Re: [syzbot] [v9fs?] WARNING in v9fs_begin_writeback

[Edward Adam Davis <eadavis@qq.com>]

debug

#syz test: upstream c0ecd6388360

diff --git a/mm/filemap.c b/mm/filemap.c
index d62150418b91..5112cf69bce2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -394,6 +394,7 @@ int filemap_fdatawrite_wbc(struct address_space *mapping,
 		return 0;
 
 	wbc_attach_fdatawrite_inode(wbc, mapping->host);
+	printk("ino: %lx, comm: %s, %s\n", mapping->host->i_ino, current->comm, __func__);
 	ret = do_writepages(mapping, wbc);
 	wbc_detach_inode(wbc);
 	return ret;
@@ -427,17 +428,20 @@ int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 		.range_end = end,
 	};
 
+	printk("ino: %lx, comm: %s, %s\n", mapping->host->i_ino, current->comm, __func__);
 	return filemap_fdatawrite_wbc(mapping, &wbc);
 }
 
 static inline int __filemap_fdatawrite(struct address_space *mapping,
 	int sync_mode)
 {
+	printk("ino: %lx, comm: %s, %s\n", mapping->host->i_ino, current->comm, __func__);
 	return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
 }
 
 int filemap_fdatawrite(struct address_space *mapping)
 {
+	printk("ino: %lx, comm: %s, %s\n", mapping->host->i_ino, current->comm, __func__);
 	return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
 }
 EXPORT_SYMBOL(filemap_fdatawrite);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 4430ac68e4c4..f76ce90a5396 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2687,6 +2687,7 @@ int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
 			/* deal with chardevs and other special files */
 			ret = 0;
 		}
+		printk("ret: %d, ino: %lx, comm: %s, %s\n", ret, mapping->host->i_ino, current->comm, __func__);
 		if (ret != -ENOMEM || wbc->sync_mode != WB_SYNC_ALL)
 			break;
 
diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index a97ceb105cd8..7768cc70439d 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -34,6 +34,7 @@ static void v9fs_begin_writeback(struct netfs_io_request *wreq)
 {
 	struct p9_fid *fid;
 
+	printk("ino: %lx, %s\n", wreq->inode->i_ino, __func__);
 	fid = v9fs_fid_find_inode(wreq->inode, true, INVALID_UID, true);
 	if (!fid) {
 		WARN_ONCE(1, "folio expected an open fid inode->i_ino=%lx\n",
diff --git a/fs/9p/vfs_dir.c b/fs/9p/vfs_dir.c
index e0d34e4e9076..2705474f5fcb 100644
--- a/fs/9p/vfs_dir.c
+++ b/fs/9p/vfs_dir.c
@@ -215,10 +215,13 @@ int v9fs_dir_release(struct inode *inode, struct file *filp)
 		 inode, filp, fid ? fid->fid : -1);
 
 	if (fid) {
-		if ((S_ISREG(inode->i_mode)) && (filp->f_mode & FMODE_WRITE))
+		if ((S_ISREG(inode->i_mode)) && (filp->f_mode & FMODE_WRITE)) {
+			printk("ino: %lx, comm: %s, %s\n", inode->i_ino, current->comm, __func__);
 			retval = filemap_fdatawrite(inode->i_mapping);
+		}
 
 		spin_lock(&inode->i_lock);
+		printk("del, ino: %lx, ino sync: %d, comm: %s, %s\n", inode->i_ino, inode->i_state & I_SYNC, current->comm, __func__);
 		hlist_del(&fid->ilist);
 		spin_unlock(&inode->i_lock);
 		put_err = p9_fid_put(fid);
diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 348cc90bf9c5..a3c32b7de2f5 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -44,6 +44,7 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 	struct p9_fid *fid;
 	int omode;
 
+	pr_info("ino: %lx, %s\n", inode->i_ino, __func__);
 	p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, file);
 	v9ses = v9fs_inode2v9ses(inode);
 	if (v9fs_proto_dotl(v9ses))
@@ -461,6 +462,7 @@ v9fs_file_mmap(struct file *filp, struct vm_area_struct *vma)
 	struct v9fs_session_info *v9ses = v9fs_inode2v9ses(inode);
 
 	p9_debug(P9_DEBUG_MMAP, "filp :%p\n", filp);
+	pr_info("ino: %lx, comm: %s, %s\n", inode->i_ino, current->comm, __func__);
 
 	if (!(v9ses->cache & CACHE_WRITEBACK)) {
 		p9_debug(P9_DEBUG_CACHE, "(read-only mmap mode)");
@@ -477,6 +479,7 @@ v9fs_file_mmap(struct file *filp, struct vm_area_struct *vma)
 static vm_fault_t
 v9fs_vm_page_mkwrite(struct vm_fault *vmf)
 {
+	printk("comm: %s, %s\n", current->comm, __func__);
 	return netfs_page_mkwrite(vmf, NULL);
 }
 
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index fd72fc38c8f5..99f42ce8de15 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -355,6 +355,7 @@ void v9fs_evict_inode(struct inode *inode)
 		netfs_clear_inode_writeback(inode, &version);
 
 		clear_inode(inode);
+		printk("ino: %lx, comm: %s, %s\n", inode->i_ino, current->comm, __func__);
 		filemap_fdatawrite(&inode->i_data);
 
 #ifdef CONFIG_9P_FSCACHE
@@ -1034,6 +1035,7 @@ static int v9fs_vfs_setattr(struct mnt_idmap *idmap,
 
 	/* Write all dirty data */
 	if (d_is_reg(dentry)) {
+		printk("ino: %lx, comm: %s, %s\n", inode->i_ino, current->comm, __func__);
 		retval = filemap_fdatawrite(inode->i_mapping);
 		if (retval)
 			p9_debug(P9_DEBUG_ERROR,
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index c61b97bd13b9..68b3ced3f3b1 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -518,6 +518,7 @@ int v9fs_vfs_setattr_dotl(struct mnt_idmap *idmap,
 
 	/* Write all dirty data */
 	if (S_ISREG(inode->i_mode)) {
+		printk("ino: %lx, comm: %s, %s\n", inode->i_ino, current->comm, __func__);
 		retval = filemap_fdatawrite(inode->i_mapping);
 		if (retval < 0)
 			p9_debug(P9_DEBUG_ERROR,
diff --git a/fs/netfs/write_issue.c b/fs/netfs/write_issue.c
index 9258d30cffe3..87d14dfa9017 100644
--- a/fs/netfs/write_issue.c
+++ b/fs/netfs/write_issue.c
@@ -35,6 +35,7 @@
 #include <linux/mm.h>
 #include <linux/pagemap.h>
 #include "internal.h"
+#include <linux/backing-dev.h>
 
 /*
  * Kill all dirty folios in the event of an unrecoverable error, starting with
@@ -503,6 +504,15 @@ int netfs_writepages(struct address_space *mapping,
 	struct folio *folio;
 	int error = 0;
 
+	if (!mapping_can_writeback(mapping) ||
+	    !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
+		printk("ino %lx can not wb: %d or mapping tagged :%d, %s\n",
+			mapping->host->i_ino, mapping_can_writeback(mapping),
+			mapping_tagged(mapping, PAGECACHE_TAG_DIRTY),
+			__func__);
+		return 0;
+	}
+
 	if (wbc->sync_mode == WB_SYNC_ALL)
 		mutex_lock(&ictx->wb_lock);
 	else if (!mutex_trylock(&ictx->wb_lock))
@@ -522,6 +532,8 @@ int netfs_writepages(struct address_space *mapping,
 	trace_netfs_write(wreq, netfs_write_trace_writeback);
 	netfs_stat(&netfs_n_wh_writepages);
 
+	printk("ino state: %lu, ino: %lx, comm: %s, folio: %p, %s\n", wreq->inode->i_state,
+			wreq->inode->i_ino, current->comm, folio, __func__);
 	do {
 		_debug("wbiter %lx %llx", folio->index, wreq->start + wreq->submitted);