From: Hyeong-Jun Kim hj514.kim@samsung.com
commit 7377e853967ba45bf409e3b5536624d2cbc99f21 upstream.
There is a potential deadlock between writeback process and a process performing write_begin() or write_cache_pages() while trying to write same compress file, but not compressable, as below:
[Process A] - doing checkpoint [Process B] [Process C] f2fs_write_cache_pages() - lock_page() [all pages in cluster, 0-31] - f2fs_write_multi_pages() - f2fs_write_raw_pages() - f2fs_write_single_data_page() - f2fs_do_write_data_page() - return -EAGAIN [f2fs_trylock_op() failed] - unlock_page(page) [e.g., page 0] - generic_perform_write() - f2fs_write_begin() - f2fs_prepare_compress_overwrite() - prepare_compress_overwrite() - lock_page() [e.g., page 0] - lock_page() [e.g., page 1] - lock_page(page) [e.g., page 0]
Since there is no compress process, it is no longer necessary to hold locks on every pages in cluster within f2fs_write_raw_pages().
This patch changes f2fs_write_raw_pages() to release all locks first and then perform write same as the non-compress file in f2fs_write_cache_pages().
Fixes: 4c8ff7095bef ("f2fs: support data compression") Signed-off-by: Hyeong-Jun Kim hj514.kim@samsung.com Signed-off-by: Sungjong Seo sj1557.seo@samsung.com Signed-off-by: Youngjin Gil youngjin.gil@samsung.com Reviewed-by: Chao Yu chao@kernel.org Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/f2fs/compress.c | 50 ++++++++++++++++++++++---------------------------- 1 file changed, 22 insertions(+), 28 deletions(-)
--- a/fs/f2fs/compress.c +++ b/fs/f2fs/compress.c @@ -1468,25 +1468,38 @@ static int f2fs_write_raw_pages(struct c enum iostat_type io_type) { struct address_space *mapping = cc->inode->i_mapping; - int _submitted, compr_blocks, ret; - int i = -1, err = 0; + int _submitted, compr_blocks, ret, i;
compr_blocks = f2fs_compressed_blocks(cc); - if (compr_blocks < 0) { - err = compr_blocks; - goto out_err; + + for (i = 0; i < cc->cluster_size; i++) { + if (!cc->rpages[i]) + continue; + + redirty_page_for_writepage(wbc, cc->rpages[i]); + unlock_page(cc->rpages[i]); }
+ if (compr_blocks < 0) + return compr_blocks; + for (i = 0; i < cc->cluster_size; i++) { if (!cc->rpages[i]) continue; retry_write: + lock_page(cc->rpages[i]); + if (cc->rpages[i]->mapping != mapping) { +continue_unlock: unlock_page(cc->rpages[i]); continue; }
- BUG_ON(!PageLocked(cc->rpages[i])); + if (!PageDirty(cc->rpages[i])) + goto continue_unlock; + + if (!clear_page_dirty_for_io(cc->rpages[i])) + goto continue_unlock;
ret = f2fs_write_single_data_page(cc->rpages[i], &_submitted, NULL, NULL, wbc, io_type, @@ -1501,26 +1514,15 @@ retry_write: * avoid deadlock caused by cluster update race * from foreground operation. */ - if (IS_NOQUOTA(cc->inode)) { - err = 0; - goto out_err; - } + if (IS_NOQUOTA(cc->inode)) + return 0; ret = 0; cond_resched(); congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT); - lock_page(cc->rpages[i]); - - if (!PageDirty(cc->rpages[i])) { - unlock_page(cc->rpages[i]); - continue; - } - - clear_page_dirty_for_io(cc->rpages[i]); goto retry_write; } - err = ret; - goto out_err; + return ret; }
*submitted += _submitted; @@ -1529,14 +1531,6 @@ retry_write: f2fs_balance_fs(F2FS_M_SB(mapping), true);
return 0; -out_err: - for (++i; i < cc->cluster_size; i++) { - if (!cc->rpages[i]) - continue; - redirty_page_for_writepage(wbc, cc->rpages[i]); - unlock_page(cc->rpages[i]); - } - return err; }
int f2fs_write_multi_pages(struct compress_ctx *cc,