6.18-stable review patch. If anyone has any objections, please let me know.
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From: Xiaole He hexiaole1994@126.com
commit 27bf6a637b7613fc85fa6af468b7d612d78cd5c0 upstream.
The age extent cache uses last_blocks (derived from allocated_data_blocks) to determine data age. However, there's a conflict between the deletion marker (last_blocks=0) and legitimate last_blocks=0 cases when allocated_data_blocks overflows to 0 after reaching ULLONG_MAX.
In this case, valid extents are incorrectly skipped due to the "if (!tei->last_blocks)" check in __update_extent_tree_range().
This patch fixes the issue by: 1. Reserving ULLONG_MAX as an invalid/deletion marker 2. Limiting allocated_data_blocks to range [0, ULLONG_MAX-1] 3. Using F2FS_EXTENT_AGE_INVALID for deletion scenarios 4. Adjusting overflow age calculation from ULLONG_MAX to (ULLONG_MAX-1)
Reproducer (using a patched kernel with allocated_data_blocks initialized to ULLONG_MAX - 3 for quick testing):
Step 1: Mount and check initial state # dd if=/dev/zero of=/tmp/test.img bs=1M count=100 # mkfs.f2fs -f /tmp/test.img # mkdir -p /mnt/f2fs_test # mount -t f2fs -o loop,age_extent_cache /tmp/test.img /mnt/f2fs_test # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age" Allocated Data Blocks: 18446744073709551612 # ULLONG_MAX - 3 Inner Struct Count: tree: 1(0), node: 0
Step 2: Create files and write data to trigger overflow # touch /mnt/f2fs_test/{1,2,3,4}.txt; sync # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age" Allocated Data Blocks: 18446744073709551613 # ULLONG_MAX - 2 Inner Struct Count: tree: 5(0), node: 1
# dd if=/dev/urandom of=/mnt/f2fs_test/1.txt bs=4K count=1; sync # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age" Allocated Data Blocks: 18446744073709551614 # ULLONG_MAX - 1 Inner Struct Count: tree: 5(0), node: 2
# dd if=/dev/urandom of=/mnt/f2fs_test/2.txt bs=4K count=1; sync # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age" Allocated Data Blocks: 18446744073709551615 # ULLONG_MAX Inner Struct Count: tree: 5(0), node: 3
# dd if=/dev/urandom of=/mnt/f2fs_test/3.txt bs=4K count=1; sync # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age" Allocated Data Blocks: 0 # Counter overflowed! Inner Struct Count: tree: 5(0), node: 4
Step 3: Trigger the bug - next write should create node but gets skipped # dd if=/dev/urandom of=/mnt/f2fs_test/4.txt bs=4K count=1; sync # cat /sys/kernel/debug/f2fs/status | grep -A 4 "Block Age" Allocated Data Blocks: 1 Inner Struct Count: tree: 5(0), node: 4
Expected: node: 5 (new extent node for 4.txt) Actual: node: 4 (extent insertion was incorrectly skipped due to last_blocks = allocated_data_blocks = 0 in __get_new_block_age)
After this fix, the extent node is correctly inserted and node count becomes 5 as expected.
Fixes: 71644dff4811 ("f2fs: add block_age-based extent cache") Cc: stable@kernel.org Signed-off-by: Xiaole He hexiaole1994@126.com Reviewed-by: Chao Yu chao@kernel.org Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/f2fs/extent_cache.c | 5 +++-- fs/f2fs/f2fs.h | 6 ++++++ fs/f2fs/segment.c | 9 +++++++-- 3 files changed, 16 insertions(+), 4 deletions(-)
--- a/fs/f2fs/extent_cache.c +++ b/fs/f2fs/extent_cache.c @@ -808,7 +808,7 @@ static void __update_extent_tree_range(s } goto out_read_extent_cache; update_age_extent_cache: - if (!tei->last_blocks) + if (tei->last_blocks == F2FS_EXTENT_AGE_INVALID) goto out_read_extent_cache;
__set_extent_info(&ei, fofs, len, 0, false, @@ -912,7 +912,7 @@ static int __get_new_block_age(struct in cur_age = cur_blocks - tei.last_blocks; else /* allocated_data_blocks overflow */ - cur_age = ULLONG_MAX - tei.last_blocks + cur_blocks; + cur_age = (ULLONG_MAX - 1) - tei.last_blocks + cur_blocks;
if (tei.age) ei->age = __calculate_block_age(sbi, cur_age, tei.age); @@ -1114,6 +1114,7 @@ void f2fs_update_age_extent_cache_range( struct extent_info ei = { .fofs = fofs, .len = len, + .last_blocks = F2FS_EXTENT_AGE_INVALID, };
if (!__may_extent_tree(dn->inode, EX_BLOCK_AGE)) --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -708,6 +708,12 @@ enum extent_type { NR_EXTENT_CACHES, };
+/* + * Reserved value to mark invalid age extents, hence valid block range + * from 0 to ULLONG_MAX-1 + */ +#define F2FS_EXTENT_AGE_INVALID ULLONG_MAX + struct extent_info { unsigned int fofs; /* start offset in a file */ unsigned int len; /* length of the extent */ --- a/fs/f2fs/segment.c +++ b/fs/f2fs/segment.c @@ -3881,8 +3881,13 @@ skip_new_segment: locate_dirty_segment(sbi, GET_SEGNO(sbi, old_blkaddr)); locate_dirty_segment(sbi, GET_SEGNO(sbi, *new_blkaddr));
- if (IS_DATASEG(curseg->seg_type)) - atomic64_inc(&sbi->allocated_data_blocks); + if (IS_DATASEG(curseg->seg_type)) { + unsigned long long new_val; + + new_val = atomic64_inc_return(&sbi->allocated_data_blocks); + if (unlikely(new_val == ULLONG_MAX)) + atomic64_set(&sbi->allocated_data_blocks, 0); + }
up_write(&sit_i->sentry_lock);