[f2fs-dev][PATCH 0/6 v2] f2fs: support inline dir

From: Chao Yu
Date: Wed Sep 24 2014 - 06:15:26 EST

There are large space in f2fs inode, so last inline data patch set have made
f2fs to acquire the ability of storing data of small file (less than ~3.4k)
directly in inode block, but not support inline dir. In this patch, we make
f2fs to support inline dir.

Inline dir layout is the same as inline data layout,
a. i_addr[0] are reserved space for converting from inline dir to regular one
when out-of-space occur in inline dentry.
b. i_addr[1..872] will be used as storing space of inline dentry.
c. i_addr[873..922] are reserved for inline xattr.

Since our max size of inline dir space is limit to MAX_INLINE_DATA (3488 bytes),
we introduce inline dentry struct fit for available space, then our dentry slot
number in inline dentry reduce to 182, less than normal dentry block's 214.

In inline dir mode, our dir entries will be lookuped/stored/deleted in the
inline dentry space of inode, util there are no more space to store new added
dir entry, in this case we will convert inline dentry to normal 0-index dentry
block and disable inline dir mode for this inode.

Benefit points:
a) space saving
1) Test with fsstress with special arguments, it can save about 7% space.
time fsstress -c -p 20 -n 500 -l 10 -d /mnt/f2fs -w -f chown=0 -f creat=10
-f dwrite=0 -f fdatasync=0 -f fsync=0 -f link=10 -f mkdir=10 -f mknod=10
-f rename=0 -f rmdir=0 -f symlink=10 -f truncate=0 -f unlink=0 -f write=10 -S
Dev 1K-blocks Used Available Use% Mounted on
empty /dev/sdb 20969472 1134600 19691512 6% /mnt/f2fs
based /dev/sdb 20969472 2331676 18494436 12% /mnt/f2fs
patched /dev/sdb 20969472 2247480 18578632 11% /mnt/f2fs
2) Test with storing kernel src, it can save less than 1.4% space.
empty /dev/sdb 20969472 1134600 19691512 6% /mnt/f2fs
based /dev/sdb 20969472 1934656 18891456 10% /mnt/f2fs
patched /dev/sdb 20969472 1923400 18902712 10% /mnt/f2fs

b) performance
Test with fsstress shows cost time reduce about 5%.
time fsstress -d /mnt/f2fs -l 5 -n 1000 -p 20 -c -r
based 135.652 s
patched 129.256 s (mount -o inline_dentry)

o introduce f2fs_drop_nlink from f2fs_delete_entry to reuse code in
o remove kmap/kunmap for inode page pointed out by Jaegeuk Kim.
o introduce a new mount option inline_dentry for inline dir pointed out by
Jaegeuk Kim.
o rebase to last dev of f2fs (20140924).
o retest performance/space-gain for inline dir excluding influence of inline

Chao Yu (6):
f2fs: add infra struct and helper for inline dir
f2fs: add a new mount option for inline dir
f2fs: export dir operations for inline dir
f2fs: add key function to handle inline dir
f2fs: enable inline dir handling
f2fs: update f2fs documentation for inline dir support

Documentation/filesystems/f2fs.txt | 4 +
fs/f2fs/dir.c | 103 +++++++----
fs/f2fs/f2fs.h | 40 ++++-
fs/f2fs/file.c | 2 +-
fs/f2fs/inline.c | 347 +++++++++++++++++++++++++++++++++++++
fs/f2fs/namei.c | 38 ++--
fs/f2fs/recovery.c | 5 +-
fs/f2fs/super.c | 7 +
include/linux/f2fs_fs.h | 19 ++
9 files changed, 512 insertions(+), 53 deletions(-)


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