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Diffstat (limited to 'fs/ceph/io.c')
| -rw-r--r-- | fs/ceph/io.c | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/fs/ceph/io.c b/fs/ceph/io.c new file mode 100644 index 0000000000..c456509b31 --- /dev/null +++ b/fs/ceph/io.c @@ -0,0 +1,163 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (c) 2016 Trond Myklebust + * Copyright (c) 2019 Jeff Layton + * + * I/O and data path helper functionality. + * + * Heavily borrowed from equivalent code in fs/nfs/io.c + */ + +#include <linux/ceph/ceph_debug.h> + +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/rwsem.h> +#include <linux/fs.h> + +#include "super.h" +#include "io.h" + +/* Call with exclusively locked inode->i_rwsem */ +static void ceph_block_o_direct(struct ceph_inode_info *ci, struct inode *inode) +{ + lockdep_assert_held_write(&inode->i_rwsem); + + if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT) { + spin_lock(&ci->i_ceph_lock); + ci->i_ceph_flags &= ~CEPH_I_ODIRECT; + spin_unlock(&ci->i_ceph_lock); + inode_dio_wait(inode); + } +} + +/** + * ceph_start_io_read - declare the file is being used for buffered reads + * @inode: file inode + * + * Declare that a buffered read operation is about to start, and ensure + * that we block all direct I/O. + * On exit, the function ensures that the CEPH_I_ODIRECT flag is unset, + * and holds a shared lock on inode->i_rwsem to ensure that the flag + * cannot be changed. + * In practice, this means that buffered read operations are allowed to + * execute in parallel, thanks to the shared lock, whereas direct I/O + * operations need to wait to grab an exclusive lock in order to set + * CEPH_I_ODIRECT. + * Note that buffered writes and truncates both take a write lock on + * inode->i_rwsem, meaning that those are serialised w.r.t. the reads. + */ +void +ceph_start_io_read(struct inode *inode) +{ + struct ceph_inode_info *ci = ceph_inode(inode); + + /* Be an optimist! */ + down_read(&inode->i_rwsem); + if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)) + return; + up_read(&inode->i_rwsem); + /* Slow path.... */ + down_write(&inode->i_rwsem); + ceph_block_o_direct(ci, inode); + downgrade_write(&inode->i_rwsem); +} + +/** + * ceph_end_io_read - declare that the buffered read operation is done + * @inode: file inode + * + * Declare that a buffered read operation is done, and release the shared + * lock on inode->i_rwsem. + */ +void +ceph_end_io_read(struct inode *inode) +{ + up_read(&inode->i_rwsem); +} + +/** + * ceph_start_io_write - declare the file is being used for buffered writes + * @inode: file inode + * + * Declare that a buffered write operation is about to start, and ensure + * that we block all direct I/O. + */ +void +ceph_start_io_write(struct inode *inode) +{ + down_write(&inode->i_rwsem); + ceph_block_o_direct(ceph_inode(inode), inode); +} + +/** + * ceph_end_io_write - declare that the buffered write operation is done + * @inode: file inode + * + * Declare that a buffered write operation is done, and release the + * lock on inode->i_rwsem. + */ +void +ceph_end_io_write(struct inode *inode) +{ + up_write(&inode->i_rwsem); +} + +/* Call with exclusively locked inode->i_rwsem */ +static void ceph_block_buffered(struct ceph_inode_info *ci, struct inode *inode) +{ + lockdep_assert_held_write(&inode->i_rwsem); + + if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)) { + spin_lock(&ci->i_ceph_lock); + ci->i_ceph_flags |= CEPH_I_ODIRECT; + spin_unlock(&ci->i_ceph_lock); + /* FIXME: unmap_mapping_range? */ + filemap_write_and_wait(inode->i_mapping); + } +} + +/** + * ceph_start_io_direct - declare the file is being used for direct i/o + * @inode: file inode + * + * Declare that a direct I/O operation is about to start, and ensure + * that we block all buffered I/O. + * On exit, the function ensures that the CEPH_I_ODIRECT flag is set, + * and holds a shared lock on inode->i_rwsem to ensure that the flag + * cannot be changed. + * In practice, this means that direct I/O operations are allowed to + * execute in parallel, thanks to the shared lock, whereas buffered I/O + * operations need to wait to grab an exclusive lock in order to clear + * CEPH_I_ODIRECT. + * Note that buffered writes and truncates both take a write lock on + * inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT. + */ +void +ceph_start_io_direct(struct inode *inode) +{ + struct ceph_inode_info *ci = ceph_inode(inode); + + /* Be an optimist! */ + down_read(&inode->i_rwsem); + if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT) + return; + up_read(&inode->i_rwsem); + /* Slow path.... */ + down_write(&inode->i_rwsem); + ceph_block_buffered(ci, inode); + downgrade_write(&inode->i_rwsem); +} + +/** + * ceph_end_io_direct - declare that the direct i/o operation is done + * @inode: file inode + * + * Declare that a direct I/O operation is done, and release the shared + * lock on inode->i_rwsem. + */ +void +ceph_end_io_direct(struct inode *inode) +{ + up_read(&inode->i_rwsem); +} |