On 2025/6/13 16:25, Zhiguo Niu wrote:
wangzijie <wangzij...@honor.com> 于2025年6月12日周四 20:38写道:

On 6/12/25 11:27, wangzijie wrote:
Wu Bo once mentioned a fallocate fail scenario in this link[1].
After commit 3fdd89b452c2("f2fs: prevent writing without fallocate()
for pinned files"), we cannot directly generate 4K size file and
pin it, but we can still generate non-segment aligned pinned file:

touch test_file
./f2fs_io pinfile set test_file
./f2fs_io fallocate 0 0 8192 test_file
truncate -s 4096 test_file

Well, shouldn't we avoid such case by adding check condition in setattr?

Maybe like this?

---
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 6bd3de64f..2f6537d9c 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1027,6 +1027,8 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry 
*dentry,
         struct inode *inode = d_inode(dentry);
         struct f2fs_inode_info *fi = F2FS_I(inode);
         int err;
+       struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+       block_t sec_blks = CAP_BLKS_PER_SEC(sbi);

         if (unlikely(f2fs_cp_error(F2FS_I_SB(inode))))
                 return -EIO;
@@ -1047,6 +1049,11 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry 
*dentry,
                         !IS_ALIGNED(attr->ia_size,
                         F2FS_BLK_TO_BYTES(fi->i_cluster_size)))
                         return -EINVAL;
+               if (f2fs_is_pinned_file(inode) &&
+                       attr->ia_size < i_size_read(inode) &&
+                       !IS_ALIGNED(attr->ia_size,
+                       F2FS_BLK_TO_BYTES(sec_blks)));
+                       return -EINVAL;
Hi Chao and zijie,
Excuse me ,I'm a bit confused about this:
when a pin file size is not alinged with size of "section", it can not
be truncated?

IMO, the pinned file can only be truncated to section-aligned size.

Thanks

thanks!
         }

         err = setattr_prepare(idmap, dentry, attr);
---


By doing this, pin+fallocate failure(gc happens EAGAIN but f2fs shows
enough spare space) may occurs.

 From message in commit 2e42b7f817ac("f2fs: stop allocating pinned sections
if EAGAIN happens"), gc EAGAIN doesn't guarantee a free section, so we stop
allocating. But after commit 48ea8b200414 ("f2fs: fix to avoid panic once
fallocation fails for pinfile"), we have a way to avoid panic caused by
concurrent pinfile allocation run out of free section, so I think that we
can continue to allocate pinned section when gc happens EAGAIN. Even if we
don't have free section, f2fs_allocate_pinning_section() can fail with ENOSPC.

What do you think of introduce /sys/fs/f2fs/<dev>/reserved_pin_section to
tune @needed parameter of has_not_enough_free_secs()? If we configure it
w/ zero, it can avoid f2fs_gc() before preallocation.

---
  fs/f2fs/f2fs.h  | 3 +++
  fs/f2fs/file.c  | 5 ++---
  fs/f2fs/super.c | 3 +++
  fs/f2fs/sysfs.c | 9 +++++++++
  4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 785537576aa8..ffb15da570d7 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1731,6 +1731,9 @@ struct f2fs_sb_info {
       /* for skip statistic */
       unsigned long long skipped_gc_rwsem;            /* FG_GC only */

+     /* free sections reserved for pinned file */
+     unsigned int reserved_pin_section;
+
       /* threshold for gc trials on pinned files */
       unsigned short gc_pin_file_threshold;
       struct f2fs_rwsem pin_sem;
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 696131e655ed..a909f79db178 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1887,9 +1887,8 @@ static int f2fs_expand_inode_data(struct inode *inode, 
loff_t offset,
                       }
               }

-             if (has_not_enough_free_secs(sbi, 0, f2fs_sb_has_blkzoned(sbi) ?
-                     ZONED_PIN_SEC_REQUIRED_COUNT :
-                     GET_SEC_FROM_SEG(sbi, overprovision_segments(sbi)))) {
+             if (has_not_enough_free_secs(sbi, 0,
+                             sbi->reserved_pin_section)) {
                       f2fs_down_write(&sbi->gc_lock);
                       stat_inc_gc_call_count(sbi, FOREGROUND);
                       err = f2fs_gc(sbi, &gc_control);
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 57adeff5ef25..48b97a95fd63 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -4975,6 +4975,9 @@ static int f2fs_fill_super(struct super_block *sb, struct 
fs_context *fc)
       sbi->last_valid_block_count = sbi->total_valid_block_count;
       sbi->reserved_blocks = 0;
       sbi->current_reserved_blocks = 0;
+     sbi->reserved_pin_section = f2fs_sb_has_blkzoned(sbi) ?
+                     ZONED_PIN_SEC_REQUIRED_COUNT :
+                     GET_SEC_FROM_SEG(sbi, overprovision_segments(sbi));
       limit_reserve_root(sbi);
       adjust_unusable_cap_perc(sbi);

diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 75134d69a0bd..51be7ffb38c5 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -824,6 +824,13 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
               return count;
       }

+     if (!strcmp(a->attr.name, "reserved_pin_section")) {
+             if (t > GET_SEC_FROM_SEG(sbi, overprovision_segments(sbi)))
+                     return -EINVAL;
+             *ui = (unsigned int)t;
+             return count;
+     }
+
       *ui = (unsigned int)t;

       return count;
@@ -1130,6 +1137,7 @@ F2FS_SBI_GENERAL_RO_ATTR(unusable_blocks_per_sec);
  F2FS_SBI_GENERAL_RW_ATTR(blkzone_alloc_policy);
  #endif
  F2FS_SBI_GENERAL_RW_ATTR(carve_out);
+F2FS_SBI_GENERAL_RW_ATTR(reserved_pin_section);

  /* STAT_INFO ATTR */
  #ifdef CONFIG_F2FS_STAT_FS
@@ -1323,6 +1331,7 @@ static struct attribute *f2fs_attrs[] = {
       ATTR_LIST(last_age_weight),
       ATTR_LIST(max_read_extent_count),
       ATTR_LIST(carve_out),
+     ATTR_LIST(reserved_pin_section),
       NULL,
  };
  ATTRIBUTE_GROUPS(f2fs);
--
2.49.0

I think it's a good way to solve this problem. Thank you!



[1] 
https://lore.kernel.org/linux-f2fs-devel/20231030094024.263707-1-bo...@vivo.com/t/#u

Signed-off-by: wangzijie <wangzij...@honor.com>
---
  fs/f2fs/file.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 6bd3de64f..05c80d2b5 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1859,7 +1859,7 @@ static int f2fs_expand_inode_data(struct inode *inode, 
loff_t offset,
                     f2fs_down_write(&sbi->gc_lock);
                     stat_inc_gc_call_count(sbi, FOREGROUND);
                     err = f2fs_gc(sbi, &gc_control);
-                   if (err && err != -ENODATA) {
+                   if (err && err != -ENODATA && err != -EAGAIN) {
                             f2fs_up_write(&sbi->pin_sem);
                             goto out_err;
                     }



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