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[114.78.127.22]) by smtp.gmail.com with ESMTPSA id x190sm11771535pfc.89.2019.10.28.03.52.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Oct 2019 03:52:43 -0700 (PDT) Date: Mon, 28 Oct 2019 21:52:37 +1100 From: Matthew Bobrowski To: tytso@mit.edu, jack@suse.cz, adilger.kernel@dilger.ca Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, hch@infradead.org, david@fromorbit.com, darrick.wong@oracle.com Subject: [PATCH v6 07/11] ext4: introduce direct I/O read using iomap infrastructure Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org This patch introduces a new direct I/O read path which makes use of the iomap infrastructure. The new function ext4_do_read_iter() is responsible for calling into the iomap infrastructure via iomap_dio_rw(). If the read operation performed on the inode is not supported, which is checked via ext4_dio_supported(), then we simply fallback and complete the I/O using buffered I/O. Existing direct I/O read code path has been removed, as it is now redundant. Signed-off-by: Matthew Bobrowski Reviewed-by: Jan Kara Reviewed-by: Ritesh Harjani --- fs/ext4/file.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++-- fs/ext4/inode.c | 38 +--------------------------------- 2 files changed, 54 insertions(+), 39 deletions(-) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index ab75aee3e687..440f4c6ba4ee 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -34,6 +34,52 @@ #include "xattr.h" #include "acl.h" +static bool ext4_dio_supported(struct inode *inode) +{ + if (IS_ENABLED(CONFIG_FS_ENCRYPTION) && IS_ENCRYPTED(inode)) + return false; + if (fsverity_active(inode)) + return false; + if (ext4_should_journal_data(inode)) + return false; + if (ext4_has_inline_data(inode)) + return false; + return true; +} + +static ssize_t ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to) +{ + ssize_t ret; + struct inode *inode = file_inode(iocb->ki_filp); + + if (iocb->ki_flags & IOCB_NOWAIT) { + if (!inode_trylock_shared(inode)) + return -EAGAIN; + } else { + inode_lock_shared(inode); + } + + if (!ext4_dio_supported(inode)) { + inode_unlock_shared(inode); + /* + * Fallback to buffered I/O if the operation being performed on + * the inode is not supported by direct I/O. The IOCB_DIRECT + * flag needs to be cleared here in order to ensure that the + * direct I/O path within generic_file_read_iter() is not + * taken. + */ + iocb->ki_flags &= ~IOCB_DIRECT; + return generic_file_read_iter(iocb, to); + } + + ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, + is_sync_kiocb(iocb)); + inode_unlock_shared(inode); + + file_accessed(iocb->ki_filp); + return ret; +} + #ifdef CONFIG_FS_DAX static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to) { @@ -64,16 +110,21 @@ static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to) static ssize_t ext4_file_read_iter(struct kiocb *iocb, struct iov_iter *to) { - if (unlikely(ext4_forced_shutdown(EXT4_SB(file_inode(iocb->ki_filp)->i_sb)))) + struct inode *inode = file_inode(iocb->ki_filp); + + if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb)))) return -EIO; if (!iov_iter_count(to)) return 0; /* skip atime */ #ifdef CONFIG_FS_DAX - if (IS_DAX(file_inode(iocb->ki_filp))) + if (IS_DAX(inode)) return ext4_dax_read_iter(iocb, to); #endif + if (iocb->ki_flags & IOCB_DIRECT) + return ext4_dio_read_iter(iocb, to); + return generic_file_read_iter(iocb, to); } diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 50b4835cd927..e44b3b1dbbc4 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -863,9 +863,6 @@ int ext4_dio_get_block(struct inode *inode, sector_t iblock, { /* We don't expect handle for direct IO */ WARN_ON_ONCE(ext4_journal_current_handle()); - - if (!create) - return _ext4_get_block(inode, iblock, bh, 0); return ext4_get_block_trans(inode, iblock, bh, EXT4_GET_BLOCKS_CREATE); } @@ -3874,36 +3871,6 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter) return ret; } -static ssize_t ext4_direct_IO_read(struct kiocb *iocb, struct iov_iter *iter) -{ - struct address_space *mapping = iocb->ki_filp->f_mapping; - struct inode *inode = mapping->host; - size_t count = iov_iter_count(iter); - ssize_t ret; - - /* - * Shared inode_lock is enough for us - it protects against concurrent - * writes & truncates and since we take care of writing back page cache, - * we are protected against page writeback as well. - */ - if (iocb->ki_flags & IOCB_NOWAIT) { - if (!inode_trylock_shared(inode)) - return -EAGAIN; - } else { - inode_lock_shared(inode); - } - - ret = filemap_write_and_wait_range(mapping, iocb->ki_pos, - iocb->ki_pos + count - 1); - if (ret) - goto out_unlock; - ret = __blockdev_direct_IO(iocb, inode, inode->i_sb->s_bdev, - iter, ext4_dio_get_block, NULL, NULL, 0); -out_unlock: - inode_unlock_shared(inode); - return ret; -} - static ssize_t ext4_direct_IO(struct kiocb *iocb, struct iov_iter *iter) { struct file *file = iocb->ki_filp; @@ -3930,10 +3897,7 @@ static ssize_t ext4_direct_IO(struct kiocb *iocb, struct iov_iter *iter) return 0; trace_ext4_direct_IO_enter(inode, offset, count, iov_iter_rw(iter)); - if (iov_iter_rw(iter) == READ) - ret = ext4_direct_IO_read(iocb, iter); - else - ret = ext4_direct_IO_write(iocb, iter); + ret = ext4_direct_IO_write(iocb, iter); trace_ext4_direct_IO_exit(inode, offset, count, iov_iter_rw(iter), ret); return ret; }