Ext4: Fix delalloc enospace handling counter update race From: Mingming Cao <cmm@xxxxxxxxxx> Ext4 delalloc reserve meta blocks ahead of time so later when real block allocation fs will not short of free blocks for allocating meta blocks. It keeps track of the real number of new allocated meta data blocks, so after block allocation it will update how much meta data blocks still need to be reserved for that inode. Both per inode reserved metadata blocks and per-allocation allocated metablocks are protected by the per inode delalloc reservation lock. The per-allocation allocated metablocks counter should be protected by the i_data_sem as well, so that it could avoid race with other block allocation to the same inode in parallel. The patch moves the code under the i_data_sem protection. Also in the case of truncate, we should not clear the per-allocation allocated metablocks counter as that may be in-use by parallel allocation. The patch only clear the per-allocation allocated metablocks when allocation is successfully returned. Signed-off-by: Mingming Cao <cmm@xxxxxxxxxx> --- fs/ext4/inode.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) Index: linux-2.6.26-rc9/fs/ext4/inode.c =================================================================== --- linux-2.6.26-rc9.orig/fs/ext4/inode.c 2008-07-14 08:54:25.000000000 -0700 +++ linux-2.6.26-rc9/fs/ext4/inode.c 2008-07-14 09:23:29.000000000 -0700 @@ -1060,8 +1060,18 @@ int ext4_get_blocks_wrap(handle_t *handl ~EXT4_EXT_MIGRATE; } } - if (flag) + + if (flag) { EXT4_I(inode)->i_delalloc_reserved_flag = 0; + /* + * Update reserved blocks/metadata blocks + * after successful block allocation + * which were deferred till now + */ + if ((retval > 0) && buffer_delay(bh)) + ext4_da_release_space(inode, retval, 0); + } + up_write((&EXT4_I(inode)->i_data_sem)); return retval; } @@ -1519,7 +1529,8 @@ void ext4_da_release_space(struct inode BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks); EXT4_I(inode)->i_reserved_meta_blocks = mdb; - EXT4_I(inode)->i_allocated_meta_blocks = 0; + if (used) + EXT4_I(inode)->i_allocated_meta_blocks = 0; spin_unlock(&EXT4_I(inode)->i_block_reservation_lock); } @@ -2005,10 +2016,6 @@ static int ext4_da_get_block_write(struc if (ret > 0) { bh_result->b_size = (ret << inode->i_blkbits); - /* release reserved-but-unused meta blocks */ - if (buffer_delay(bh_result)) - ext4_da_release_space(inode, ret, 0); - /* * Update on-disk size along with block allocation * we don't use 'extend_disksize' as size may change -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html