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. > >> 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
