Messages in this thread | | | Date | Tue, 7 Nov 2023 22:39:35 +0800 | From | Chao Yu <> | Subject | Re: [PATCH 1/1] f2fs: fix fallocate failed under pinned block situation |
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On 2023/10/30 17:40, Wu Bo wrote: > If GC victim has pinned block, it can't be recycled. > And if GC is foreground running, after many failure try, the pinned file > is expected to be clear pin flag. To enable the section be recycled. > > But when fallocate trigger FG_GC, GC can never recycle the pinned > section. Because GC will go to stop before the failure try meet the threshold: > if (has_enough_free_secs(sbi, sec_freed, 0)) { > if (!gc_control->no_bg_gc && > total_sec_freed < gc_control->nr_free_secs) > goto go_gc_more; > goto stop; > } > > So when fallocate trigger FG_GC, at least recycle one.
Hmm... it may break pinfile's semantics at least on one pinned file? In this case, I prefer to fail fallocate() rather than unpinning file, in order to avoid leaving invalid LBA references of unpinned file held by userspace.
Thoughts?
Thanks,
> > This issue can be reproduced by filling f2fs space as following layout. > Every segment has one block is pinned: > +-+-+-+-+-+-+-----+-+ > | | |p| | | | ... | | seg_n > +-+-+-+-+-+-+-----+-+ > +-+-+-+-+-+-+-----+-+ > | | |p| | | | ... | | seg_n+1 > +-+-+-+-+-+-+-----+-+ > ... > +-+-+-+-+-+-+-----+-+ > | | |p| | | | ... | | seg_n+k > +-+-+-+-+-+-+-----+-+ > > And following are steps to reproduce this issue: > dd if=/dev/zero of=./f2fs_pin.img bs=2M count=1024 > mkfs.f2fs f2fs_pin.img > mkdir f2fs > mount f2fs_pin.img ./f2fs > cd f2fs > dd if=/dev/zero of=./large_padding bs=1M count=1760 > ./pin_filling.sh > rm padding* > sync > touch fallocate_40m > f2fs_io pinfile set fallocate_40m > fallocate -l 41943040 fallocate_40m > > fallocate always fail with EAGAIN even there has enough free space. > > 'pin_filling.sh' is: > count=1 > while : > do > # filling the seg space > for i in {1..511}: > do > name=padding_$count-$i > echo write $name > dd if=/dev/zero of=./$name bs=4K count=1 > /dev/null 2>&1 > if [ $? -ne 0 ]; then > exit 0 > fi > done > sync > > # pin one block in a segment > name=pin_file$count > dd if=/dev/zero of=./$name bs=4K count=1 > /dev/null 2>&1 > sync > f2fs_io pinfile set $name > count=$(($count + 1)) > done > > Signed-off-by: Wu Bo <bo.wu@vivo.com> > --- > fs/f2fs/file.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index ca5904129b16..e8a13616543f 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -1690,7 +1690,7 @@ static int f2fs_expand_inode_data(struct inode *inode, loff_t offset, > .init_gc_type = FG_GC, > .should_migrate_blocks = false, > .err_gc_skipped = true, > - .nr_free_secs = 0 }; > + .nr_free_secs = 1 }; > pgoff_t pg_start, pg_end; > loff_t new_size; > loff_t off_end;
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