linux-stable.git/fs/f2fs/segment.c, branch v3.12

f2fs: fix a compound statement label error

2013-08-19T02:51:08+00:00

An error "label at end of compound statement" will occur if CONFIG_F2FS_STAT_FS
disabled.
fs/f2fs/segment.c:556:1: error: label at end of compound statement
So clean up the 'out' label to fix it.

Reported-by: Fengguang Wu 
Signed-off-by: Gu Zheng 
Signed-off-by: Jaegeuk Kim

f2fs: clean up the needless end 'return' of void function

2013-08-12T02:49:22+00:00

Signed-off-by: Gu Zheng 
Signed-off-by: Jaegeuk Kim

f2fs: fix a deadlock in fsync

2013-08-06T13:00:36+00:00

This patch fixes a deadlock bug that occurs quite often when there are
concurrent write and fsync on a same file.

Following is the simplified call trace when tasks get hung.

fsync thread:
- f2fs_sync_file
 ...
 - f2fs_write_data_pages
 ...
  - update_extent_cache
  ...
   - update_inode
    - wait_on_page_writeback

bdi writeback thread
- __writeback_single_inode
 - f2fs_write_data_pages
  - mutex_lock(sbi->writepages)

The deadlock happens when the fsync thread waits on a inode page that has
been added to the f2fs' cached bio sbi->bio[NODE], and unfortunately,
no one else could be able to submit the cached bio to block layer for
writeback. This is because the fsync thread already hold a sbi->fs_lock and
the sbi->writepages lock, causing the bdi thread being blocked when attempt
to write data pages for the same inode. At the same time, f2fs_gc thread
does not notice the situation and could not help. Even the sync syscall
gets blocked.

To fix it, we could submit the cached bio first before waiting on a inode page
that is being written back.

Signed-off-by: Jin Xu 
[Jaegeuk Kim: add more cases to use f2fs_wait_on_page_writeback]
Signed-off-by: Jaegeuk Kim

f2fs: move bio_private allocation out of f2fs_bio_alloc()

2013-07-30T06:17:03+00:00

bio->bi_private is not always needed. As in the reading data path,
end_read_io does not need bio_private for further using, so moving
bio_private allocation out of f2fs_bio_alloc(). Alloc it in the
submit_write_page(), and ignore it in the f2fs_readpage().

Signed-off-by: Gu Zheng 
Signed-off-by: Jaegeuk Kim

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