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 merging the dentry block check into the main data/node block
check loop and checking data_blocks + dent_blocks for data segments,
since both regular data blocks and dentry blocks can be written to the
same segment. When active_logs == 6, dentry blocks can be allocated to
any of the three data segments (HOT, WARM, COLD), so all three segments
need to account for dentry blocks. When active_logs != 6, dentry blocks
are always allocated to HOT_DATA segment only, so only HOT_DATA segment
needs to account for dentry blocks, while WARM and COLD segments only
check data_blocks.
Fixes: ef095d19e82f ("f2fs: write small sized IO to hot log")
Cc: [email protected]
Signed-off-by: Xiaole He <[email protected]>
---
Changes in v2 (per Yongpeng's feedback):
- Merged dentry block check into the main loop to avoid duplication
- Check data_blocks + dent_blocks for data segments (both can write to same
segment)
---
fs/f2fs/segment.h | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index 1ce2c8abaf48..acda720a54eb 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -626,21 +626,21 @@ static inline bool has_curseg_enough_space(struct
f2fs_sb_info *sbi,
left_blocks = get_left_section_blocks(sbi, i, segno);
- blocks = i <= CURSEG_COLD_DATA ? data_blocks : node_blocks;
+ if (i <= CURSEG_COLD_DATA) {
+ blocks = data_blocks;
+ /*
+ * With active_logs == 6, dentry blocks can be
allocated to
+ * any data segment. With active_logs != 6, dentry
blocks
+ * are always allocated to HOT_DATA segment.
+ */
+ if ((F2FS_OPTION(sbi).active_logs == 6) || (i ==
CURSEG_HOT_DATA))
+ blocks += dent_blocks;
+ } else {
+ blocks = node_blocks;
+ }
if (blocks > left_blocks)
return false;
}
-
- /* check current data section for dentry blocks. */
- segno = CURSEG_I(sbi, CURSEG_HOT_DATA)->segno;
-
- if (unlikely(segno == NULL_SEGNO))
- return false;
-
- left_blocks = get_left_section_blocks(sbi, CURSEG_HOT_DATA, segno);
-
- if (dent_blocks > left_blocks)
- return false;
return true;
}
