ext2: Handle fiemap on empty files to prevent EINVAL

Previously, ext2_fiemap would unconditionally apply "len = min_t(u64, len,
i_size_read(inode));", When inode->i_size was 0 (for an empty file), this
would reduce the requested len to 0. Passing len = 0 to iomap_fiemap could
then result in an -EINVAL error, even for valid queries on empty files.

Link: https://github.com/linux-test-project/ltp/issues/1246
Signed-off-by: Wei Gao <wegao@suse.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250613152402.3432135-1-wegao@suse.com

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 30f8201c155f408fe6a971d7a20ff3b0d3e853a9..177b1f852b63ac9811d78577451a7fae87f7664c 100644 (file)
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -895,9 +895,19 @@ int ext2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                u64 start, u64 len)
 {
        int ret;
+       loff_t i_size;
 
        inode_lock(inode);
-       len = min_t(u64, len, i_size_read(inode));
+       i_size = i_size_read(inode);
+       /*
+        * iomap_fiemap() returns EINVAL for 0 length. Make sure we don't trim
+        * length to 0 but still trim the range as much as possible since
+        * ext2_get_blocks() iterates unmapped space block by block which is
+        * slow.
+        */
+       if (i_size == 0)
+               i_size = 1;
+       len = min_t(u64, len, i_size);
        ret = iomap_fiemap(inode, fieinfo, start, len, &ext2_iomap_ops);
        inode_unlock(inode);