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