On 2019/11/8 19:03, Sahitya Tummala wrote:
> There could be a potential deadlock when the storage capacity
> is almost full and theren't enough free segments available, due
> to which FG_GC is needed in the atomic commit ioctl as shown in
> the below callstack -
>
> 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
>
> If this inode doesn't have i_gc_failures[GC_FAILURE_ATOMIC] set,
> then it waits forever in f2fs_drop_inmem_pages_all(), for this
> atomic inode to be dropped. And the rest of the system is stuck
> waiting for sbi->gc_mutex lock, which is acquired by f2fs_balance_fs()
> in the stack above.
I think the root cause of this issue is there is potential infinite loop in
f2fs_drop_inmem_pages_all() for the case of gc_failure is true, because once the
first inode in inode_list[ATOMIC_FILE] list didn't suffer gc failure, we will
skip dropping its in-memory cache and calling iput(), and traverse the list
again, most possibly there is the same inode in the head of that list.
Could you please check below fix:
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 7bf7b0194944..8a3a35b42a37 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1395,6 +1395,7 @@ 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 ecd063239642..79f4b348951a 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2047,6 +2047,7 @@ 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 8b977bbd6822..6aa0bb693697 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 +298,29 @@ 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)
+ return;
+ }
+
goto next;
}
@@ -334,6 +343,7 @@ void f2fs_drop_inmem_pages(struct inode *inode)
spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
if (!list_empty(&fi->inmem_ilist))
list_del_init(&fi->inmem_ilist);
+ sbi->atomic_files--;
spin_unlock(&sbi->inode_lock[ATOMIC_FILE]);
}
Thanks,
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