From: yangerkun <yangerkun@xxxxxxxxxx> commit 1811bc401aa58c7bdb0df3205aa6613b49d32127 upstream. After we drop i_data sem, we need to reload the ext4_ext_path structure since the extent tree can change once i_data_sem is released. This addresses the BUG: [52117.465187] ------------[ cut here ]------------ [52117.465686] kernel BUG at fs/ext4/extents.c:1756! ... [52117.478306] Call Trace: [52117.478565] ext4_ext_shift_extents+0x3ee/0x710 [52117.479020] ext4_fallocate+0x139c/0x1b40 [52117.479405] ? __do_sys_newfstat+0x6b/0x80 [52117.479805] vfs_fallocate+0x151/0x4b0 [52117.480177] ksys_fallocate+0x4a/0xa0 [52117.480533] __x64_sys_fallocate+0x22/0x30 [52117.480930] do_syscall_64+0x35/0x80 [52117.481277] entry_SYSCALL_64_after_hwframe+0x44/0xae [52117.481769] RIP: 0033:0x7fa062f855ca Cc: stable@xxxxxxxxxx Link: https://lore.kernel.org/r/20210903062748.4118886-4-yangerkun@xxxxxxxxxx Signed-off-by: yangerkun <yangerkun@xxxxxxxxxx> Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ext4/extents.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -5012,8 +5012,11 @@ ext4_ext_shift_path_extents(struct ext4_ restart_credits = ext4_writepage_trans_blocks(inode); err = ext4_datasem_ensure_credits(handle, inode, credits, restart_credits, 0); - if (err) + if (err) { + if (err > 0) + err = -EAGAIN; goto out; + } err = ext4_ext_get_access(handle, inode, path + depth); if (err) @@ -5087,6 +5090,7 @@ ext4_ext_shift_extents(struct inode *ino int ret = 0, depth; struct ext4_extent *extent; ext4_lblk_t stop, *iterator, ex_start, ex_end; + ext4_lblk_t tmp = EXT_MAX_BLOCKS; /* Let path point to the last extent */ path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL, @@ -5140,11 +5144,15 @@ ext4_ext_shift_extents(struct inode *ino * till we reach stop. In case of right shift, iterator points to stop * and it is decreased till we reach start. */ +again: if (SHIFT == SHIFT_LEFT) iterator = &start; else iterator = &stop; + if (tmp != EXT_MAX_BLOCKS) + *iterator = tmp; + /* * Its safe to start updating extents. Start and stop are unsigned, so * in case of right shift if extent with 0 block is reached, iterator @@ -5173,6 +5181,7 @@ ext4_ext_shift_extents(struct inode *ino } } + tmp = *iterator; if (SHIFT == SHIFT_LEFT) { extent = EXT_LAST_EXTENT(path[depth].p_hdr); *iterator = le32_to_cpu(extent->ee_block) + @@ -5191,6 +5200,9 @@ ext4_ext_shift_extents(struct inode *ino } ret = ext4_ext_shift_path_extents(path, shift, inode, handle, SHIFT); + /* iterator can be NULL which means we should break */ + if (ret == -EAGAIN) + goto again; if (ret) break; }
