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| author | Chandan Rajendra <chandan@linux.vnet.ibm.com> | 2016-12-23 15:00:18 +0530 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-07-05 14:40:22 +0200 |
| commit | e8b5068b64d0505fe138e3db243e6e3385ae1a15 (patch) | |
| tree | 4f3af06118c45a34413b93a40b540cb5399278cb /drivers/fpga/zynq-fpga.c | |
| parent | 83571e9ef7c91ef6e249aae374de068b30963551 (diff) | |
Btrfs: Fix deadlock between direct IO and fast fsync
[ Upstream commit 97dcdea076ecef41ea4aaa23d4397c2f622e4265 ]
The following deadlock is seen when executing generic/113 test,
---------------------------------------------------------+----------------------------------------------------
Direct I/O task Fast fsync task
---------------------------------------------------------+----------------------------------------------------
btrfs_direct_IO
__blockdev_direct_IO
do_blockdev_direct_IO
do_direct_IO
btrfs_get_blocks_direct
while (blocks needs to written)
get_more_blocks (first iteration)
btrfs_get_blocks_direct
btrfs_create_dio_extent
down_read(&BTRFS_I(inode) >dio_sem)
Create and add extent map and ordered extent
up_read(&BTRFS_I(inode) >dio_sem)
btrfs_sync_file
btrfs_log_dentry_safe
btrfs_log_inode_parent
btrfs_log_inode
btrfs_log_changed_extents
down_write(&BTRFS_I(inode) >dio_sem)
Collect new extent maps and ordered extents
wait for ordered extent completion
get_more_blocks (second iteration)
btrfs_get_blocks_direct
btrfs_create_dio_extent
down_read(&BTRFS_I(inode) >dio_sem)
--------------------------------------------------------------------------------------------------------------
In the above description, Btrfs direct I/O code path has not yet started
submitting bios for file range covered by the initial ordered
extent. Meanwhile, The fast fsync task obtains the write semaphore and
waits for I/O on the ordered extent to get completed. However, the
Direct I/O task is now blocked on obtaining the read semaphore.
To resolve the deadlock, this commit modifies the Direct I/O code path
to obtain the read semaphore before invoking
__blockdev_direct_IO(). The semaphore is then given up after
__blockdev_direct_IO() returns. This allows the Direct I/O code to
complete I/O on all the ordered extents it creates.
Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/fpga/zynq-fpga.c')
0 files changed, 0 insertions, 0 deletions