On 2018/7/30 9:32, Jaegeuk Kim wrote: > The f2fs_gc() called by f2fs_balance_fs() requires to be called outside of > fi->i_gc_rwsem[WRITE], since f2fs_gc() can try to grab it in a loop. > > If it hits the miximum retrials in GC, let's give a chance to release > gc_mutex for a short time in order not to go into live lock in the worst > case. > > Signed-off-by: Jaegeuk Kim <jaeg...@kernel.org> > --- > fs/f2fs/f2fs.h | 1 + > fs/f2fs/file.c | 62 ++++++++++++++++++++++------------------------- > fs/f2fs/gc.c | 22 ++++++++++++----- > fs/f2fs/segment.c | 5 +++- > fs/f2fs/segment.h | 2 +- > 5 files changed, 51 insertions(+), 41 deletions(-) > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index a9447c7d6570..50349780001b 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -1223,6 +1223,7 @@ struct f2fs_sb_info { > unsigned int gc_mode; /* current GC state */ > /* for skip statistic */ > unsigned long long skipped_atomic_files[2]; /* FG_GC and BG_GC */ > + unsigned long long skipped_gc_rwsem; /* FG_GC only */ > > /* threshold for gc trials on pinned files */ > u64 gc_pin_file_threshold; > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index 78c1bd6b8497..2b7d26ebb294 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -1179,10 +1179,12 @@ static int __exchange_data_block(struct inode > *src_inode, > return ret; > } > > -static int f2fs_do_collapse(struct inode *inode, pgoff_t start, pgoff_t end) > +static int f2fs_do_collapse(struct inode *inode, loff_t offset, loff_t len) > { > struct f2fs_sb_info *sbi = F2FS_I_SB(inode); > pgoff_t nrpages = (i_size_read(inode) + PAGE_SIZE - 1) / PAGE_SIZE; > + pgoff_t start = offset >> PAGE_SHIFT; > + pgoff_t end = (offset + len) >> PAGE_SHIFT; > int ret; > > f2fs_balance_fs(sbi, true); > @@ -1190,14 +1192,18 @@ static int f2fs_do_collapse(struct inode *inode, > pgoff_t start, pgoff_t end) > > f2fs_drop_extent_tree(inode); > > + /* avoid gc operation during block exchange */ > + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > + truncate_pagecache(inode, offset); > ret = __exchange_data_block(inode, inode, end, start, nrpages - end, > true); > + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > + > f2fs_unlock_op(sbi); > return ret; > } > > static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t > len) > { > - pgoff_t pg_start, pg_end; > loff_t new_size; > int ret; > > @@ -1212,21 +1218,13 @@ static int f2fs_collapse_range(struct inode *inode, > loff_t offset, loff_t len) > if (ret) > return ret; > > - pg_start = offset >> PAGE_SHIFT; > - pg_end = (offset + len) >> PAGE_SHIFT; > - > - /* avoid gc operation during block exchange */ > - down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > - > down_write(&F2FS_I(inode)->i_mmap_sem); > /* write out all dirty pages from offset */ > ret = filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX); > if (ret) > goto out_unlock; > > - truncate_pagecache(inode, offset); > - > - ret = f2fs_do_collapse(inode, pg_start, pg_end); > + ret = f2fs_do_collapse(inode, offset, len); > if (ret) > goto out_unlock; > > @@ -1242,7 +1240,6 @@ static int f2fs_collapse_range(struct inode *inode, > loff_t offset, loff_t len) > f2fs_i_size_write(inode, new_size); > out_unlock: > up_write(&F2FS_I(inode)->i_mmap_sem); > - up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > return ret; > } > > @@ -1417,9 +1414,6 @@ static int f2fs_insert_range(struct inode *inode, > loff_t offset, loff_t len) > > f2fs_balance_fs(sbi, true); > > - /* avoid gc operation during block exchange */ > - down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > - > down_write(&F2FS_I(inode)->i_mmap_sem); > ret = f2fs_truncate_blocks(inode, i_size_read(inode), true); > if (ret) > @@ -1430,13 +1424,15 @@ static int f2fs_insert_range(struct inode *inode, > loff_t offset, loff_t len) > if (ret) > goto out; > > - truncate_pagecache(inode, offset); > - > pg_start = offset >> PAGE_SHIFT; > pg_end = (offset + len) >> PAGE_SHIFT; > delta = pg_end - pg_start; > idx = (i_size_read(inode) + PAGE_SIZE - 1) / PAGE_SIZE; > > + /* avoid gc operation during block exchange */ > + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > + truncate_pagecache(inode, offset); > + > while (!ret && idx > pg_start) { > nr = idx - pg_start; > if (nr > delta) > @@ -1450,6 +1446,7 @@ static int f2fs_insert_range(struct inode *inode, > loff_t offset, loff_t len) > idx + delta, nr, false); > f2fs_unlock_op(sbi); > } > + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > > /* write out all moved pages, if possible */ > filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX); > @@ -1459,7 +1456,6 @@ static int f2fs_insert_range(struct inode *inode, > loff_t offset, loff_t len) > f2fs_i_size_write(inode, new_size); > out: > up_write(&F2FS_I(inode)->i_mmap_sem); > - up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > return ret; > } > > @@ -1706,8 +1702,6 @@ static int f2fs_ioc_start_atomic_write(struct file > *filp) > > inode_lock(inode); > > - down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
After removing lock here, how can we handle below condition: commit 27319ba4044c0c67d62ae39e53c0118c89f0a029 Author: Chao Yu <yuch...@huawei.com> Date: Tue Apr 17 17:51:28 2018 +0800 f2fs: fix race in between GC and atomic open Thread GC thread - f2fs_ioc_start_atomic_write - get_dirty_pages - filemap_write_and_wait_range - f2fs_gc - do_garbage_collect - gc_data_segment - move_data_page - f2fs_is_atomic_file - set_page_dirty - set_inode_flag(, FI_ATOMIC_FILE) Dirty data page can still be generated by GC in race condition as above call stack. This patch adds fi->dio_rwsem[WRITE] in f2fs_ioc_start_atomic_write to avoid such race. Thanks, > - > if (f2fs_is_atomic_file(inode)) { > if (is_inode_flag_set(inode, FI_ATOMIC_REVOKE_REQUEST)) > ret = -EINVAL; > @@ -1736,7 +1730,6 @@ static int f2fs_ioc_start_atomic_write(struct file > *filp) > stat_inc_atomic_write(inode); > stat_update_max_atomic_write(inode); > out: > - up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > inode_unlock(inode); > mnt_drop_write_file(filp); > return ret; > @@ -1754,9 +1747,9 @@ static int f2fs_ioc_commit_atomic_write(struct file > *filp) > if (ret) > return ret; > > - inode_lock(inode); > + f2fs_balance_fs(F2FS_I_SB(inode), true); > > - down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > + inode_lock(inode); > > if (f2fs_is_volatile_file(inode)) { > ret = -EINVAL; > @@ -1782,7 +1775,6 @@ static int f2fs_ioc_commit_atomic_write(struct file > *filp) > clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST); > ret = -EINVAL; > } > - up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > inode_unlock(inode); > mnt_drop_write_file(filp); > return ret; > @@ -2378,15 +2370,10 @@ static int f2fs_move_file_range(struct file *file_in, > loff_t pos_in, > } > > inode_lock(src); > - down_write(&F2FS_I(src)->i_gc_rwsem[WRITE]); > if (src != dst) { > ret = -EBUSY; > if (!inode_trylock(dst)) > goto out; > - if (!down_write_trylock(&F2FS_I(dst)->i_gc_rwsem[WRITE])) { > - inode_unlock(dst); > - goto out; > - } > } > > ret = -EINVAL; > @@ -2432,6 +2419,14 @@ static int f2fs_move_file_range(struct file *file_in, > loff_t pos_in, > > f2fs_balance_fs(sbi, true); > f2fs_lock_op(sbi); > + > + down_write(&F2FS_I(src)->i_gc_rwsem[WRITE]); > + if (src != dst) { > + ret = -EBUSY; > + if (!down_write_trylock(&F2FS_I(dst)->i_gc_rwsem[WRITE])) > + goto out_src; > + } > + > ret = __exchange_data_block(src, dst, pos_in >> F2FS_BLKSIZE_BITS, > pos_out >> F2FS_BLKSIZE_BITS, > len >> F2FS_BLKSIZE_BITS, false); > @@ -2442,14 +2437,15 @@ static int f2fs_move_file_range(struct file *file_in, > loff_t pos_in, > else if (dst_osize != dst->i_size) > f2fs_i_size_write(dst, dst_osize); > } > + if (src != dst) > + up_write(&F2FS_I(dst)->i_gc_rwsem[WRITE]); > +out_src: > + up_write(&F2FS_I(src)->i_gc_rwsem[WRITE]); > f2fs_unlock_op(sbi); > out_unlock: > - if (src != dst) { > - up_write(&F2FS_I(dst)->i_gc_rwsem[WRITE]); > + if (src != dst) > inode_unlock(dst); > - } > out: > - up_write(&F2FS_I(src)->i_gc_rwsem[WRITE]); > inode_unlock(src); > return ret; > } > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c > index e352fbd33848..cac317e37306 100644 > --- a/fs/f2fs/gc.c > +++ b/fs/f2fs/gc.c > @@ -884,6 +884,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, > struct f2fs_summary *sum, > if (!down_write_trylock( > &F2FS_I(inode)->i_gc_rwsem[WRITE])) { > iput(inode); > + sbi->skipped_gc_rwsem++; > continue; > } > > @@ -913,6 +914,7 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, > struct f2fs_summary *sum, > continue; > if (!down_write_trylock( > &fi->i_gc_rwsem[WRITE])) { > + sbi->skipped_gc_rwsem++; > up_write(&fi->i_gc_rwsem[READ]); > continue; > } > @@ -1062,6 +1064,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, > prefree_segments(sbi)); > > cpc.reason = __get_cp_reason(sbi); > + sbi->skipped_gc_rwsem = 0; > gc_more: > if (unlikely(!(sbi->sb->s_flags & SB_ACTIVE))) { > ret = -EINVAL; > @@ -1103,7 +1106,8 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, > total_freed += seg_freed; > > if (gc_type == FG_GC) { > - if (sbi->skipped_atomic_files[FG_GC] > last_skipped) > + if (sbi->skipped_atomic_files[FG_GC] > last_skipped || > + sbi->skipped_gc_rwsem) > skipped_round++; > last_skipped = sbi->skipped_atomic_files[FG_GC]; > round++; > @@ -1112,15 +1116,21 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, > if (gc_type == FG_GC) > sbi->cur_victim_sec = NULL_SEGNO; > > - if (!sync) { > - if (has_not_enough_free_secs(sbi, sec_freed, 0)) { > - if (skipped_round > MAX_SKIP_ATOMIC_COUNT && > - skipped_round * 2 >= round) > - f2fs_drop_inmem_pages_all(sbi, true); > + if (sync) > + goto stop; > + > + if (has_not_enough_free_secs(sbi, sec_freed, 0)) { > + if (skipped_round <= MAX_SKIP_GC_COUNT || > + skipped_round * 2 < round) { > segno = NULL_SEGNO; > goto gc_more; > } > > + if (sbi->skipped_atomic_files[FG_GC] == last_skipped) { > + f2fs_drop_inmem_pages_all(sbi, true); > + segno = NULL_SEGNO; > + goto gc_more; > + } > if (gc_type == FG_GC) > ret = f2fs_write_checkpoint(sbi, &cpc); > } > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index 3662e1f429b4..15b3b095fd58 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -444,10 +444,12 @@ int f2fs_commit_inmem_pages(struct inode *inode) > struct f2fs_inode_info *fi = F2FS_I(inode); > int err; > > - f2fs_balance_fs(sbi, true); > + f2fs_balance_fs(F2FS_I_SB(inode), true); > + > f2fs_lock_op(sbi); > > set_inode_flag(inode, FI_ATOMIC_COMMIT); > + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > > mutex_lock(&fi->inmem_lock); > err = __f2fs_commit_inmem_pages(inode); > @@ -458,6 +460,7 @@ int f2fs_commit_inmem_pages(struct inode *inode) > spin_unlock(&sbi->inode_lock[ATOMIC_FILE]); > mutex_unlock(&fi->inmem_lock); > > + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > clear_inode_flag(inode, FI_ATOMIC_COMMIT); > > f2fs_unlock_op(sbi); > diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h > index 50495515f0a0..b3d9e317ff0c 100644 > --- a/fs/f2fs/segment.h > +++ b/fs/f2fs/segment.h > @@ -215,7 +215,7 @@ struct segment_allocation { > #define IS_DUMMY_WRITTEN_PAGE(page) \ > (page_private(page) == (unsigned long)DUMMY_WRITTEN_PAGE) > > -#define MAX_SKIP_ATOMIC_COUNT 16 > +#define MAX_SKIP_GC_COUNT 16 > > struct inmem_pages { > struct list_head list; 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