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| author | Jan Kara <jack@suse.cz> | 2023-05-04 14:47:23 +0200 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2023-05-14 00:05:04 +0200 |
| commit | 00d873c17e29cc32d90ca852b82685f1673acaa5 (patch) | |
| tree | b1069936b04e0b527980038cb415812eaa11a64e /fs/ext4/migrate.c | |
| parent | ext4: fix invalid free tracking in ext4_xattr_move_to_block() (diff) | |
| download | linux-00d873c17e29cc32d90ca852b82685f1673acaa5.tar.xz linux-00d873c17e29cc32d90ca852b82685f1673acaa5.zip | |
ext4: avoid deadlock in fs reclaim with page writeback
Ext4 has a filesystem wide lock protecting ext4_writepages() calls to
avoid races with switching of journalled data flag or inode format. This
lock can however cause a deadlock like:
CPU0 CPU1
ext4_writepages()
percpu_down_read(sbi->s_writepages_rwsem);
ext4_change_inode_journal_flag()
percpu_down_write(sbi->s_writepages_rwsem);
- blocks, all readers block from now on
ext4_do_writepages()
ext4_init_io_end()
kmem_cache_zalloc(io_end_cachep, GFP_KERNEL)
fs_reclaim frees dentry...
dentry_unlink_inode()
iput() - last ref =>
iput_final() - inode dirty =>
write_inode_now()...
ext4_writepages() tries to acquire sbi->s_writepages_rwsem
and blocks forever
Make sure we cannot recurse into filesystem reclaim from writeback code
to avoid the deadlock.
Reported-by: syzbot+6898da502aef574c5f8a@syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/0000000000004c66b405fa108e27@google.com
Fixes: c8585c6fcaf2 ("ext4: fix races between changing inode journal mode and ext4_writepages")
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230504124723.20205-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to '')
| -rw-r--r-- | fs/ext4/migrate.c | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c index a19a9661646e..d98ac2af8199 100644 --- a/fs/ext4/migrate.c +++ b/fs/ext4/migrate.c @@ -408,7 +408,6 @@ static int free_ext_block(handle_t *handle, struct inode *inode) int ext4_ext_migrate(struct inode *inode) { - struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); handle_t *handle; int retval = 0, i; __le32 *i_data; @@ -418,6 +417,7 @@ int ext4_ext_migrate(struct inode *inode) unsigned long max_entries; __u32 goal, tmp_csum_seed; uid_t owner[2]; + int alloc_ctx; /* * If the filesystem does not support extents, or the inode @@ -434,7 +434,7 @@ int ext4_ext_migrate(struct inode *inode) */ return retval; - percpu_down_write(&sbi->s_writepages_rwsem); + alloc_ctx = ext4_writepages_down_write(inode->i_sb); /* * Worst case we can touch the allocation bitmaps and a block @@ -586,7 +586,7 @@ out_tmp_inode: unlock_new_inode(tmp_inode); iput(tmp_inode); out_unlock: - percpu_up_write(&sbi->s_writepages_rwsem); + ext4_writepages_up_write(inode->i_sb, alloc_ctx); return retval; } @@ -605,6 +605,7 @@ int ext4_ind_migrate(struct inode *inode) ext4_fsblk_t blk; handle_t *handle; int ret, ret2 = 0; + int alloc_ctx; if (!ext4_has_feature_extents(inode->i_sb) || (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) @@ -621,7 +622,7 @@ int ext4_ind_migrate(struct inode *inode) if (test_opt(inode->i_sb, DELALLOC)) ext4_alloc_da_blocks(inode); - percpu_down_write(&sbi->s_writepages_rwsem); + alloc_ctx = ext4_writepages_down_write(inode->i_sb); handle = ext4_journal_start(inode, EXT4_HT_MIGRATE, 1); if (IS_ERR(handle)) { @@ -665,6 +666,6 @@ errout: ext4_journal_stop(handle); up_write(&EXT4_I(inode)->i_data_sem); out_unlock: - percpu_up_write(&sbi->s_writepages_rwsem); + ext4_writepages_up_write(inode->i_sb, alloc_ctx); return ret; } |