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1// SPDX-License-Identifier: GPL-2.02/*3 * Copyright (c) 2016 Trond Myklebust4 * Copyright (c) 2019 Jeff Layton5 *6 * I/O and data path helper functionality.7 *8 * Heavily borrowed from equivalent code in fs/nfs/io.c9 */10 11#include <linux/ceph/ceph_debug.h>12 13#include <linux/types.h>14#include <linux/kernel.h>15#include <linux/rwsem.h>16#include <linux/fs.h>17 18#include "super.h"19#include "io.h"20 21/* Call with exclusively locked inode->i_rwsem */22static void ceph_block_o_direct(struct ceph_inode_info *ci, struct inode *inode)23{24 lockdep_assert_held_write(&inode->i_rwsem);25 26 if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT) {27 spin_lock(&ci->i_ceph_lock);28 ci->i_ceph_flags &= ~CEPH_I_ODIRECT;29 spin_unlock(&ci->i_ceph_lock);30 inode_dio_wait(inode);31 }32}33 34/**35 * ceph_start_io_read - declare the file is being used for buffered reads36 * @inode: file inode37 *38 * Declare that a buffered read operation is about to start, and ensure39 * that we block all direct I/O.40 * On exit, the function ensures that the CEPH_I_ODIRECT flag is unset,41 * and holds a shared lock on inode->i_rwsem to ensure that the flag42 * cannot be changed.43 * In practice, this means that buffered read operations are allowed to44 * execute in parallel, thanks to the shared lock, whereas direct I/O45 * operations need to wait to grab an exclusive lock in order to set46 * CEPH_I_ODIRECT.47 * Note that buffered writes and truncates both take a write lock on48 * inode->i_rwsem, meaning that those are serialised w.r.t. the reads.49 */50void51ceph_start_io_read(struct inode *inode)52{53 struct ceph_inode_info *ci = ceph_inode(inode);54 55 /* Be an optimist! */56 down_read(&inode->i_rwsem);57 if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT))58 return;59 up_read(&inode->i_rwsem);60 /* Slow path.... */61 down_write(&inode->i_rwsem);62 ceph_block_o_direct(ci, inode);63 downgrade_write(&inode->i_rwsem);64}65 66/**67 * ceph_end_io_read - declare that the buffered read operation is done68 * @inode: file inode69 *70 * Declare that a buffered read operation is done, and release the shared71 * lock on inode->i_rwsem.72 */73void74ceph_end_io_read(struct inode *inode)75{76 up_read(&inode->i_rwsem);77}78 79/**80 * ceph_start_io_write - declare the file is being used for buffered writes81 * @inode: file inode82 *83 * Declare that a buffered write operation is about to start, and ensure84 * that we block all direct I/O.85 */86void87ceph_start_io_write(struct inode *inode)88{89 down_write(&inode->i_rwsem);90 ceph_block_o_direct(ceph_inode(inode), inode);91}92 93/**94 * ceph_end_io_write - declare that the buffered write operation is done95 * @inode: file inode96 *97 * Declare that a buffered write operation is done, and release the98 * lock on inode->i_rwsem.99 */100void101ceph_end_io_write(struct inode *inode)102{103 up_write(&inode->i_rwsem);104}105 106/* Call with exclusively locked inode->i_rwsem */107static void ceph_block_buffered(struct ceph_inode_info *ci, struct inode *inode)108{109 lockdep_assert_held_write(&inode->i_rwsem);110 111 if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)) {112 spin_lock(&ci->i_ceph_lock);113 ci->i_ceph_flags |= CEPH_I_ODIRECT;114 spin_unlock(&ci->i_ceph_lock);115 /* FIXME: unmap_mapping_range? */116 filemap_write_and_wait(inode->i_mapping);117 }118}119 120/**121 * ceph_start_io_direct - declare the file is being used for direct i/o122 * @inode: file inode123 *124 * Declare that a direct I/O operation is about to start, and ensure125 * that we block all buffered I/O.126 * On exit, the function ensures that the CEPH_I_ODIRECT flag is set,127 * and holds a shared lock on inode->i_rwsem to ensure that the flag128 * cannot be changed.129 * In practice, this means that direct I/O operations are allowed to130 * execute in parallel, thanks to the shared lock, whereas buffered I/O131 * operations need to wait to grab an exclusive lock in order to clear132 * CEPH_I_ODIRECT.133 * Note that buffered writes and truncates both take a write lock on134 * inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT.135 */136void137ceph_start_io_direct(struct inode *inode)138{139 struct ceph_inode_info *ci = ceph_inode(inode);140 141 /* Be an optimist! */142 down_read(&inode->i_rwsem);143 if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)144 return;145 up_read(&inode->i_rwsem);146 /* Slow path.... */147 down_write(&inode->i_rwsem);148 ceph_block_buffered(ci, inode);149 downgrade_write(&inode->i_rwsem);150}151 152/**153 * ceph_end_io_direct - declare that the direct i/o operation is done154 * @inode: file inode155 *156 * Declare that a direct I/O operation is done, and release the shared157 * lock on inode->i_rwsem.158 */159void160ceph_end_io_direct(struct inode *inode)161{162 up_read(&inode->i_rwsem);163}164