On 11/13, Sahitya Tummala wrote:
> The FS got stuck in the below stack when the storage is almost
> full/dirty condition (when FG_GC is being done).
>
> schedule_timeout
> io_schedule_timeout
> congestion_wait
> f2fs_drop_inmem_pages_all
> f2fs_gc
> f2fs_balance_fs
> __write_node_page
> f2fs_fsync_node_pages
> f2fs_do_sync_file
> f2fs_ioctl
>
> The root cause for this issue is there is a potential infinite loop
> in f2fs_drop_inmem_pages_all() for the case where gc_failure is true
> and when there an inode whose i_gc_failures[GC_FAILURE_ATOMIC] is
> not set. Fix this by keeping track of the total atomic files
> currently opened and using that to exit from this condition.
>
> Fix-suggested-by: Chao Yu <yuch...@huawei.com>
> Signed-off-by: Chao Yu <yuch...@huawei.com>
> Signed-off-by: Sahitya Tummala <stumm...@codeaurora.org>
> ---
> v2:
> - change fix as per Chao's suggestion
> - decrement sbi->atomic_files protected under sbi->inode_lock[ATOMIC_FILE] and
> only when atomic flag is cleared for the first time, otherwise, the count
> goes to an invalid/high value as f2fs_drop_inmem_pages() can be called from
> two contexts at the same time.
>
> fs/f2fs/f2fs.h | 1 +
> fs/f2fs/file.c | 1 +
> fs/f2fs/segment.c | 21 +++++++++++++++------
> 3 files changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index c681f51..e04a665 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1297,6 +1297,7 @@ struct f2fs_sb_info {
> unsigned int gc_mode; /* current GC state */
> unsigned int next_victim_seg[2]; /* next segment in victim
> section */
> /* for skip statistic */
> + unsigned int atomic_files; /* # of opened atomic file */
> unsigned long long skipped_atomic_files[2]; /* FG_GC and BG_GC */
> unsigned long long skipped_gc_rwsem; /* FG_GC only */
>
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index f6c038e..22c4949 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1919,6 +1919,7 @@ static int f2fs_ioc_start_atomic_write(struct file
> *filp)
> spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> if (list_empty(&fi->inmem_ilist))
> list_add_tail(&fi->inmem_ilist, &sbi->inode_list[ATOMIC_FILE]);
> + sbi->atomic_files++;
> spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>
> /* add inode in inmem_list first and set atomic_file */
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index da830fc..0b7a33b 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -288,6 +288,8 @@ void f2fs_drop_inmem_pages_all(struct f2fs_sb_info *sbi,
> bool gc_failure)
> struct list_head *head = &sbi->inode_list[ATOMIC_FILE];
> struct inode *inode;
> struct f2fs_inode_info *fi;
> + unsigned int count = sbi->atomic_files;
> + unsigned int looped = 0;
> next:
> spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> if (list_empty(head)) {
> @@ -296,22 +298,26 @@ void f2fs_drop_inmem_pages_all(struct f2fs_sb_info
> *sbi, bool gc_failure)
> }
> fi = list_first_entry(head, struct f2fs_inode_info, inmem_ilist);
> inode = igrab(&fi->vfs_inode);
> + if (inode)
> + list_move_tail(&fi->inmem_ilist, head);
> spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
>
> if (inode) {
> if (gc_failure) {
> - if (fi->i_gc_failures[GC_FAILURE_ATOMIC])
> - goto drop;
> - goto skip;
> + if (!fi->i_gc_failures[GC_FAILURE_ATOMIC])
> + goto skip;
> }
> -drop:
> set_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
> f2fs_drop_inmem_pages(inode);
> +skip:
> iput(inode);
> }
> -skip:
> congestion_wait(BLK_RW_ASYNC, HZ/50);
> cond_resched();
> + if (gc_failure) {
> + if (++looped >= count)
There is a race condition when handling sbi->atomic_files?
> + return;
> + }
> goto next;
> }
>
> @@ -327,13 +333,16 @@ void f2fs_drop_inmem_pages(struct inode *inode)
> mutex_unlock(&fi->inmem_lock);
> }
>
> - clear_inode_flag(inode, FI_ATOMIC_FILE);
> fi->i_gc_failures[GC_FAILURE_ATOMIC] = 0;
> stat_dec_atomic_write(inode);
>
> spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
> if (!list_empty(&fi->inmem_ilist))
> list_del_init(&fi->inmem_ilist);
> + if (f2fs_is_atomic_file(inode)) {
> + clear_inode_flag(inode, FI_ATOMIC_FILE);
> + sbi->atomic_files--;
> + }
> spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
> }
>
> --
> Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux
> Foundation Collaborative Project.
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