0050-Revert-ext4-do-not-create-EA-inode-under-buffer-lock.patch

From c13c0e90c89beccfc740aad680f324c1aa6da590 Mon Sep 17 00:00:00 2001
From: Colin Ian King <colin.i.king@intel.com>
Date: Thu, 24 Oct 2024 12:11:04 +0100
Subject: [PATCH] Revert "ext4: do not create EA inode under buffer lock"

Currenlty this commit makes it much easier to hit an ABBA lock
bug, so reverting it reduces this risk, even though it's not
a final solution.

See: https://bugzilla.kernel.org/show_bug.cgi?id=219283

This reverts commit 0a46ef234756dca04623b7591e8ebb3440622f0b.
---
 fs/ext4/xattr.c | 113 +++++++++++++++++++++++++-----------------------
 1 file changed, 60 insertions(+), 53 deletions(-)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 46ce2f21fef9..d2feef9793d0 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1625,7 +1625,6 @@ static struct inode *ext4_xattr_inode_lookup_create(handle_t *handle,
 static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
 				struct ext4_xattr_search *s,
 				handle_t *handle, struct inode *inode,
-				struct inode *new_ea_inode,
 				bool is_block)
 {
 	struct ext4_xattr_entry *last, *next;
@@ -1633,6 +1632,7 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
 	size_t min_offs = s->end - s->base, name_len = strlen(i->name);
 	int in_inode = i->in_inode;
 	struct inode *old_ea_inode = NULL;
+	struct inode *new_ea_inode = NULL;
 	size_t old_size, new_size;
 	int ret;
 
@@ -1717,11 +1717,38 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
 			old_ea_inode = NULL;
 			goto out;
 		}
+	}
+	if (i->value && in_inode) {
+		WARN_ON_ONCE(!i->value_len);
+
+		new_ea_inode = ext4_xattr_inode_lookup_create(handle, inode,
+					i->value, i->value_len);
+		if (IS_ERR(new_ea_inode)) {
+			ret = PTR_ERR(new_ea_inode);
+			new_ea_inode = NULL;
+			goto out;
+		}
+	}
 
+	if (old_ea_inode) {
 		/* We are ready to release ref count on the old_ea_inode. */
 		ret = ext4_xattr_inode_dec_ref(handle, old_ea_inode);
-		if (ret)
+		if (ret) {
+			/* Release newly required ref count on new_ea_inode. */
+			if (new_ea_inode) {
+				int err;
+
+				err = ext4_xattr_inode_dec_ref(handle,
+							       new_ea_inode);
+				if (err)
+					ext4_warning_inode(new_ea_inode,
+						  "dec ref new_ea_inode err=%d",
+						  err);
+				ext4_xattr_inode_free_quota(inode, new_ea_inode,
+							    i->value_len);
+			}
 			goto out;
+		}
 
 		ext4_xattr_inode_free_quota(inode, old_ea_inode,
 					    le32_to_cpu(here->e_value_size));
@@ -1845,6 +1872,7 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i,
 	ret = 0;
 out:
 	iput(old_ea_inode);
+	iput(new_ea_inode);
 	return ret;
 }
 
@@ -1907,20 +1935,8 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 	size_t old_ea_inode_quota = 0;
 	unsigned int ea_ino;
 
-#define header(x) ((struct ext4_xattr_header *)(x))
-
-	/* If we need EA inode, prepare it before locking the buffer */
-	if (i->value && i->in_inode) {
-		WARN_ON_ONCE(!i->value_len);
 
-		ea_inode = ext4_xattr_inode_lookup_create(handle, inode,
-					i->value, i->value_len);
-		if (IS_ERR(ea_inode)) {
-			error = PTR_ERR(ea_inode);
-			ea_inode = NULL;
-			goto cleanup;
-		}
-	}
+#define header(x) ((struct ext4_xattr_header *)(x))
 
 	if (s->base) {
 		int offset = (char *)s->here - bs->bh->b_data;
@@ -1930,7 +1946,6 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 						      EXT4_JTR_NONE);
 		if (error)
 			goto cleanup;
-
 		lock_buffer(bs->bh);
 
 		if (header(s->base)->h_refcount == cpu_to_le32(1)) {
@@ -1957,7 +1972,7 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 			}
 			ea_bdebug(bs->bh, "modifying in-place");
 			error = ext4_xattr_set_entry(i, s, handle, inode,
-					     ea_inode, true /* is_block */);
+						     true /* is_block */);
 			ext4_xattr_block_csum_set(inode, bs->bh);
 			unlock_buffer(bs->bh);
 			if (error == -EFSCORRUPTED)
@@ -2025,13 +2040,29 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 		s->end = s->base + sb->s_blocksize;
 	}
 
-	error = ext4_xattr_set_entry(i, s, handle, inode, ea_inode,
-				     true /* is_block */);
+	error = ext4_xattr_set_entry(i, s, handle, inode, true /* is_block */);
 	if (error == -EFSCORRUPTED)
 		goto bad_block;
 	if (error)
 		goto cleanup;
 
+	if (i->value && s->here->e_value_inum) {
+		/*
+		 * A ref count on ea_inode has been taken as part of the call to
+		 * ext4_xattr_set_entry() above. We would like to drop this
+		 * extra ref but we have to wait until the xattr block is
+		 * initialized and has its own ref count on the ea_inode.
+		 */
+		ea_ino = le32_to_cpu(s->here->e_value_inum);
+		error = ext4_xattr_inode_iget(inode, ea_ino,
+					      le32_to_cpu(s->here->e_hash),
+					      &ea_inode);
+		if (error) {
+			ea_inode = NULL;
+			goto cleanup;
+		}
+	}
+
 inserted:
 	if (!IS_LAST_ENTRY(s->first)) {
 		new_bh = ext4_xattr_block_cache_find(inode, header(s->base), &ce);
@@ -2189,16 +2220,17 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 
 cleanup:
 	if (ea_inode) {
-		if (error) {
-			int error2;
+		int error2;
+
+		error2 = ext4_xattr_inode_dec_ref(handle, ea_inode);
+		if (error2)
+			ext4_warning_inode(ea_inode, "dec ref error=%d",
+					   error2);
 
-			error2 = ext4_xattr_inode_dec_ref(handle, ea_inode);
-			if (error2)
-				ext4_warning_inode(ea_inode, "dec ref error=%d",
-						   error2);
+		/* If there was an error, revert the quota charge. */
+		if (error)
 			ext4_xattr_inode_free_quota(inode, ea_inode,
 						    i_size_read(ea_inode));
-		}
 		iput(ea_inode);
 	}
 	if (ce)
@@ -2256,38 +2288,14 @@ int ext4_xattr_ibody_set(handle_t *handle, struct inode *inode,
 {
 	struct ext4_xattr_ibody_header *header;
 	struct ext4_xattr_search *s = &is->s;
-	struct inode *ea_inode = NULL;
 	int error;
 
 	if (!EXT4_INODE_HAS_XATTR_SPACE(inode))
 		return -ENOSPC;
 
-	/* If we need EA inode, prepare it before locking the buffer */
-	if (i->value && i->in_inode) {
-		WARN_ON_ONCE(!i->value_len);
-
-		ea_inode = ext4_xattr_inode_lookup_create(handle, inode,
-					i->value, i->value_len);
-		if (IS_ERR(ea_inode))
-			return PTR_ERR(ea_inode);
-	}
-	error = ext4_xattr_set_entry(i, s, handle, inode, ea_inode,
-				     false /* is_block */);
-	if (error) {
-		if (ea_inode) {
-			int error2;
-
-			error2 = ext4_xattr_inode_dec_ref(handle, ea_inode);
-			if (error2)
-				ext4_warning_inode(ea_inode, "dec ref error=%d",
-						   error2);
-
-			ext4_xattr_inode_free_quota(inode, ea_inode,
-						    i_size_read(ea_inode));
-			iput(ea_inode);
-		}
+	error = ext4_xattr_set_entry(i, s, handle, inode, false /* is_block */);
+	if (error)
 		return error;
-	}
 	header = IHDR(inode, ext4_raw_inode(&is->iloc));
 	if (!IS_LAST_ENTRY(s->first)) {
 		header->h_magic = cpu_to_le32(EXT4_XATTR_MAGIC);
@@ -2296,7 +2304,6 @@ int ext4_xattr_ibody_set(handle_t *handle, struct inode *inode,
 		header->h_magic = cpu_to_le32(0);
 		ext4_clear_inode_state(inode, EXT4_STATE_XATTR);
 	}
-	iput(ea_inode);
 	return 0;
 }
 
-- 
2.47.0