Commit 677017d1 authored by Sahitya Tummala's avatar Sahitya Tummala Committed by Jaegeuk Kim
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f2fs: Fix deadlock in f2fs_gc() context during atomic files handling 



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: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarSahitya Tummala <stummala@codeaurora.org>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent c45d6002

fs/f2fs/f2fs.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */

fs/f2fs/file.c

+1 −0
Original line number Diff line number Diff line
@@ -1922,6 +1922,7 @@ 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 */

fs/f2fs/segment.c

+15 −6
Original line number Diff line number Diff line
@@ -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 @@ next: 
	}

	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;

			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;

}
@@ -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]);

}

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