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048832a3f4
Refactors shmem_pwrite() to replace the ->write_begin/end logic with a write_iter-based implementation using kiocb and iov_iter. While kernel_write() was considered, it caused about 50% performance regression. vfs_write() is not exported for kernel use. Therefore, file->f_op->write_iter() is called directly with a synchronously initialized kiocb to preserve performance and remove write_begin usage. Performance results use gem_pwrite on Intel CPU i7-10700 (average of 10 runs): - ./gem_pwrite --run-subtest bench -s 16384 Before: 0.205s, After: 0.214s - ./gem_pwrite --run-subtest bench -s 524288 Before: 6.1021s, After: 4.8047s Part of a series refactoring address_space_operations write_begin and write_end callbacks to use struct kiocb for passing write context and flags. Signed-off-by: Taotao Chen <chentaotao@didiglobal.com> Link: https://lore.kernel.org/20250716093559.217344-3-chentaotao@didiglobal.com Signed-off-by: Christian Brauner <brauner@kernel.org>