On 07/29, Chao Yu wrote: > On 2018/7/29 10:02, Jaegeuk Kim wrote: > > On 07/27, Chao Yu wrote: > >> On 2018/7/27 18:29, Jaegeuk Kim wrote: > >>> On 07/26, Chao Yu wrote: > >>>> Thread A Background GC > >>>> - f2fs_zero_range > >>>> - truncate_pagecache_range > >>>> - gc_data_segment > >>>> - get_read_data_page > >>>> - move_data_page > >>>> - set_page_dirty > >>>> - set_cold_data > >>>> - f2fs_do_zero_range > >>>> - dn->data_blkaddr = NEW_ADDR; > >>>> - f2fs_set_data_blkaddr > >>>> > >>>> Actually, we don't need to set dirty & checked flag on the page, since > >>>> all valid data in the page should be zeroed by zero_range(). > >>> > >>> But, it doesn't matter too much, right? > >> > >> No, if the dirtied page is writebacked after f2fs_do_zero_range(), result > >> of > >> zero_range() should be wrong, as zeroed page contains valid user data. > > > > How about truncating page caches after block address change or doing it > > twice > > before and after? > > Thread A Background GC > - f2fs_zero_range > - truncate_pagecache_range > - gc_data_segment > - get_read_data_page > - move_data_page > - set_page_dirty > - set_cold_data > - f2fs_do_zero_range > - dn->data_blkaddr = NEW_ADDR; > - f2fs_set_data_blkaddr > bdi-flusher > - __write_data_page > - f2fs_update_data_blkaddr > : data_blkaddr has been updated here. > - truncate_pagecache_range > : data & dnode has been writebacked before page cache truncation? > > How about this case?
So, truncating pages under dnode lock can address it? > > Thanks, > > > > >> > >>> > >>>> Use i_gc_rwsem[WRITE] to avoid such race condition. > >>> > >>> Hope to avoid abusing i_gc_rwsem[] tho. > >> > >> Agreed, let's try avoiding until we have to use it. > >> > >> Thanks, > >> > >>> > >>>> > >>>> Signed-off-by: Chao Yu <yuch...@huawei.com> > >>>> --- > >>>> fs/f2fs/file.c | 2 ++ > >>>> 1 file changed, 2 insertions(+) > >>>> > >>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > >>>> index 267ec3794e1e..7bd2412a8c37 100644 > >>>> --- a/fs/f2fs/file.c > >>>> +++ b/fs/f2fs/file.c > >>>> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, > >>>> loff_t offset, loff_t len, > >>>> if (ret) > >>>> return ret; > >>>> > >>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >>>> down_write(&F2FS_I(inode)->i_mmap_sem); > >>>> ret = filemap_write_and_wait_range(mapping, offset, offset + > >>>> len - 1); > >>>> if (ret) > >>>> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, > >>>> loff_t offset, loff_t len, > >>>> } > >>>> out_sem: > >>>> up_write(&F2FS_I(inode)->i_mmap_sem); > >>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > >>>> > >>>> return ret; > >>>> } > >>>> -- > >>>> 2.18.0.rc1 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
