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 <a-fujita@rs.jp.nec.com> Reviewed-by: Zheng Liu <wenqing.lz@taobao.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: stable@vger.kernel.org
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@ -1206,7 +1206,6 @@ static int ext4_journalled_write_end(struct file *file,
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*/
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static int ext4_da_reserve_metadata(struct inode *inode, ext4_lblk_t lblock)
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{
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int retries = 0;
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struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
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struct ext4_inode_info *ei = EXT4_I(inode);
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unsigned int md_needed;
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@ -1218,7 +1217,6 @@ static int ext4_da_reserve_metadata(struct inode *inode, ext4_lblk_t lblock)
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* in order to allocate nrblocks
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* worse case is one extent per block
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*/
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repeat:
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spin_lock(&ei->i_block_reservation_lock);
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/*
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* ext4_calc_metadata_amount() has side effects, which we have
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@ -1238,10 +1236,6 @@ static int ext4_da_reserve_metadata(struct inode *inode, ext4_lblk_t lblock)
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ei->i_da_metadata_calc_len = save_len;
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ei->i_da_metadata_calc_last_lblock = save_last_lblock;
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spin_unlock(&ei->i_block_reservation_lock);
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if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
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cond_resched();
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goto repeat;
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}
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return -ENOSPC;
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}
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ei->i_reserved_meta_blocks += md_needed;
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@ -1255,7 +1249,6 @@ static int ext4_da_reserve_metadata(struct inode *inode, ext4_lblk_t lblock)
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*/
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static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock)
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{
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int retries = 0;
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struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
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struct ext4_inode_info *ei = EXT4_I(inode);
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unsigned int md_needed;
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@ -1277,7 +1270,6 @@ static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock)
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* in order to allocate nrblocks
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* worse case is one extent per block
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*/
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repeat:
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spin_lock(&ei->i_block_reservation_lock);
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/*
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* ext4_calc_metadata_amount() has side effects, which we have
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@ -1297,10 +1289,6 @@ static int ext4_da_reserve_space(struct inode *inode, ext4_lblk_t lblock)
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ei->i_da_metadata_calc_len = save_len;
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ei->i_da_metadata_calc_last_lblock = save_last_lblock;
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spin_unlock(&ei->i_block_reservation_lock);
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if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
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cond_resched();
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goto repeat;
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}
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dquot_release_reservation_block(inode, EXT4_C2B(sbi, 1));
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return -ENOSPC;
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}
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