1 files changed, 102 insertions, 0 deletions
diff --git a/0007-btrfs-refresh-dir-last-index-during-a-rewinddir-3-ca.patch b/0007-btrfs-refresh-dir-last-index-during-a-rewinddir-3-ca.patch
new file mode 100644
index 000000000000..6218aa7ce847
--- /dev/null
+++ b/0007-btrfs-refresh-dir-last-index-during-a-rewinddir-3-ca.patch
@@ -0,0 +1,102 @@
+From f2e0f18c8bd9c6d61575a2311d488e21831e1163 Mon Sep 17 00:00:00 2001
+From: Filipe Manana <fdmanana@suse.com>
+Date: Sat, 9 Sep 2023 12:12:14 +0100
+Subject: [PATCH 7/8] btrfs: refresh dir last index during a rewinddir(3) call
+
+When opening a directory we find what's the index of its last entry and
+then store it in the directory's file handle private data (struct
+btrfs_file_private::last_index), so that in the case new directory entries
+are added to a directory after an opendir(3) call we don't end up in an
+infinite loop (see commit 9b378f6ad48c ("btrfs: fix infinite directory
+reads")) when calling readdir(3).
+
+However once rewinddir(3) is called, POSIX states [1] that any new
+directory entries added after the previous opendir(3) call, must be
+returned by subsequent calls to readdir(3):
+
+  "The rewinddir() function shall reset the position of the directory
+   stream to which dirp refers to the beginning of the directory.
+   It shall also cause the directory stream to refer to the current
+   state of the corresponding directory, as a call to opendir() would
+   have done."
+
+We currently don't refresh the last_index field of the struct
+btrfs_file_private associated to the directory, so after a rewinddir(3)
+we are not returning any new entries added after the opendir(3) call.
+
+Fix this by finding the current last index of the directory when llseek
+is called agains the directory.
+
+This can be reproduced by the following C program provided by Ian Johnson:
+
+   #include <dirent.h>
+   #include <stdio.h>
+
+   int main(void) {
+     DIR *dir = opendir("test");
+
+     FILE *file;
+     file = fopen("test/1", "w");
+     fwrite("1", 1, 1, file);
+     fclose(file);
+
+     file = fopen("test/2", "w");
+     fwrite("2", 1, 1, file);
+     fclose(file);
+
+     rewinddir(dir);
+
+     struct dirent *entry;
+     while ((entry = readdir(dir))) {
+        printf("%s\n", entry->d_name);
+     }
+     closedir(dir);
+     return 0;
+   }
+
+[1] https://pubs.opengroup.org/onlinepubs/9699919799/functions/rewinddir.html
+
+Reported-by: Ian Johnson <ian@ianjohnson.dev>
+Link: https://lore.kernel.org/linux-btrfs/YR1P0S.NGASEG570GJ8@ianjohnson.dev/
+Fixes: 9b378f6ad48c ("btrfs: fix infinite directory reads")
+Signed-off-by: Filipe Manana <fdmanana@suse.com>
+---
+ fs/btrfs/inode.c | 15 ++++++++++++++-
+ 1 file changed, 14 insertions(+), 1 deletion(-)
+
+diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
+index e3a52438f4f1f..a50cbcafca03c 100644
+--- a/fs/btrfs/inode.c
++++ b/fs/btrfs/inode.c
+@@ -5973,6 +5973,19 @@ static int btrfs_opendir(struct inode *inode, struct file *file)
+ 	return 0;
+ }
+ 
++static loff_t btrfs_dir_llseek(struct file *file, loff_t offset, int whence)
++{
++	struct btrfs_file_private *private = file->private_data;
++	int ret;
++
++	ret = btrfs_get_dir_last_index(BTRFS_I(file_inode(file)),
++				       &private->last_index);
++	if (ret)
++		return ret;
++
++	return generic_file_llseek(file, offset, whence);
++}
++
+ struct dir_entry {
+ 	u64 ino;
+ 	u64 offset;
+@@ -11053,7 +11066,7 @@ static const struct inode_operations btrfs_dir_inode_operations = {
+ };
+ 
+ static const struct file_operations btrfs_dir_file_operations = {
+-	.llseek		= generic_file_llseek,
++	.llseek		= btrfs_dir_llseek,
+ 	.read		= generic_read_dir,
+ 	.iterate_shared	= btrfs_real_readdir,
+ 	.open		= btrfs_opendir,
+-- 
+2.41.0
+