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? > > > > >> 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
