// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/ext4/file.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/file.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  ext4 fs regular file handling primitives
 *
 *  64-bit file support on 64-bit platforms by Jakub Jelinek
 *      (jj@sunsite.ms.mff.cuni.cz)
 */

#include <linux/time.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/path.h>
#include <linux/dax.h>
#include <linux/quotaops.h>
#include <linux/pagevec.h>
#include <linux/uio.h>
#include "ext4.h"
#include "ext4_jbd2.h"
#include "xattr.h"
#include "acl.h"

#ifdef CONFIG_FS_DAX
static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
        struct inode *inode = file_inode(iocb->ki_filp);
        ssize_t ret;

        if (!inode_trylock_shared(inode)) {
                if (iocb->ki_flags & IOCB_NOWAIT)
                        return -EAGAIN;
                inode_lock_shared(inode);
        }
        /*
         * Recheck under inode lock - at this point we are sure it cannot
         * change anymore
         */
        if (!IS_DAX(inode)) {
                inode_unlock_shared(inode);
                /* Fallback to buffered IO in case we cannot support DAX */
                return generic_file_read_iter(iocb, to);
        }
        ret = dax_iomap_rw(iocb, to, &ext4_iomap_ops);
        inode_unlock_shared(inode);

        file_accessed(iocb->ki_filp);
        return ret;
}
#endif

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))))
                return -EIO;

        if (!iov_iter_count(to))
                return 0; /* skip atime */

#ifdef CONFIG_FS_DAX
        if (IS_DAX(file_inode(iocb->ki_filp)))
                return ext4_dax_read_iter(iocb, to);
#endif
        return generic_file_read_iter(iocb, to);
}

/*
 * Called when an inode is released. Note that this is different
 * from ext4_file_open: open gets called at every open, but release
 * gets called only when /all/ the files are closed.
 */
static int ext4_release_file(struct inode *inode, struct file *filp)
{
        if (ext4_test_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE)) {
                ext4_alloc_da_blocks(inode);
                ext4_clear_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
        }
        /* if we are the last writer on the inode, drop the block reservation */
        if ((filp->f_mode & FMODE_WRITE) &&
                        (atomic_read(&inode->i_writecount) == 1) &&
                        !EXT4_I(inode)->i_reserved_data_blocks)
        {
                down_write(&EXT4_I(inode)->i_data_sem);
                ext4_discard_preallocations(inode);
                up_write(&EXT4_I(inode)->i_data_sem);
        }
        if (is_dx(inode) && filp->private_data)
                ext4_htree_free_dir_info(filp->private_data);

        return 0;
}

static void ext4_unwritten_wait(struct inode *inode)
{
        wait_queue_head_t *wq = ext4_ioend_wq(inode);

        wait_event(*wq, (atomic_read(&EXT4_I(inode)->i_unwritten) == 0));
}

/*
 * This tests whether the IO in question is block-aligned or not.
 * Ext4 utilizes unwritten extents when hole-filling during direct IO, and they
 * are converted to written only after the IO is complete.  Until they are
 * mapped, these blocks appear as holes, so dio_zero_block() will assume that
 * it needs to zero out portions of the start and/or end block.  If 2 AIO
 * threads are at work on the same unwritten block, they must be synchronized
 * or one thread will zero the other's data, causing corruption.
 */
static int
ext4_unaligned_aio(struct inode *inode, struct iov_iter *from, loff_t pos)
{
        struct super_block *sb = inode->i_sb;
        int blockmask = sb->s_blocksize - 1;

        if (pos >= i_size_read(inode))
                return 0;

        if ((pos | iov_iter_alignment(from)) & blockmask)
                return 1;

        return 0;
}

/* Is IO overwriting allocated and initialized blocks? */
static bool ext4_overwrite_io(struct inode *inode, loff_t pos, loff_t len)
{
        struct ext4_map_blocks map;
        unsigned int blkbits = inode->i_blkbits;
        int err, blklen;

        if (pos + len > i_size_read(inode))
                return false;

        map.m_lblk = pos >> blkbits;
        map.m_len = EXT4_MAX_BLOCKS(len, pos, blkbits);
        blklen = map.m_len;

        err = ext4_map_blocks(NULL, inode, &map, 0);
        /*
         * 'err==len' means that all of the blocks have been preallocated,
         * regardless of whether they have been initialized or not. To exclude
         * unwritten extents, we need to check m_flags.
         */
        return err == blklen && (map.m_flags & EXT4_MAP_MAPPED);
}

static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
{
        struct inode *inode = file_inode(iocb->ki_filp);
        ssize_t ret;

        ret = generic_write_checks(iocb, from);
        if (ret <= 0)
                return ret;
        /*
         * If we have encountered a bitmap-format file, the size limit
         * is smaller than s_maxbytes, which is for extent-mapped files.
         */
        if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
                struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);

                if (iocb->ki_pos >= sbi->s_bitmap_maxbytes)
                        return -EFBIG;
                iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
        }
        return iov_iter_count(from);
}

#ifdef CONFIG_FS_DAX
static ssize_t
ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
        struct inode *inode = file_inode(iocb->ki_filp);
        ssize_t ret;

        if (!inode_trylock(inode)) {
                if (iocb->ki_flags & IOCB_NOWAIT)
                        return -EAGAIN;
                inode_lock(inode);
        }
        ret = ext4_write_checks(iocb, from);
        if (ret <= 0)
                goto out;
        ret = file_remove_privs(iocb->ki_filp);
        if (ret)
                goto out;
        ret = file_update_time(iocb->ki_filp);
        if (ret)
                goto out;

        ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);
out:
        inode_unlock(inode);
        if (ret > 0)
                ret = generic_write_sync(iocb, ret);
        return ret;
}
#endif

static ssize_t
ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
        struct inode *inode = file_inode(iocb->ki_filp);
        int o_direct = iocb->ki_flags & IOCB_DIRECT;
        int unaligned_aio = 0;
        int overwrite = 0;
        ssize_t ret;

        if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
                return -EIO;

#ifdef CONFIG_FS_DAX
        if (IS_DAX(inode))
                return ext4_dax_write_iter(iocb, from);
#endif
        if (!o_direct && (iocb->ki_flags & IOCB_NOWAIT))
                return -EOPNOTSUPP;

        if (!inode_trylock(inode)) {
                if (iocb->ki_flags & IOCB_NOWAIT)
                        return -EAGAIN;
                inode_lock(inode);
        }

        ret = ext4_write_checks(iocb, from);
        if (ret <= 0)
                goto out;

        /*
         * Unaligned direct AIO must be serialized among each other as zeroing
         * of partial blocks of two competing unaligned AIOs can result in data
         * corruption.
         */
        if (o_direct && ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
            !is_sync_kiocb(iocb) &&
            ext4_unaligned_aio(inode, from, iocb->ki_pos)) {
                unaligned_aio = 1;
                ext4_unwritten_wait(inode);
        }

        iocb->private = &overwrite;
        /* Check whether we do a DIO overwrite or not */
        if (o_direct && !unaligned_aio) {
                if (ext4_overwrite_io(inode, iocb->ki_pos, iov_iter_count(from))) {
                        if (ext4_should_dioread_nolock(inode))
                                overwrite = 1;
                } else if (iocb->ki_flags & IOCB_NOWAIT) {
                        ret = -EAGAIN;
                        goto out;
                }
        }

        ret = __generic_file_write_iter(iocb, from);
        inode_unlock(inode);

        if (ret > 0)
                ret = generic_write_sync(iocb, ret);

        return ret;

out:
        inode_unlock(inode);
        return ret;
}

#ifdef CONFIG_FS_DAX
static int ext4_dax_huge_fault(struct vm_fault *vmf,
                enum page_entry_size pe_size)
{
        int result;
        handle_t *handle = NULL;
        struct inode *inode = file_inode(vmf->vma->vm_file);
        struct super_block *sb = inode->i_sb;

        /*
         * We have to distinguish real writes from writes which will result in a
         * COW page; COW writes should *not* poke the journal (the file will not
         * be changed). Doing so would cause unintended failures when mounted
         * read-only.
         *
         * We check for VM_SHARED rather than vmf->cow_page since the latter is
         * unset for pe_size != PE_SIZE_PTE (i.e. only in do_cow_fault); for
         * other sizes, dax_iomap_fault will handle splitting / fallback so that
         * we eventually come back with a COW page.
         */
        bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
                (vmf->vma->vm_flags & VM_SHARED);

        if (write) {
                sb_start_pagefault(sb);
                file_update_time(vmf->vma->vm_file);
                down_read(&EXT4_I(inode)->i_mmap_sem);
                handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
                                               EXT4_DATA_TRANS_BLOCKS(sb));
        } else {
                down_read(&EXT4_I(inode)->i_mmap_sem);
        }
        if (!IS_ERR(handle))
                result = dax_iomap_fault(vmf, pe_size, &ext4_iomap_ops);
        else
                result = VM_FAULT_SIGBUS;
        if (write) {
                if (!IS_ERR(handle))
                        ext4_journal_stop(handle);
                up_read(&EXT4_I(inode)->i_mmap_sem);
                sb_end_pagefault(sb);
        } else {
                up_read(&EXT4_I(inode)->i_mmap_sem);
        }

        return result;
}

static int ext4_dax_fault(struct vm_fault *vmf)
{
        return ext4_dax_huge_fault(vmf, PE_SIZE_PTE);
}

static const struct vm_operations_struct ext4_dax_vm_ops = {
        .fault          = ext4_dax_fault,
        .huge_fault     = ext4_dax_huge_fault,
        .page_mkwrite   = ext4_dax_fault,
        .pfn_mkwrite    = ext4_dax_fault,
};
#else
#define ext4_dax_vm_ops ext4_file_vm_ops
#endif

static const struct vm_operations_struct ext4_file_vm_ops = {
        .fault          = ext4_filemap_fault,
        .map_pages      = filemap_map_pages,
        .page_mkwrite   = ext4_page_mkwrite,
};

static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct inode *inode = file->f_mapping->host;

        if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
                return -EIO;

        file_accessed(file);
        if (IS_DAX(file_inode(file))) {
                vma->vm_ops = &ext4_dax_vm_ops;
                vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
        } else {
                vma->vm_ops = &ext4_file_vm_ops;
        }
        return 0;
}

static int ext4_file_open(struct inode * inode, struct file * filp)
{
        struct super_block *sb = inode->i_sb;
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        struct vfsmount *mnt = filp->f_path.mnt;
        struct dentry *dir;
        struct path path;
        char buf[64], *cp;
        int ret;

        if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
                return -EIO;

        if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
                     !sb_rdonly(sb))) {
                sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
                /*
                 * Sample where the filesystem has been mounted and
                 * store it in the superblock for sysadmin convenience
                 * when trying to sort through large numbers of block
                 * devices or filesystem images.
                 */
                memset(buf, 0, sizeof(buf));
                path.mnt = mnt;
                path.dentry = mnt->mnt_root;
                cp = d_path(&path, buf, sizeof(buf));
                if (!IS_ERR(cp)) {
                        handle_t *handle;
                        int err;

                        handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
                        if (IS_ERR(handle))
                                return PTR_ERR(handle);
                        BUFFER_TRACE(sbi->s_sbh, "get_write_access");
                        err = ext4_journal_get_write_access(handle, sbi->s_sbh);
                        if (err) {
                                ext4_journal_stop(handle);
                                return err;
                        }
                        strlcpy(sbi->s_es->s_last_mounted, cp,
                                sizeof(sbi->s_es->s_last_mounted));
                        ext4_handle_dirty_super(handle, sb);
                        ext4_journal_stop(handle);
                }
        }
        if (ext4_encrypted_inode(inode)) {
                ret = fscrypt_get_encryption_info(inode);
                if (ret)
                        return -EACCES;
                if (!fscrypt_has_encryption_key(inode))
                        return -ENOKEY;
        }

        dir = dget_parent(file_dentry(filp));
        if (ext4_encrypted_inode(d_inode(dir)) &&
                        !fscrypt_has_permitted_context(d_inode(dir), inode)) {
                ext4_warning(inode->i_sb,
                             "Inconsistent encryption contexts: %lu/%lu",
                             (unsigned long) d_inode(dir)->i_ino,
                             (unsigned long) inode->i_ino);
                dput(dir);
                return -EPERM;
        }
        dput(dir);
        /*
         * Set up the jbd2_inode if we are opening the inode for
         * writing and the journal is present
         */
        if (filp->f_mode & FMODE_WRITE) {
                ret = ext4_inode_attach_jinode(inode);
                if (ret < 0)
                        return ret;
        }

        filp->f_mode |= FMODE_NOWAIT;
        return dquot_file_open(inode, filp);
}

/*
 * Here we use ext4_map_blocks() to get a block mapping for a extent-based
 * file rather than ext4_ext_walk_space() because we can introduce
 * SEEK_DATA/SEEK_HOLE for block-mapped and extent-mapped file at the same
 * function.  When extent status tree has been fully implemented, it will
 * track all extent status for a file and we can directly use it to
 * retrieve the offset for SEEK_DATA/SEEK_HOLE.
 */

/*
 * When we retrieve the offset for SEEK_DATA/SEEK_HOLE, we would need to
 * lookup page cache to check whether or not there has some data between
 * [startoff, endoff] because, if this range contains an unwritten extent,
 * we determine this extent as a data or a hole according to whether the
 * page cache has data or not.
 */
static int ext4_find_unwritten_pgoff(struct inode *inode,
                                     int whence,
                                     ext4_lblk_t end_blk,
                                     loff_t *offset)
{
        struct pagevec pvec;
        unsigned int blkbits;
        pgoff_t index;
        pgoff_t end;
        loff_t endoff;
        loff_t startoff;
        loff_t lastoff;
        int found = 0;

        blkbits = inode->i_sb->s_blocksize_bits;
        startoff = *offset;
        lastoff = startoff;
        endoff = (loff_t)end_blk << blkbits;

        index = startoff >> PAGE_SHIFT;
        end = (endoff - 1) >> PAGE_SHIFT;

        pagevec_init(&pvec, 0);
        do {
                int i;
                unsigned long nr_pages;

                nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping,
                                        &index, end);
                if (nr_pages == 0)
                        break;

                for (i = 0; i < nr_pages; i++) {
                        struct page *page = pvec.pages[i];
                        struct buffer_head *bh, *head;

                        /*
                         * If current offset is smaller than the page offset,
                         * there is a hole at this offset.
                         */
                        if (whence == SEEK_HOLE && lastoff < endoff &&
                            lastoff < page_offset(pvec.pages[i])) {
                                found = 1;
                                *offset = lastoff;
                                goto out;
                        }

                        lock_page(page);

                        if (unlikely(page->mapping != inode->i_mapping)) {
                                unlock_page(page);
                                continue;
                        }

                        if (!page_has_buffers(page)) {
                                unlock_page(page);
                                continue;
                        }

                        if (page_has_buffers(page)) {
                                lastoff = page_offset(page);
                                bh = head = page_buffers(page);
                                do {
                                        if (lastoff + bh->b_size <= startoff)
                                                goto next;
                                        if (buffer_uptodate(bh) ||
                                            buffer_unwritten(bh)) {
                                                if (whence == SEEK_DATA)
                                                        found = 1;
                                        } else {
                                                if (whence == SEEK_HOLE)
                                                        found = 1;
                                        }
                                        if (found) {
                                                *offset = max_t(loff_t,
                                                        startoff, lastoff);
                                                unlock_page(page);
                                                goto out;
                                        }
next:
                                        lastoff += bh->b_size;
                                        bh = bh->b_this_page;
                                } while (bh != head);
                        }

                        lastoff = page_offset(page) + PAGE_SIZE;
                        unlock_page(page);
                }

                pagevec_release(&pvec);
        } while (index <= end);

        /* There are no pages upto endoff - that would be a hole in there. */
        if (whence == SEEK_HOLE && lastoff < endoff) {
                found = 1;
                *offset = lastoff;
        }
out:
        pagevec_release(&pvec);
        return found;
}

/*
 * ext4_seek_data() retrieves the offset for SEEK_DATA.
 */
static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
{
        struct inode *inode = file->f_mapping->host;
        struct extent_status es;
        ext4_lblk_t start, last, end;
        loff_t dataoff, isize;
        int blkbits;
        int ret;

        inode_lock(inode);

        isize = i_size_read(inode);
        if (offset < 0 || offset >= isize) {
                inode_unlock(inode);
                return -ENXIO;
        }

        blkbits = inode->i_sb->s_blocksize_bits;
        start = offset >> blkbits;
        last = start;
        end = isize >> blkbits;
        dataoff = offset;

        do {
                ret = ext4_get_next_extent(inode, last, end - last + 1, &es);
                if (ret <= 0) {
                        /* No extent found -> no data */
                        if (ret == 0)
                                ret = -ENXIO;
                        inode_unlock(inode);
                        return ret;
                }

                last = es.es_lblk;
                if (last != start)
                        dataoff = (loff_t)last << blkbits;
                if (!ext4_es_is_unwritten(&es))
                        break;

                /*
                 * If there is a unwritten extent at this offset,
                 * it will be as a data or a hole according to page
                 * cache that has data or not.
                 */
                if (ext4_find_unwritten_pgoff(inode, SEEK_DATA,
                                              es.es_lblk + es.es_len, &dataoff))
                        break;
                last += es.es_len;
                dataoff = (loff_t)last << blkbits;
                cond_resched();
        } while (last <= end);

        inode_unlock(inode);

        if (dataoff > isize)
                return -ENXIO;

        return vfs_setpos(file, dataoff, maxsize);
}

/*
 * ext4_seek_hole() retrieves the offset for SEEK_HOLE.
 */
static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
{
        struct inode *inode = file->f_mapping->host;
        struct extent_status es;
        ext4_lblk_t start, last, end;
        loff_t holeoff, isize;
        int blkbits;
        int ret;

        inode_lock(inode);

        isize = i_size_read(inode);
        if (offset < 0 || offset >= isize) {
                inode_unlock(inode);
                return -ENXIO;
        }

        blkbits = inode->i_sb->s_blocksize_bits;
        start = offset >> blkbits;
        last = start;
        end = isize >> blkbits;
        holeoff = offset;

        do {
                ret = ext4_get_next_extent(inode, last, end - last + 1, &es);
                if (ret < 0) {
                        inode_unlock(inode);
                        return ret;
                }
                /* Found a hole? */
                if (ret == 0 || es.es_lblk > last) {
                        if (last != start)
                                holeoff = (loff_t)last << blkbits;
                        break;
                }
                /*
                 * If there is a unwritten extent at this offset,
                 * it will be as a data or a hole according to page
                 * cache that has data or not.
                 */
                if (ext4_es_is_unwritten(&es) &&
                    ext4_find_unwritten_pgoff(inode, SEEK_HOLE,
                                              last + es.es_len, &holeoff))
                        break;

                last += es.es_len;
                holeoff = (loff_t)last << blkbits;
                cond_resched();
        } while (last <= end);

        inode_unlock(inode);

        if (holeoff > isize)
                holeoff = isize;

        return vfs_setpos(file, holeoff, maxsize);
}

/*
 * ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
 * by calling generic_file_llseek_size() with the appropriate maxbytes
 * value for each.
 */
loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
{
        struct inode *inode = file->f_mapping->host;
        loff_t maxbytes;

        if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
                maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
        else
                maxbytes = inode->i_sb->s_maxbytes;

        switch (whence) {
        case SEEK_SET:
        case SEEK_CUR:
        case SEEK_END:
                return generic_file_llseek_size(file, offset, whence,
                                                maxbytes, i_size_read(inode));
        case SEEK_DATA:
                return ext4_seek_data(file, offset, maxbytes);
        case SEEK_HOLE:
                return ext4_seek_hole(file, offset, maxbytes);
        }

        return -EINVAL;
}

const struct file_operations ext4_file_operations = {
        .llseek         = ext4_llseek,
        .read_iter      = ext4_file_read_iter,
        .write_iter     = ext4_file_write_iter,
        .unlocked_ioctl = ext4_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = ext4_compat_ioctl,
#endif
        .mmap           = ext4_file_mmap,
        .open           = ext4_file_open,
        .release        = ext4_release_file,
        .fsync          = ext4_sync_file,
        .get_unmapped_area = thp_get_unmapped_area,
        .splice_read    = generic_file_splice_read,
        .splice_write   = iter_file_splice_write,
        .fallocate      = ext4_fallocate,
};

const struct inode_operations ext4_file_inode_operations = {
        .setattr        = ext4_setattr,
        .getattr        = ext4_file_getattr,
        .listxattr      = ext4_listxattr,
        .get_acl        = ext4_get_acl,
        .set_acl        = ext4_set_acl,
        .fiemap         = ext4_fiemap,
};