On Thu 24-01-13 13:49:45, Dmitry Monakhov wrote: > On Fri, 18 Jan 2013 13:00:38 +0100, Jan Kara <jack@xxxxxxx> wrote: > > Merging of uninitialized extents creates all sorts of interesting race > > possibilities when writeback / DIO races with fallocate. Thus > > ext4_convert_unwritten_extents_endio() has to deal with a case where > > extent to be converted needs to be split out first. That isn't nice > > for two reasons: > > > > 1) It may need allocation of extent tree block so ENOSPC is possible. > > 2) It complicates end_io handling code > As we already discussed your idea is 100% correct, but even with > what patch I still able to trigger situation where split it required. > I've got following error with this patch applied on top of 7f5118629f7 > EXT4-fs error (device dm-3): ext4_convert_unwritten_extents_endio:3411: > inode #12: comm kworker/u:4: Written extent modified before IO finished: > extent logical block 1379787, len 64; IO logical block 1379787, len 21 Drat, thanks for heads up. I did run xfstests on the patch set but apparently you are doing something more evil :) If I get your test & error right, you do AIO DIO to a file while doing truncate 0, fallocate SIZE, in a loop. And extent is found longer when we finish the IO. Am I right? Honza > ------------[ cut here ]------------ > WARNING: at fs/ext4/extents.c:4518 > ext4_convert_unwritten_extents+0x149/0x210 [ext4]() > Hardware name: > Modules linked in: ext4 jbd2 cpufreq_ondemand acpi_cpufreq freq_table > mperf coretemp kvm_intel kvm crc32c_intel microcode sg button ext3 jbd > mbcache sd_mod crc_t10dif ahci libahci pata_acpi ata_generic dm_mirror > dm_region_hash dm_log dm_mod > Pid: 249, comm: kworker/u:4 Not tainted 3.8.0-rc3+ #16 > Call Trace: > [<ffffffff8106fc23>] warn_slowpath_common+0xc3/0xf0 > [<ffffffff8106fc6a>] warn_slowpath_null+0x1a/0x20 > [<ffffffffa03fb909>] ext4_convert_unwritten_extents+0x149/0x210 [ext4] > [<ffffffff811064fa>] ? __lock_release+0x1da/0x1f0 > [<ffffffffa03c368e>] ext4_end_io+0x3e/0x160 [ext4] > [<ffffffff813aab40>] ? __list_del_entry+0x210/0x250 > [<ffffffffa03c3a21>] ext4_do_flush_completed_IO+0x101/0x280 [ext4] > [<ffffffffa03c3bb6>] ext4_end_io_work+0x16/0x20 [ext4] > [<ffffffff8109f7dd>] process_one_work+0x4ad/0x780 > [<ffffffff8109f6d2>] ? process_one_work+0x3a2/0x780 > [<ffffffffa03c3ba0>] ? ext4_do_flush_completed_IO+0x280/0x280 [ext4] > [<ffffffff810a3ed1>] worker_thread+0x3f1/0x590 > [<ffffffff810a3ae0>] ? manage_workers+0x210/0x210 > [<ffffffff810ac870>] kthread+0x100/0x110 > [<ffffffff810ac770>] ? __init_kthread_worker+0x70/0x70 > [<ffffffff81812e2c>] ret_from_fork+0x7c/0xb0 > [<ffffffff810ac770>] ? __init_kthread_worker+0x70/0x70 > ---[ end trace add5cefed72186f8 ]--- > EXT4-fs (dm-3): ext4_convert_unwritten_extents:4522: inode #12: block > 1379787: len 21: ext4_ext_map_blocks returned -5 > EXT4-fs (dm-3): failed to convert unwritten extents to written > extents -- potential data loss! (inode 12, offset 5651562496, size > 131072, error -5) > > I've run 286'th xfstest (this is my own copy of xfstest so 286'th test > is differ from mainstream one) you can find it here > https://raw.github.com/dmonakhov/xfstests/devel/286 > In two words it is stress test which run DIO/AIO,truncate,fallocate in parallel. > Also you need recent FIO(http://git.kernel.dk/?p=fio.git;a=summary) > > Currently I try to understand what caused this issue. > > > > So we disable merging of uninitialized extents which allows us to simplify > > the code. Extents will get merged after they are converted to initialized > > ones. > > > > Reviewed-by: Zheng Liu <wenqing.lz@xxxxxxxxxx> > > Signed-off-by: Jan Kara <jack@xxxxxxx> > > --- > > fs/ext4/extents.c | 61 +++++++++++++++------------------------------------- > > 1 files changed, 18 insertions(+), 43 deletions(-) > > > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > > index 26af228..f1ce33a 100644 > > --- a/fs/ext4/extents.c > > +++ b/fs/ext4/extents.c > > @@ -54,9 +54,6 @@ > > #define EXT4_EXT_MARK_UNINIT1 0x2 /* mark first half uninitialized */ > > #define EXT4_EXT_MARK_UNINIT2 0x4 /* mark second half uninitialized */ > > > > -#define EXT4_EXT_DATA_VALID1 0x8 /* first half contains valid data */ > > -#define EXT4_EXT_DATA_VALID2 0x10 /* second half contains valid data */ > > - > > static __le32 ext4_extent_block_csum(struct inode *inode, > > struct ext4_extent_header *eh) > > { > > @@ -1579,20 +1576,17 @@ int > > ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1, > > struct ext4_extent *ex2) > > { > > - unsigned short ext1_ee_len, ext2_ee_len, max_len; > > + unsigned ext1_ee_len, ext2_ee_len; > > > > /* > > - * Make sure that either both extents are uninitialized, or > > - * both are _not_. > > + * Make sure that both extents are initialized. We don't merge > > + * uninitialized extents so that we can be sure that end_io code has > > + * the extent that was written properly split out and conversion to > > + * initialized is trivial. > > */ > > - if (ext4_ext_is_uninitialized(ex1) ^ ext4_ext_is_uninitialized(ex2)) > > + if (ext4_ext_is_uninitialized(ex1) || ext4_ext_is_uninitialized(ex2)) > > return 0; > > > > - if (ext4_ext_is_uninitialized(ex1)) > > - max_len = EXT_UNINIT_MAX_LEN; > > - else > > - max_len = EXT_INIT_MAX_LEN; > > - > > ext1_ee_len = ext4_ext_get_actual_len(ex1); > > ext2_ee_len = ext4_ext_get_actual_len(ex2); > > > > @@ -1605,7 +1599,7 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1, > > * as an RO_COMPAT feature, refuse to merge to extents if > > * this can result in the top bit of ee_len being set. > > */ > > - if (ext1_ee_len + ext2_ee_len > max_len) > > + if (ext1_ee_len + ext2_ee_len > EXT_INIT_MAX_LEN) > > return 0; > > #ifdef AGGRESSIVE_TEST > > if (ext1_ee_len >= 4) > > @@ -2959,9 +2953,6 @@ static int ext4_split_extent_at(handle_t *handle, > > unsigned int ee_len, depth; > > int err = 0; > > > > - BUG_ON((split_flag & (EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2)) == > > - (EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2)); > > - > > ext_debug("ext4_split_extents_at: inode %lu, logical" > > "block %llu\n", inode->i_ino, (unsigned long long)split); > > > > @@ -3020,14 +3011,7 @@ static int ext4_split_extent_at(handle_t *handle, > > > > err = ext4_ext_insert_extent(handle, inode, path, &newex, flags); > > if (err == -ENOSPC && (EXT4_EXT_MAY_ZEROOUT & split_flag)) { > > - if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) { > > - if (split_flag & EXT4_EXT_DATA_VALID1) > > - err = ext4_ext_zeroout(inode, ex2); > > - else > > - err = ext4_ext_zeroout(inode, ex); > > - } else > > - err = ext4_ext_zeroout(inode, &orig_ex); > > - > > + err = ext4_ext_zeroout(inode, &orig_ex); > > if (err) > > goto fix_extent_len; > > /* update the extent length and mark as initialized */ > > @@ -3085,8 +3069,6 @@ static int ext4_split_extent(handle_t *handle, > > if (uninitialized) > > split_flag1 |= EXT4_EXT_MARK_UNINIT1 | > > EXT4_EXT_MARK_UNINIT2; > > - if (split_flag & EXT4_EXT_DATA_VALID2) > > - split_flag1 |= EXT4_EXT_DATA_VALID1; > > err = ext4_split_extent_at(handle, inode, path, > > map->m_lblk + map->m_len, split_flag1, flags1); > > if (err) > > @@ -3099,8 +3081,7 @@ static int ext4_split_extent(handle_t *handle, > > return PTR_ERR(path); > > > > if (map->m_lblk >= ee_block) { > > - split_flag1 = split_flag & (EXT4_EXT_MAY_ZEROOUT | > > - EXT4_EXT_DATA_VALID2); > > + split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT; > > if (uninitialized) > > split_flag1 |= EXT4_EXT_MARK_UNINIT1; > > if (split_flag & EXT4_EXT_MARK_UNINIT2) > > @@ -3379,8 +3360,7 @@ static int ext4_split_unwritten_extents(handle_t *handle, > > > > split_flag |= ee_block + ee_len <= eof_block ? EXT4_EXT_MAY_ZEROOUT : 0; > > split_flag |= EXT4_EXT_MARK_UNINIT2; > > - if (flags & EXT4_GET_BLOCKS_CONVERT) > > - split_flag |= EXT4_EXT_DATA_VALID2; > > + > > flags |= EXT4_GET_BLOCKS_PRE_IO; > > return ext4_split_extent(handle, inode, path, map, split_flag, flags); > > } > > @@ -3405,20 +3385,15 @@ static int ext4_convert_unwritten_extents_endio(handle_t *handle, > > "block %llu, max_blocks %u\n", inode->i_ino, > > (unsigned long long)ee_block, ee_len); > > > > - /* If extent is larger than requested then split is required */ > > + /* Extent is larger than requested? */ > > if (ee_block != map->m_lblk || ee_len > map->m_len) { > > - err = ext4_split_unwritten_extents(handle, inode, map, path, > > - EXT4_GET_BLOCKS_CONVERT); > > - if (err < 0) > > - goto out; > > - ext4_ext_drop_refs(path); > > - path = ext4_ext_find_extent(inode, map->m_lblk, path); > > - if (IS_ERR(path)) { > > - err = PTR_ERR(path); > > - goto out; > > - } > > - depth = ext_depth(inode); > > - ex = path[depth].p_ext; > > + EXT4_ERROR_INODE(inode, "Written extent modified before IO" > > + " finished: extent logical block %llu, len %u; IO" > > + " logical block %llu, len %u\n", > > + (unsigned long long)ee_block, ee_len, > > + (unsigned long long)map->m_lblk, map->m_len); > > + err = -EIO; > > + goto out; > > } > > > > err = ext4_ext_get_access(handle, inode, path + depth); > > -- > > 1.7.1 > > > > -- > > 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 -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- 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
