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Mon, 10 Nov 2025 18:44:59 -0800 (PST) Message-ID: <3a787685-1765-4068-a8da-d595dd257b71@gmail.com> Date: Tue, 11 Nov 2025 10:44:54 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [f2fs-dev] [PATCH v1] f2fs: fix has_curseg_enough_space to check all data segments for dentry blocks To: Xiaole He , linux-f2fs-devel@lists.sourceforge.net Cc: jaegeuk@kernel.org, linux-kernel@vger.kernel.org, stable@kernel.org, Yongpeng Yang References: <20251110132654.6485-1-hexiaole1994@126.com> Content-Language: en-US From: Yongpeng Yang In-Reply-To: <20251110132654.6485-1-hexiaole1994@126.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11/10/25 21:26, Xiaole He wrote: > When active_logs == 6, dentry blocks can be allocated to HOT, WARM, or > COLD segments based on various conditions in __get_segment_type_6(): > - age extent cache (if enabled) > - FI_HOT_DATA flag (set when dirty_pages <= min_hot_blocks) > - rw_hint (defaults to WARM via f2fs_rw_hint_to_seg_type) > - file_is_hot(), FI_NEED_IPU, f2fs_is_cow_file(), etc. > > However, has_curseg_enough_space() only checked CURSEG_HOT_DATA segment > for dentry blocks, which could lead to incorrect space calculation when > dentry blocks are actually allocated to WARM or COLD segments. > > Reproducer: > Note: This reproducer requires adding a tracepoint to observe segment > type. Add the following tracepoint to include/trace/events/f2fs.h: > > TRACE_EVENT(f2fs_allocate_data_block, > TP_PROTO(struct f2fs_sb_info *sbi, struct inode *inode, > enum log_type type, block_t blkaddr), > > TP_ARGS(sbi, inode, type, blkaddr), > > TP_STRUCT__entry( > __field(dev_t, dev) > __field(ino_t, ino) > __field(int, type) > __field(block_t, blkaddr) > __field(int, is_dir) > ), > > TP_fast_assign( > __entry->dev = sbi->sb->s_dev; > __entry->ino = inode ? inode->i_ino : 0; > __entry->type = type; > __entry->blkaddr = blkaddr; > __entry->is_dir = inode ? S_ISDIR(inode->i_mode) : 0; > ), > > TP_printk("dev = (%d,%d), ino = %lu, %s, blkaddr = %u, is_dir = %d", > show_dev(__entry->dev), > (unsigned long)__entry->ino, > show_data_type(__entry->type), > __entry->blkaddr, > __entry->is_dir) > ); > > And add the tracepoint call in fs/f2fs/segment.c in > f2fs_allocate_data_block() function. Find the location after > locate_dirty_segment() calls and before IS_DATASEG() check: > > locate_dirty_segment(sbi, GET_SEGNO(sbi, old_blkaddr)); > locate_dirty_segment(sbi, GET_SEGNO(sbi, *new_blkaddr)); > > trace_f2fs_allocate_data_block(sbi, folio ? folio->mapping->host : NULL, > type, *new_blkaddr); > > if (IS_DATASEG(curseg->seg_type)) > > 1. Mount F2FS with active_logs=6 and age extent cache disabled: > # mkfs.f2fs -f /dev/sdb1 > # mount -t f2fs -o active_logs=6 /dev/sdb1 /mnt/f2fs-test > > 2. Enable tracing and f2fs_allocate_data_block tracepoint: > # echo 1 > /sys/kernel/debug/tracing/events/f2fs/f2fs_allocate_data_block/enable > # echo 1 > /sys/kernel/debug/tracing/tracing_on > # echo > /sys/kernel/debug/tracing/trace > > 3. Create a directory and write enough files to trigger dirty_pages > > min_hot_blocks (default 16), which will clear FI_HOT_DATA flag: > # mkdir /mnt/f2fs-test/testdir > # cd /mnt/f2fs-test/testdir > # seq 1 8192 | xargs touch > # sync > > 4. Observe dentry block allocation: > # cat /sys/kernel/debug/tracing/trace > > The trace output shows dentry blocks (is_dir = 1) allocated to WARM > segment because FI_HOT_DATA is cleared when dirty_pages > > min_hot_blocks (default 16). However, has_curseg_enough_space() only > checked HOT_DATA segment space. > > Fix by checking all three data segments (HOT, WARM, COLD) when > active_logs == 6, similar to how __get_segment_type_6() can return > any of these segment types for dentry blocks. > > Fixes: ef095d19e82f ("f2fs: write small sized IO to hot log") > Cc: stable@kernel.org > Signed-off-by: Xiaole He > --- > fs/f2fs/segment.h | 31 +++++++++++++++++++++++++------ > 1 file changed, 25 insertions(+), 6 deletions(-) > > diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h > index 1ce2c8abaf48..c13400a53013 100644 > --- a/fs/f2fs/segment.h > +++ b/fs/f2fs/segment.h > @@ -632,15 +632,34 @@ static inline bool has_curseg_enough_space(struct f2fs_sb_info *sbi, > } > > /* check current data section for dentry blocks. */ > - segno = CURSEG_I(sbi, CURSEG_HOT_DATA)->segno; > + if (F2FS_OPTION(sbi).active_logs == 6) { > + /* > + * With active_logs == 6, dentry blocks can be allocated to > + * HOT, WARM, or COLD segments based on age extent cache, > + * FI_HOT_DATA flag, rw_hint, etc. Check all three. > + */ > + for (i = CURSEG_HOT_DATA; i <= CURSEG_COLD_DATA; i++) { > + segno = CURSEG_I(sbi, i)->segno; > + > + if (unlikely(segno == NULL_SEGNO)) > + return false; > + > + left_blocks = get_left_section_blocks(sbi, i, segno); > + > + if (dent_blocks > left_blocks) > + return false; > + } How about merging this for-loop with the one above to avoid duplicated code? Since both dent_blocks and data_blocks may write to data segments, should we also check whether data_blocks + dent_blocks > left_blocks? Yongpeng, > + } else { > + segno = CURSEG_I(sbi, CURSEG_HOT_DATA)->segno; > > - if (unlikely(segno == NULL_SEGNO)) > - return false; > + if (unlikely(segno == NULL_SEGNO)) > + return false; > > - left_blocks = get_left_section_blocks(sbi, CURSEG_HOT_DATA, segno); > + left_blocks = get_left_section_blocks(sbi, CURSEG_HOT_DATA, segno); > > - if (dent_blocks > left_blocks) > - return false; > + if (dent_blocks > left_blocks) > + return false; > + } > return true; > } >