[RFC PATCH 3/9] ext4: use safe convert path for inline data write overflow

[Yun Zhou]

Replace ext4_convert_inline_data_to_extent() with
ext4_convert_inline_data() in the write paths that handle inline data
overflow.

ext4_convert_inline_data_to_extent() destroys inline data before
allocating the target block.  If block allocation fails (e.g. -ENOSPC),
the inline data is already gone and cannot be recovered -- a potential
data loss on crash.

ext4_convert_inline_data() keeps
a copy of the inline data in a buffer and restores it on failure, making
the conversion safe against allocation failures.

Signed-off-by: Yun Zhou <yun.zhou@xxxxxxxxxxxxx>
---
 fs/ext4/inline.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index ceee69a66482..8f1efe4297a0 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -724,7 +724,7 @@ int ext4_generic_write_inline_data(struct address_space *mapping,
 		if (!da) {
 			brelse(iloc.bh);
 			/* Retry inside */
-			return ext4_convert_inline_data_to_extent(mapping, inode);
+			return ext4_convert_inline_data(inode);
 		}
 
 		ret = ext4_da_convert_inline_data_to_extent(mapping, inode);
@@ -785,7 +785,7 @@ int ext4_try_to_write_inline_data(struct address_space *mapping,
 				  struct folio **foliop)
 {
 	if (pos + len > ext4_get_max_inline_size(inode))
-		return ext4_convert_inline_data_to_extent(mapping, inode);
+		return ext4_convert_inline_data(inode);
 	return ext4_generic_write_inline_data(mapping, inode, pos, len,
 					      foliop, false);
 }
-- 
2.43.0