From df981d03eeff7971ac7e6ff37000bfa702327ef1 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Fri, 17 Aug 2012 09:48:17 -0400 Subject: ext4: add max_dir_size_kb mount option Very large directories can cause significant performance problems, or perhaps even invoke the OOM killer, if the process is running in a highly constrained memory environment (whether it is VM's with a small amount of memory or in a small memory cgroup). So it is useful, in cloud server/data center environments, to be able to set a filesystem-wide cap on the maximum size of a directory, to ensure that directories never get larger than a sane size. We do this via a new mount option, max_dir_size_kb. If there is an attempt to grow the directory larger than max_dir_size_kb, the system call will return ENOSPC instead. Google-Bug-Id: 6863013 Signed-off-by: "Theodore Ts'o" --- Documentation/filesystems/ext4.txt | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'Documentation') diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index 1b7f9acbcbbe..104322bf378c 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -375,6 +375,16 @@ dioread_nolock locking. If the dioread_nolock option is specified Because of the restrictions this options comprises it is off by default (e.g. dioread_lock). +max_dir_size_kb=n This limits the size of directories so that any + attempt to expand them beyond the specified + limit in kilobytes will cause an ENOSPC error. + This is useful in memory constrained + environments, where a very large directory can + cause severe performance problems or even + provoke the Out Of Memory killer. (For example, + if there is only 512mb memory available, a 176mb + directory may seriously cramp the system's style.) + i_version Enable 64-bit inode version support. This option is off by default. -- cgit v1.2.3-59-g8ed1b From 67a5da564f97f31c4054d358e00b34d7ee570da5 Mon Sep 17 00:00:00 2001 From: Zheng Liu Date: Fri, 17 Aug 2012 09:54:17 -0400 Subject: ext4: make the zero-out chunk size tunable Currently in ext4 the length of zero-out chunk is set to 7 file system blocks. But if an inode has uninitailized extents from using fallocate to preallocate space, and the workload issues many random writes, this can cause a fragmented extent tree that will unnecessarily grow the extent tree. So create a new sysfs tunable, extent_max_zeroout_kb, which controls the maximum size where blocks will be zeroed out instead of creating a new uninitialized extent. The default of this has been sent to 32kb. CC: Zach Brown CC: Andreas Dilger Signed-off-by: Zheng Liu Signed-off-by: "Theodore Ts'o" --- Documentation/ABI/testing/sysfs-fs-ext4 | 13 +++++++++++++ fs/ext4/ext4.h | 3 +++ fs/ext4/extents.c | 25 +++++++++++++------------ fs/ext4/super.c | 3 +++ 4 files changed, 32 insertions(+), 12 deletions(-) (limited to 'Documentation') diff --git a/Documentation/ABI/testing/sysfs-fs-ext4 b/Documentation/ABI/testing/sysfs-fs-ext4 index f22ac0872ae8..c631253cf85c 100644 --- a/Documentation/ABI/testing/sysfs-fs-ext4 +++ b/Documentation/ABI/testing/sysfs-fs-ext4 @@ -96,3 +96,16 @@ Contact: "Theodore Ts'o" Description: The maximum number of megabytes the writeback code will try to write out before move on to another inode. + +What: /sys/fs/ext4//extent_max_zeroout_kb +Date: August 2012 +Contact: "Theodore Ts'o" +Description: + The maximum number of kilobytes which will be zeroed + out in preference to creating a new uninitialized + extent when manipulating an inode's extent tree. Note + that using a larger value will increase the + variability of time necessary to complete a random + write operation (since a 4k random write might turn + into a much larger write due to the zeroout + operation). diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 7c0841ecde6c..0df5ee102b61 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1271,6 +1271,9 @@ struct ext4_sb_info { unsigned long s_sectors_written_start; u64 s_kbytes_written; + /* the size of zero-out chunk */ + unsigned int s_extent_max_zeroout_kb; + unsigned int s_log_groups_per_flex; struct flex_groups *s_flex_groups; diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index e8755c21f4b9..2f082abf4992 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3085,7 +3085,6 @@ out: return err ? err : map->m_len; } -#define EXT4_EXT_ZERO_LEN 7 /* * This function is called by ext4_ext_map_blocks() if someone tries to write * to an uninitialized extent. It may result in splitting the uninitialized @@ -3111,13 +3110,14 @@ static int ext4_ext_convert_to_initialized(handle_t *handle, struct ext4_map_blocks *map, struct ext4_ext_path *path) { + struct ext4_sb_info *sbi; struct ext4_extent_header *eh; struct ext4_map_blocks split_map; struct ext4_extent zero_ex; struct ext4_extent *ex; ext4_lblk_t ee_block, eof_block; unsigned int ee_len, depth; - int allocated; + int allocated, max_zeroout = 0; int err = 0; int split_flag = 0; @@ -3125,6 +3125,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle, "block %llu, max_blocks %u\n", inode->i_ino, (unsigned long long)map->m_lblk, map->m_len); + sbi = EXT4_SB(inode->i_sb); eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >> inode->i_sb->s_blocksize_bits; if (eof_block < map->m_lblk + map->m_len) @@ -3224,9 +3225,12 @@ static int ext4_ext_convert_to_initialized(handle_t *handle, */ split_flag |= ee_block + ee_len <= eof_block ? EXT4_EXT_MAY_ZEROOUT : 0; - /* If extent has less than 2*EXT4_EXT_ZERO_LEN zerout directly */ - if (ee_len <= 2*EXT4_EXT_ZERO_LEN && - (EXT4_EXT_MAY_ZEROOUT & split_flag)) { + if (EXT4_EXT_MAY_ZEROOUT & split_flag) + max_zeroout = sbi->s_extent_max_zeroout_kb >> + inode->i_sb->s_blocksize_bits; + + /* If extent is less than s_max_zeroout_kb, zeroout directly */ + if (max_zeroout && (ee_len <= max_zeroout)) { err = ext4_ext_zeroout(inode, ex); if (err) goto out; @@ -3250,9 +3254,8 @@ static int ext4_ext_convert_to_initialized(handle_t *handle, split_map.m_lblk = map->m_lblk; split_map.m_len = map->m_len; - if (allocated > map->m_len) { - if (allocated <= EXT4_EXT_ZERO_LEN && - (EXT4_EXT_MAY_ZEROOUT & split_flag)) { + if (max_zeroout && (allocated > map->m_len)) { + if (allocated <= max_zeroout) { /* case 3 */ zero_ex.ee_block = cpu_to_le32(map->m_lblk); @@ -3264,9 +3267,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle, goto out; split_map.m_lblk = map->m_lblk; split_map.m_len = allocated; - } else if ((map->m_lblk - ee_block + map->m_len < - EXT4_EXT_ZERO_LEN) && - (EXT4_EXT_MAY_ZEROOUT & split_flag)) { + } else if (map->m_lblk - ee_block + map->m_len < max_zeroout) { /* case 2 */ if (map->m_lblk != ee_block) { zero_ex.ee_block = ex->ee_block; @@ -3286,7 +3287,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle, } allocated = ext4_split_extent(handle, inode, path, - &split_map, split_flag, 0); + &split_map, split_flag, 0); if (allocated < 0) err = allocated; diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 5a97e590692d..0423e2e7f615 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2541,6 +2541,7 @@ EXT4_RW_ATTR_SBI_UI(mb_order2_req, s_mb_order2_reqs); EXT4_RW_ATTR_SBI_UI(mb_stream_req, s_mb_stream_request); EXT4_RW_ATTR_SBI_UI(mb_group_prealloc, s_mb_group_prealloc); EXT4_RW_ATTR_SBI_UI(max_writeback_mb_bump, s_max_writeback_mb_bump); +EXT4_RW_ATTR_SBI_UI(extent_max_zeroout_kb, s_extent_max_zeroout_kb); EXT4_ATTR(trigger_fs_error, 0200, NULL, trigger_test_error); static struct attribute *ext4_attrs[] = { @@ -2556,6 +2557,7 @@ static struct attribute *ext4_attrs[] = { ATTR_LIST(mb_stream_req), ATTR_LIST(mb_group_prealloc), ATTR_LIST(max_writeback_mb_bump), + ATTR_LIST(extent_max_zeroout_kb), ATTR_LIST(trigger_fs_error), NULL, }; @@ -3756,6 +3758,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) sbi->s_stripe = ext4_get_stripe_size(sbi); sbi->s_max_writeback_mb_bump = 128; + sbi->s_extent_max_zeroout_kb = 32; /* * set up enough so that it can read an inode -- cgit v1.2.3-59-g8ed1b