forked from Minki/linux
Btrfs: Direct I/O: Fix space accounting
The following call trace is seen when generic/095 test is executed, WARNING: CPU: 3 PID: 2769 at /home/chandan/code/repos/linux/fs/btrfs/inode.c:8967 btrfs_destroy_inode+0x284/0x2a0() Modules linked in: CPU: 3 PID: 2769 Comm: umount Not tainted 4.2.0-rc5+ #31 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20150306_163512-brownie 04/01/2014 ffffffff81c08150 ffff8802ec9cbce8 ffffffff81984058 ffff8802ffd8feb0 0000000000000000 ffff8802ec9cbd28 ffffffff81050385 ffff8802ec9cbd38 ffff8802d12f8588 ffff8802d12f8588 ffff8802f15ab000 ffff8800bb96c0b0 Call Trace: [<ffffffff81984058>] dump_stack+0x45/0x57 [<ffffffff81050385>] warn_slowpath_common+0x85/0xc0 [<ffffffff81050465>] warn_slowpath_null+0x15/0x20 [<ffffffff81340294>] btrfs_destroy_inode+0x284/0x2a0 [<ffffffff8117ce07>] destroy_inode+0x37/0x60 [<ffffffff8117cf39>] evict+0x109/0x170 [<ffffffff8117cfd5>] dispose_list+0x35/0x50 [<ffffffff8117dd3a>] evict_inodes+0xaa/0x100 [<ffffffff81165667>] generic_shutdown_super+0x47/0xf0 [<ffffffff81165951>] kill_anon_super+0x11/0x20 [<ffffffff81302093>] btrfs_kill_super+0x13/0x110 [<ffffffff81165c99>] deactivate_locked_super+0x39/0x70 [<ffffffff811660cf>] deactivate_super+0x5f/0x70 [<ffffffff81180e1e>] cleanup_mnt+0x3e/0x90 [<ffffffff81180ebd>] __cleanup_mnt+0xd/0x10 [<ffffffff81069c06>] task_work_run+0x96/0xb0 [<ffffffff81003a3d>] do_notify_resume+0x3d/0x50 [<ffffffff8198cbc2>] int_signal+0x12/0x17 This means that the inode had non-zero "outstanding extents" during eviction. This occurs because, during direct I/O a task which successfully used up its reserved data space would set BTRFS_INODE_DIO_READY bit and does not clear the bit after finishing the DIO write. A future DIO write could actually fail and the unused reserve space won't be freed because of the previously set BTRFS_INODE_DIO_READY bit. Clearing the BTRFS_INODE_DIO_READY bit in btrfs_direct_IO() caused the following issue, |-----------------------------------+-------------------------------------| | Task A | Task B | |-----------------------------------+-------------------------------------| | Start direct i/o write on inode X.| | | reserve space | | | Allocate ordered extent | | | release reserved space | | | Set BTRFS_INODE_DIO_READY bit. | | | | splice() | | | Transfer data from pipe buffer to | | | destination file. | | | - kmap(pipe buffer page) | | | - Start direct i/o write on | | | inode X. | | | - reserve space | | | - dio_refill_pages() | | | - sdio->blocks_available == 0 | | | - Since a kernel address is | | | being passed instead of a | | | user space address, | | | iov_iter_get_pages() returns | | | -EFAULT. | | | - Since BTRFS_INODE_DIO_READY is | | | set, we don't release reserved | | | space. | | | - Clear BTRFS_INODE_DIO_READY bit.| | -EIOCBQUEUED is returned. | | |-----------------------------------+-------------------------------------| Hence this commit introduces "struct btrfs_dio_data" to track the usage of reserved data space. The remaining unused "reserve space" can now be freed reliably. Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com> Reviewed-by: Liu Bo <bo.li.liu@oracle.com> Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
chandan
Chris Mason
parent
a30e577c96
commit
50745b0a7f
@ -44,8 +44,6 @@
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#define BTRFS_INODE_IN_DELALLOC_LIST 9
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#define BTRFS_INODE_READDIO_NEED_LOCK 10
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#define BTRFS_INODE_HAS_PROPS 11
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/* DIO is ready to submit */
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#define BTRFS_INODE_DIO_READY 12
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/*
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* The following 3 bits are meant only for the btree inode.
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* When any of them is set, it means an error happened while writing an
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@ -7405,6 +7405,10 @@ static struct extent_map *create_pinned_em(struct inode *inode, u64 start,
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return em;
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}
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struct btrfs_dio_data {
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u64 outstanding_extents;
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u64 reserve;
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};
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static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
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struct buffer_head *bh_result, int create)
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@ -7412,10 +7416,10 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
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struct extent_map *em;
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struct btrfs_root *root = BTRFS_I(inode)->root;
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struct extent_state *cached_state = NULL;
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struct btrfs_dio_data *dio_data = NULL;
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u64 start = iblock << inode->i_blkbits;
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u64 lockstart, lockend;
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u64 len = bh_result->b_size;
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u64 *outstanding_extents = NULL;
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int unlock_bits = EXTENT_LOCKED;
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int ret = 0;
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@ -7433,7 +7437,7 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
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* that anything that needs to check if there's a transction doesn't get
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* confused.
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*/
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outstanding_extents = current->journal_info;
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dio_data = current->journal_info;
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current->journal_info = NULL;
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}
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@ -7565,17 +7569,18 @@ unlock:
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* within our reservation, otherwise we need to adjust our inode
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* counter appropriately.
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*/
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if (*outstanding_extents) {
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(*outstanding_extents)--;
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if (dio_data->outstanding_extents) {
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(dio_data->outstanding_extents)--;
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} else {
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spin_lock(&BTRFS_I(inode)->lock);
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BTRFS_I(inode)->outstanding_extents++;
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spin_unlock(&BTRFS_I(inode)->lock);
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}
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current->journal_info = outstanding_extents;
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btrfs_free_reserved_data_space(inode, len);
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set_bit(BTRFS_INODE_DIO_READY, &BTRFS_I(inode)->runtime_flags);
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WARN_ON(dio_data->reserve < len);
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dio_data->reserve -= len;
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current->journal_info = dio_data;
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}
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/*
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@ -7598,8 +7603,8 @@ unlock:
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unlock_err:
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clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart, lockend,
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unlock_bits, 1, 0, &cached_state, GFP_NOFS);
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if (outstanding_extents)
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current->journal_info = outstanding_extents;
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if (dio_data)
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current->journal_info = dio_data;
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return ret;
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}
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@ -8329,7 +8334,8 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
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{
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struct file *file = iocb->ki_filp;
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struct inode *inode = file->f_mapping->host;
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u64 outstanding_extents = 0;
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struct btrfs_root *root = BTRFS_I(inode)->root;
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struct btrfs_dio_data dio_data = { 0 };
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size_t count = 0;
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int flags = 0;
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bool wakeup = true;
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@ -8367,7 +8373,7 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
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ret = btrfs_delalloc_reserve_space(inode, count);
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if (ret)
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goto out;
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outstanding_extents = div64_u64(count +
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dio_data.outstanding_extents = div64_u64(count +
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BTRFS_MAX_EXTENT_SIZE - 1,
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BTRFS_MAX_EXTENT_SIZE);
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@ -8376,7 +8382,8 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
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* do the accounting properly if we go over the number we
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* originally calculated. Abuse current->journal_info for this.
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*/
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current->journal_info = &outstanding_extents;
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dio_data.reserve = round_up(count, root->sectorsize);
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current->journal_info = &dio_data;
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} else if (test_bit(BTRFS_INODE_READDIO_NEED_LOCK,
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&BTRFS_I(inode)->runtime_flags)) {
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inode_dio_end(inode);
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@ -8391,16 +8398,9 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
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if (iov_iter_rw(iter) == WRITE) {
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current->journal_info = NULL;
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if (ret < 0 && ret != -EIOCBQUEUED) {
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/*
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* If the error comes from submitting stage,
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* btrfs_get_blocsk_direct() has free'd data space,
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* and metadata space will be handled by
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* finish_ordered_fn, don't do that again to make
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* sure bytes_may_use is correct.
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*/
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if (!test_and_clear_bit(BTRFS_INODE_DIO_READY,
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&BTRFS_I(inode)->runtime_flags))
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btrfs_delalloc_release_space(inode, count);
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if (dio_data.reserve)
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btrfs_delalloc_release_space(inode,
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dio_data.reserve);
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} else if (ret >= 0 && (size_t)ret < count)
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btrfs_delalloc_release_space(inode,
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count - (size_t)ret);
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