From: John Groves <[email protected]> This commit introduces fs/famfs/famfs_file.c and the famfs file_operations for read/write.
This is not usable yet because: * It calls dax_iomap_rw() with NULL iomap_ops (which will be introduced in a subsequent commit). * famfs_ioctl() is coming in a later commit, and it is necessary to map a file to a memory allocation. Signed-off-by: John Groves <[email protected]> --- v13: - Use copy_splice_read() instead of filemap_splice_read() for .splice_read: famfs inodes are DAX (no page cache), so filemap_splice_read() faulted in zero-filled ram_aops folios and splice()/sendfile() returned a stream of zeroes; copy_splice_read() routes through ->read_iter (dax_iomap_rw) and returns the real data (Sashiko bot). - No code change. The Sashiko bot flagged that famfs_dax_write_iter() does not call generic_write_sync() for O_SYNC/O_DSYNC writes. Considered and declined -- the finding does not apply to famfs: there is no page cache, no dirty tracking and no writeback, and ->fsync is noop_fsync by design, so generic_write_sync() resolves to vfs_fsync_range() -> noop_fsync() -> 0, an inert no-op. Bla bla bla ;) fs/famfs/Makefile | 2 +- fs/famfs/famfs_file.c | 141 ++++++++++++++++++++++++++++++++++++++ fs/famfs/famfs_inode.c | 2 +- fs/famfs/famfs_internal.h | 2 + 4 files changed, 145 insertions(+), 2 deletions(-) create mode 100644 fs/famfs/famfs_file.c diff --git a/fs/famfs/Makefile b/fs/famfs/Makefile index 62230bcd6793..8cac90c090a4 100644 --- a/fs/famfs/Makefile +++ b/fs/famfs/Makefile @@ -2,4 +2,4 @@ obj-$(CONFIG_FAMFS) += famfs.o -famfs-y := famfs_inode.o +famfs-y := famfs_inode.o famfs_file.o diff --git a/fs/famfs/famfs_file.c b/fs/famfs/famfs_file.c new file mode 100644 index 000000000000..1369fe1824bc --- /dev/null +++ b/fs/famfs/famfs_file.c @@ -0,0 +1,141 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * famfs - dax file system for shared fabric-attached memory + * + * Copyright 2023-2024 Micron Technology, Inc. + * + * This file system, originally based on ramfs the dax support from xfs, + * is intended to allow multiple host systems to mount a common file system + * view of dax files that map to shared memory. + */ + +#include <linux/fs.h> +#include <linux/mm.h> +#include <linux/dax.h> +#include <linux/iomap.h> + +#include "famfs_internal.h" + +/********************************************************************* + * file_operations + */ + +/* Reject I/O to files that aren't in a valid state */ +static ssize_t +famfs_file_invalid(struct inode *inode) +{ + if (!IS_DAX(inode)) { + pr_debug("%s: inode %llx IS_DAX is false\n", + __func__, (u64)inode); + return -ENXIO; + } + return 0; +} + +static ssize_t +famfs_rw_prep(struct kiocb *iocb, struct iov_iter *ubuf) +{ + struct inode *inode = iocb->ki_filp->f_mapping->host; + struct super_block *sb = inode->i_sb; + struct famfs_fs_info *fsi = sb->s_fs_info; + size_t i_size = i_size_read(inode); + size_t count = iov_iter_count(ubuf); + size_t max_count; + ssize_t rc; + + if (fsi->deverror) + return -ENODEV; + + rc = famfs_file_invalid(inode); + if (rc) + return rc; + + /* Avoid unsigned underflow if position is past EOF */ + if (iocb->ki_pos >= i_size) + max_count = 0; + else + max_count = i_size - iocb->ki_pos; + + if (count > max_count) + iov_iter_truncate(ubuf, max_count); + + if (!iov_iter_count(ubuf)) + return 0; + + return rc; +} + +static ssize_t +famfs_dax_read_iter(struct kiocb *iocb, struct iov_iter *to) +{ + struct inode *inode = iocb->ki_filp->f_mapping->host; + ssize_t rc; + + /* dax_iomap_rw() requires i_rwsem held (shared for read) */ + inode_lock_shared(inode); + rc = famfs_rw_prep(iocb, to); + if (rc || !iov_iter_count(to)) { + inode_unlock_shared(inode); + return rc; + } + + rc = dax_iomap_rw(iocb, to, NULL /*&famfs_iomap_ops */); + inode_unlock_shared(inode); + + if (rc > 0) + file_accessed(iocb->ki_filp); + return rc; +} + +/** + * famfs_dax_write_iter() + * + * We need our own write-iter in order to prevent append + * + * @iocb: + * @from: iterator describing the user memory source for the write + */ +static ssize_t +famfs_dax_write_iter(struct kiocb *iocb, struct iov_iter *from) +{ + struct inode *inode = iocb->ki_filp->f_mapping->host; + struct famfs_fs_info *fsi = inode->i_sb->s_fs_info; + ssize_t rc; + + if (!famfs_opt_enabled(fsi, FAMFS_OPT_WRITE)) + return -EPERM; + + /* dax_iomap_rw() requires i_rwsem held (exclusive for write) */ + inode_lock(inode); + rc = famfs_rw_prep(iocb, from); + if (rc || !iov_iter_count(from)) { + inode_unlock(inode); + return rc; + } + + kiocb_modified(iocb); /* mtime/ctime + strip set[e]uid */ + + rc = dax_iomap_rw(iocb, from, NULL /*&famfs_iomap_ops*/); + inode_unlock(inode); + return rc; +} + +const struct file_operations famfs_file_operations = { + .owner = THIS_MODULE, + + /* Custom famfs operations */ + .write_iter = famfs_dax_write_iter, + .read_iter = famfs_dax_read_iter, + .unlocked_ioctl = NULL /*famfs_file_ioctl*/, + .mmap = NULL /* famfs_file_mmap */, + + /* Force PMD alignment for mmap */ + .get_unmapped_area = thp_get_unmapped_area, + + /* Generic Operations */ + .fsync = noop_fsync, + .splice_read = copy_splice_read, + .splice_write = iter_file_splice_write, + .llseek = generic_file_llseek, +}; + diff --git a/fs/famfs/famfs_inode.c b/fs/famfs/famfs_inode.c index b7a3d8d6ee8c..9e8662c4ac98 100644 --- a/fs/famfs/famfs_inode.c +++ b/fs/famfs/famfs_inode.c @@ -59,7 +59,7 @@ famfs_get_inode( break; case S_IFREG: inode->i_op = &famfs_file_inode_operations; - inode->i_fop = NULL /* &famfs_file_operations */; + inode->i_fop = &famfs_file_operations; break; case S_IFDIR: inode->i_op = &famfs_dir_inode_operations; diff --git a/fs/famfs/famfs_internal.h b/fs/famfs/famfs_internal.h index 30f0b01010d5..ff9f1d3f686e 100644 --- a/fs/famfs/famfs_internal.h +++ b/fs/famfs/famfs_internal.h @@ -15,6 +15,8 @@ #include <linux/bits.h> #include <linux/build_bug.h> +extern const struct file_operations famfs_file_operations; + struct famfs_mount_opts { umode_t mode; }; -- 2.53.0
