linux.git/fs/f2fs/segment.c, branch v3.11

f2fs: remove reusing any prefree segments

2013-07-01T23:48:15+00:00

This patch removes check_prefree_segments initially designed to enhance the
performance by narrowing the range of LBA usage across the whole block device.

When allocating a new segment, previous f2fs tries to find proper prefree
segments, and then, if finds a segment, it reuses the segment for further
data or node block allocation.

However, I found that this was totally wrong approach since the prefree segments
have several data or node blocks that will be used by the roll-forward mechanism
operated after sudden-power-off.

Let's assume the following scenario.

/* write 8MB with fsync */
for (i = 0; i < 2048; i++) {
	offset = i * 4096;
	write(fd, offset, 4KB);
	fsync(fd);
}

In this case, naive segment allocation sequence will be like:
 data segment: x, x+1, x+2, x+3
 node segment: y, y+1, y+2, y+3.

But, if we can reuse prefree segments, the sequence can be like:
 data segment: x, x+1, y, y+1
 node segment: y, y+1, y+2, y+3.
Because, y, y+1, and y+2 became prefree segments one by one, and those are
reused by data allocation.

After conducting this workload, we should consider how to recover the latest
inode with its data.
If we reuse the prefree segments such as y or y+1, we lost the old node blocks
so that f2fs even cannot start roll-forward recovery.

Therefore, I suggest that we should remove reusing prefree segments.

Signed-off-by: Jaegeuk Kim

f2fs: optimize the init_dirty_segmap function

2013-07-01T23:48:14+00:00

Optimize the while loop condition

Since this condition will always be true and while loop will
be terminated by the following condition in code:

if (segno >= TOTAL_SEGS(sbi))
    break;
Hence we can replace the while loop condition with while(1)
instead of always checking for segno to be less than Total segs.

Also we do not need to use TOTAL_SEGS() everytime. We can store
this value in a local variable since this value is constant.

Signed-off-by: Namjae Jeon 
Signed-off-by: Pankaj Kumar 
Signed-off-by: Jaegeuk Kim

f2fs: recover wrong pino after checkpoint during fsync

2013-06-14T00:04:45+00:00

If a file is linked, f2fs loose its parent inode number so that fsync calls
for the linked file should do checkpoint all the time.
But, if we can recover its parent inode number after the checkpoint, we can
adjust roll-forward mechanism for the further fsync calls, which is able to
improve the fsync performance significatly.

Signed-off-by: Jaegeuk Kim

f2fs: make locate_dirty_segment() as static

2013-06-14T00:04:44+00:00

It's used only locally and could be static.

Signed-off-by: Haicheng Li 
Signed-off-by: Jaegeuk Kim

f2fs: remove unnecessary parameter "offset" from __add_sum_entry()

2013-06-14T00:04:43+00:00

We can get the value directly from pointer "curseg".

Signed-off-by: Haicheng Li 
Signed-off-by: Jaegeuk Kim

f2fs: push some variables to debug part

2013-05-28T06:03:05+00:00

Some, counters are needed only for the statistical information
while debugging.
So, those can be controlled using CONFIG_F2FS_STAT_FS,
pushing the usage for few variables under this flag.

Signed-off-by: Namjae Jeon 
Signed-off-by: Amit Sahrawat 
Signed-off-by: Jaegeuk Kim

f2fs: remove unecessary variable and code

2013-05-28T06:03:02+00:00

Code cleanup without behavior changed.

Signed-off-by: Haicheng Li 
Signed-off-by: Jaegeuk Kim

f2fs: modify the number of issued pages to merge IOs

2013-04-30T03:07:32+00:00

When testing f2fs on an SSD, I found some 128 page IOs followed by 1 page IO
were issued by f2fs_write_node_pages.
This means that there were some mishandling flows which degrades performance.

Previous f2fs_write_node_pages determines the number of pages to be written,
nr_to_write, as follows.

1. The bio_get_nr_vecs returns 129 pages.
2. The bio_alloc makes a room for 128 pages.
3. The initial 128 pages go into one bio.
4. The existing bio is submitted, and a new bio is prepared for the last 1 page.
5. Finally, sync_node_pages submits the last 1 page bio.

The problem is from the use of bio_get_nr_vecs, so this patch replace it
with max_hw_blocks using queue_max_sectors.

Signed-off-by: Jaegeuk Kim

f2fs: add REQ_META about metadata requests for submit

2013-04-26T01:35:11+00:00

Adding REQ_META for all the metadata requests can help in improving the
FS performance, if the underlying device supports TAGGING.
So, when considering the submit_bio path for all the f2fs requests. We can
add REQ_META for all the META requests.
As a precursor to this change we considered the commit
4265900e0be653f5b78baf2816857ef57cf1332f 'mmc: MMC-4.5 Data Tag Support'

Signed-off-by: Namjae Jeon 
Signed-off-by: Amit Sahrawat 
Signed-off-by: Jaegeuk Kim

f2fs: add tracepoints for write page operations

2013-04-23T09:15:17+00:00

Add tracepoints to debug the various page write operation
like data pages, meta pages.

Signed-off-by: Namjae Jeon 
Signed-off-by: Pankaj Kumar 
Acked-by: Steven Rostedt 
[Jaegeuk: remove unnecessary tracepoints]
Signed-off-by: Jaegeuk Kim