/*
 *  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/quotaops.h>
#include <linux/pagevec.h>
#include <linux/uio.h>
#include "ext4.h"
#include "ext4_jbd2.h"
#include "xattr.h"
#include "acl.h"

/*
 * 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;
}

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

        /*
         * Unaligned direct AIO must be serialized; see comment above
         * In the case of O_APPEND, assume that we must always serialize
         */
        if (o_direct &&
            ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) &&
            !is_sync_kiocb(iocb) &&
            (iocb->ki_flags & IOCB_APPEND ||
             ext4_unaligned_aio(inode, from, iocb->ki_pos))) {
                aio_mutex = ext4_aio_mutex(inode);
                mutex_lock(aio_mutex);
                ext4_unwritten_wait(inode);
        }

        mutex_lock(&inode->i_mutex);
        ret = generic_write_checks(iocb, from);
        if (ret <= 0)
                goto out;

        /*
         * 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) {
                        ret = -EFBIG;
                        goto out;
                }
                iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
        }

        iocb->private = &overwrite;
        if (o_direct) {
                size_t length = iov_iter_count(from);
                loff_t pos = iocb->ki_pos;
                blk_start_plug(&plug);

                /* check whether we do a DIO overwrite or not */
                if (ext4_should_dioread_nolock(inode) && !aio_mutex &&
                    !file->f_mapping->nrpages && pos + length <= i_size_read(inode)) {
                        struct ext4_map_blocks map;
                        unsigned int blkbits = inode->i_blkbits;
                        int err, len;

                        map.m_lblk = pos >> blkbits;
                        map.m_len = (EXT4_BLOCK_ALIGN(pos + length, blkbits) >> blkbits)
                                - map.m_lblk;
                        len = map.m_len;

                        err = ext4_map_blocks(NULL, inode, &map, 0);
                        /*
                         * 'err==len' means that all of blocks has
                         * been preallocated no matter they are
                         * initialized or not.  For excluding
                         * unwritten extents, we need to check
                         * m_flags.  There are two conditions that
                         * indicate for initialized extents.  1) If we
                         * hit extent cache, EXT4_MAP_MAPPED flag is
                         * returned; 2) If we do a real lookup,
                         * non-flags are returned.  So we should check
                         * these two conditions.
                         */
                        if (err == len && (map.m_flags & EXT4_MAP_MAPPED))
                                overwrite = 1;
                }
        }

        ret = __generic_file_write_iter(iocb, from);
        mutex_unlock(&inode->i_mutex);

        if (ret > 0) {
                ssize_t err;

                err = generic_write_sync(file, iocb->ki_pos - ret, ret);
                if (err < 0)
                        ret = err;
        }
        if (o_direct)
                blk_finish_plug(&plug);

        if (aio_mutex)
                mutex_unlock(aio_mutex);
        return ret;

out:
        mutex_unlock(&inode->i_mutex);
        if (aio_mutex)
                mutex_unlock(aio_mutex);
        return ret;
}

#ifdef CONFIG_FS_DAX
static int ext4_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        return dax_fault(vma, vmf, ext4_get_block);
                                        /* Is this the right get_block? */
}

static int ext4_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        return dax_mkwrite(vma, vmf, ext4_get_block);
}

static const struct vm_operations_struct ext4_dax_vm_ops = {
        .fault          = ext4_dax_fault,
        .page_mkwrite   = ext4_dax_mkwrite,
        .pfn_mkwrite    = dax_pfn_mkwrite,
};
#else
#define ext4_dax_vm_ops ext4_file_vm_ops
#endif

static const struct vm_operations_struct ext4_file_vm_ops = {
        .fault          = 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 (ext4_encrypted_inode(inode)) {
                int err = ext4_generate_encryption_key(inode);
                if (err)
                        return 0;
        }
        file_accessed(file);
        if (IS_DAX(file_inode(file))) {
                vma->vm_ops = &ext4_dax_vm_ops;
                vma->vm_flags |= VM_MIXEDMAP;
        } 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 path path;
        char buf[64], *cp;
        int ret;

        if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
                     !(sb->s_flags & MS_RDONLY))) {
                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);
                }
        }
        /*
         * 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;
        }
        ret = dquot_file_open(inode, filp);
        if (!ret && ext4_encrypted_inode(inode)) {
                ret = ext4_generate_encryption_key(inode);
                if (ret)
                        ret = -EACCES;
        }
        return ret;
}

/*
 * 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,
                                     struct ext4_map_blocks *map,
                                     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)(map->m_lblk + map->m_len) << blkbits;

        index = startoff >> PAGE_CACHE_SHIFT;
        end = endoff >> PAGE_CACHE_SHIFT;

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

                num = min_t(pgoff_t, end - index, PAGEVEC_SIZE);
                nr_pages = pagevec_lookup(&pvec, inode->i_mapping, index,
                                          (pgoff_t)num);
                if (nr_pages == 0) {
                        if (whence == SEEK_DATA)
                                break;

                        BUG_ON(whence != SEEK_HOLE);
                        /*
                         * If this is the first time to go into the loop and
                         * offset is not beyond the end offset, it will be a
                         * hole at this offset
                         */
                        if (lastoff == startoff || lastoff < endoff)
                                found = 1;
                        break;
                }

                /*
                 * If this is the first time to go into the loop and
                 * offset is smaller than the first page offset, it will be a
                 * hole at this offset.
                 */
                if (lastoff == startoff && whence == SEEK_HOLE &&
                    lastoff < page_offset(pvec.pages[0])) {
                        found = 1;
                        break;
                }

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

                        /*
                         * If the current offset is not beyond the end of given
                         * range, it will be a hole.
                         */
                        if (lastoff < endoff && whence == SEEK_HOLE &&
                            page->index > end) {
                                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 (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;
                                        }
                                        lastoff += bh->b_size;
                                        bh = bh->b_this_page;
                                } while (bh != head);
                        }

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

                /*
                 * The no. of pages is less than our desired, that would be a
                 * hole in there.
                 */
                if (nr_pages < num && whence == SEEK_HOLE) {
                        found = 1;
                        *offset = lastoff;
                        break;
                }

                index = pvec.pages[i - 1]->index + 1;
                pagevec_release(&pvec);
        } while (index <= end);

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 ext4_map_blocks map;
        struct extent_status es;
        ext4_lblk_t start, last, end;
        loff_t dataoff, isize;
        int blkbits;
        int ret = 0;

        mutex_lock(&inode->i_mutex);

        isize = i_size_read(inode);
        if (offset >= isize) {
                mutex_unlock(&inode->i_mutex);
                return -ENXIO;
        }

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

        do {
                map.m_lblk = last;
                map.m_len = end - last + 1;
                ret = ext4_map_blocks(NULL, inode, &map, 0);
                if (ret > 0 && !(map.m_flags & EXT4_MAP_UNWRITTEN)) {
                        if (last != start)
                                dataoff = (loff_t)last << blkbits;
                        break;
                }

                /*
                 * If there is a delay extent at this offset,
                 * it will be as a data.
                 */
                ext4_es_find_delayed_extent_range(inode, last, last, &es);
                if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
                        if (last != start)
                                dataoff = (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 (map.m_flags & EXT4_MAP_UNWRITTEN) {
                        int unwritten;
                        unwritten = ext4_find_unwritten_pgoff(inode, SEEK_DATA,
                                                              &map, &dataoff);
                        if (unwritten)
                                break;
                }

                last++;
                dataoff = (loff_t)last << blkbits;
        } while (last <= end);

        mutex_unlock(&inode->i_mutex);

        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 ext4_map_blocks map;
        struct extent_status es;
        ext4_lblk_t start, last, end;
        loff_t holeoff, isize;
        int blkbits;
        int ret = 0;

        mutex_lock(&inode->i_mutex);

        isize = i_size_read(inode);
        if (offset >= isize) {
                mutex_unlock(&inode->i_mutex);
                return -ENXIO;
        }

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

        do {
                map.m_lblk = last;
                map.m_len = end - last + 1;
                ret = ext4_map_blocks(NULL, inode, &map, 0);
                if (ret > 0 && !(map.m_flags & EXT4_MAP_UNWRITTEN)) {
                        last += ret;
                        holeoff = (loff_t)last << blkbits;
                        continue;
                }

                /*
                 * If there is a delay extent at this offset,
                 * we will skip this extent.
                 */
                ext4_es_find_delayed_extent_range(inode, last, last, &es);
                if (es.es_len != 0 && in_range(last, es.es_lblk, es.es_len)) {
                        last = es.es_lblk + es.es_len;
                        holeoff = (loff_t)last << blkbits;
                        continue;
                }

                /*
                 * 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 (map.m_flags & EXT4_MAP_UNWRITTEN) {
                        int unwritten;
                        unwritten = ext4_find_unwritten_pgoff(inode, SEEK_HOLE,
                                                              &map, &holeoff);
                        if (!unwritten) {
                                last += ret;
                                holeoff = (loff_t)last << blkbits;
                                continue;
                        }
                }

                /* find a hole */
                break;
        } while (last <= end);

        mutex_unlock(&inode->i_mutex);

        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      = generic_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,
        .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_getattr,
        .setxattr       = generic_setxattr,
        .getxattr       = generic_getxattr,
        .listxattr      = ext4_listxattr,
        .removexattr    = generic_removexattr,
        .get_acl        = ext4_get_acl,
        .set_acl        = ext4_set_acl,
        .fiemap         = ext4_fiemap,
};