From 34cf865d54813aab3497838132fb1bbd293f4054 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Wed, 18 Dec 2013 00:44:44 -0500 Subject: [PATCH] ext4: fix deadlock when writing in ENOSPC conditions Akira-san has been reporting rare deadlocks of his machine when running xfstests test 269 on ext4 filesystem. The problem turned out to be in ext4_da_reserve_metadata() and ext4_da_reserve_space() which called ext4_should_retry_alloc() while holding i_data_sem. Since ext4_should_retry_alloc() can force a transaction commit, this is a lock ordering violation and leads to deadlocks. Fix the problem by just removing the retry loops. These functions should just report ENOSPC to the caller (e.g. ext4_da_write_begin()) and that function must take care of retrying after dropping all necessary locks. Reported-and-tested-by: Akira Fujita Reviewed-by: Zheng Liu Signed-off-by: Jan Kara Signed-off-by: "Theodore Ts'o" Cc: stable@vger.kernel.org --- fs/ext4/inode.c | 12 ------------ 1 file changed, 12 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 0757634..61d49ff 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1206,7 +1206,6 @@ static int ext4_journalled_write_end(struct file *file, */ static int ext4_da_reserve_metadata(struct inode *inode, ext4_lblk_t lblock) { - int retries = 0; struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); struct ext4_inode_info *ei = EXT4_I(inode); unsigned int md_needed; @@ -1218,7 +1217,6 @@ static int ext4_da_reserve_metadata(struct inode *inode, ext4_lblk_t lblock) * in order to allocate nrblocks * worse case is one extent per block */ -repeat: spin_lock(&ei->i_block_reservation_lock); /* * ext4_calc_metadata_amount() has side effects, which we have @@ -1238,10 +1236,6 @@ repeat: ei->i_da_metadata_calc_len = save_len; ei->i_da_metadata_calc_last_lblock = save_last_lblock; spin_unlock(&ei->i_block_reservation_lock); - if (ext4_should_retry_alloc(inode->i_sb, &retries)) { - cond_resched(); - goto repeat; - } return -ENOSPC; } ei->i_reserved_meta_blocks += md_needed; @@ -1255,7 +1249,6 @@ repeat: */ static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock) { - int retries = 0; struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); struct ext4_inode_info *ei = EXT4_I(inode); unsigned int md_needed; @@ -1277,7 +1270,6 @@ static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock) * in order to allocate nrblocks * worse case is one extent per block */ -repeat: spin_lock(&ei->i_block_reservation_lock); /* * ext4_calc_metadata_amount() has side effects, which we have @@ -1297,10 +1289,6 @@ repeat: ei->i_da_metadata_calc_len = save_len; ei->i_da_metadata_calc_last_lblock = save_last_lblock; spin_unlock(&ei->i_block_reservation_lock); - if (ext4_should_retry_alloc(inode->i_sb, &retries)) { - cond_resched(); - goto repeat; - } dquot_release_reservation_block(inode, EXT4_C2B(sbi, 1)); return -ENOSPC; } -- 2.7.4