@gmail.com>
cc: linux-cifs@vger.kernel.org
---
 fs/cifs/cifsfs.h  |  3 ++
 fs/cifs/cifssmb.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 88 insertions(+)

diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index c0542bdcd06b..34ad965cde21 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -110,6 +110,9 @@ extern int cifs_file_strict_mmap(struct file * , struct vm_area_struct *);
 extern const struct file_operations cifs_dir_ops;
 extern int cifs_dir_open(struct inode *inode, struct file *file);
 extern int cifs_readdir(struct file *file, struct dir_context *ctx);
+extern void cifs_pages_written_back(struct inode *inode, loff_t start, unsigned int len);
+extern void cifs_pages_write_failed(struct inode *inode, loff_t start, unsigned int len);
+extern void cifs_pages_write_redirty(struct inode *inode, loff_t start, unsigned int len);
 
 /* Functions related to dir entries */
 extern const struct dentry_operations cifs_dentry_ops;
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 47e927c4ff8d..88e2de74f74f 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -27,6 +27,7 @@
 #include "cifsglob.h"
 #include "cifsacl.h"
 #include "cifsproto.h"
+#include "cifsfs.h"
 #include "cifs_unicode.h"
 #include "cifs_debug.h"
 #include "smb2proto.h"
@@ -1928,6 +1929,90 @@ cifs_writedata_release(struct kref *refcount)
 	kfree(wdata);
 }
 
+/*
+ * Completion of write to server.
+ */
+void cifs_pages_written_back(struct inode *inode, loff_t start, unsigned int len)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct folio *folio;
+	pgoff_t end;
+
+	XA_STATE(xas, &mapping->i_pages, start / PAGE_SIZE);
+
+	rcu_read_lock();
+
+	end = (start + len - 1) / PAGE_SIZE;
+	xas_for_each(&xas, folio, end) {
+		if (!folio_test_writeback(folio)) {
+			pr_err("bad %x @%llx page %lx %lx\n",
+			       len, start, folio_index(folio), end);
+			BUG();
+		}
+
+		folio_detach_private(folio);
+		folio_end_writeback(folio);
+	}
+
+	rcu_read_unlock();
+}
+
+/*
+ * Failure of write to server.
+ */
+void cifs_pages_write_failed(struct inode *inode, loff_t start, unsigned int len)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct folio *folio;
+	pgoff_t end;
+
+	XA_STATE(xas, &mapping->i_pages, start / PAGE_SIZE);
+
+	rcu_read_lock();
+
+	end = (start + len - 1) / PAGE_SIZE;
+	xas_for_each(&xas, folio, end) {
+		if (!folio_test_writeback(folio)) {
+			pr_err("bad %x @%llx page %lx %lx\n",
+			       len, start, folio_index(folio), end);
+			BUG();
+		}
+
+		folio_set_error(folio);
+		folio_end_writeback(folio);
+	}
+
+	rcu_read_unlock();
+}
+
+/*
+ * Redirty pages after a temporary failure.
+ */
+void cifs_pages_write_redirty(struct inode *inode, loff_t start, unsigned int len)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct folio *folio;
+	pgoff_t end;
+
+	XA_STATE(xas, &mapping->i_pages, start / PAGE_SIZE);
+
+	rcu_read_lock();
+
+	end = (start + len - 1) / PAGE_SIZE;
+	xas_for_each(&xas, folio, end) {
+		if (!folio_test_writeback(folio)) {
+			pr_err("bad %x @%llx page %lx %lx\n",
+			       len, start, folio_index(folio), end);
+			BUG();
+		}
+
+		filemap_dirty_folio(folio->mapping, folio);
+		folio_end_writeback(folio);
+	}
+
+	rcu_read_unlock();
+}
+
 /*
  * Write failed with a retryable error. Resend the write request. It's also
  * possible that the page was redirtied so re-clean the page.
-- 
2.34.1