Avoid beyond bounds copy while caching ACL

[zen-stable.git] / fs / xfs / xfs_file.c

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_trans.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_inode_item.h"
#include "xfs_bmap.h"
#include "xfs_error.h"
#include "xfs_vnodeops.h"
#include "xfs_da_btree.h"
#include "xfs_ioctl.h"
#include "xfs_trace.h"

#include <linux/dcache.h>
#include <linux/falloc.h>

static const struct vm_operations_struct xfs_file_vm_ops;

/*
 * Locking primitives for read and write IO paths to ensure we consistently use
 * and order the inode->i_mutex, ip->i_lock and ip->i_iolock.
 */
static inline void
xfs_rw_ilock(
        struct xfs_inode        *ip,
        int                     type)
{
        if (type & XFS_IOLOCK_EXCL)
                mutex_lock(&VFS_I(ip)->i_mutex);
        xfs_ilock(ip, type);
}

static inline void
xfs_rw_iunlock(
        struct xfs_inode        *ip,
        int                     type)
{
        xfs_iunlock(ip, type);
        if (type & XFS_IOLOCK_EXCL)
                mutex_unlock(&VFS_I(ip)->i_mutex);
}

static inline void
xfs_rw_ilock_demote(
        struct xfs_inode        *ip,
        int                     type)
{
        xfs_ilock_demote(ip, type);
        if (type & XFS_IOLOCK_EXCL)
                mutex_unlock(&VFS_I(ip)->i_mutex);
}

/*
 *      xfs_iozero
 *
 *      xfs_iozero clears the specified range of buffer supplied,
 *      and marks all the affected blocks as valid and modified.  If
 *      an affected block is not allocated, it will be allocated.  If
 *      an affected block is not completely overwritten, and is not
 *      valid before the operation, it will be read from disk before
 *      being partially zeroed.
 */
STATIC int
xfs_iozero(
        struct xfs_inode        *ip,    /* inode                        */
        loff_t                  pos,    /* offset in file               */
        size_t                  count)  /* size of data to zero         */
{
        struct page             *page;
        struct address_space    *mapping;
        int                     status;

        mapping = VFS_I(ip)->i_mapping;
        do {
                unsigned offset, bytes;
                void *fsdata;

                offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
                bytes = PAGE_CACHE_SIZE - offset;
                if (bytes > count)
                        bytes = count;

                status = pagecache_write_begin(NULL, mapping, pos, bytes,
                                        AOP_FLAG_UNINTERRUPTIBLE,
                                        &page, &fsdata);
                if (status)
                        break;

                zero_user(page, offset, bytes);

                status = pagecache_write_end(NULL, mapping, pos, bytes, bytes,
                                        page, fsdata);
                WARN_ON(status <= 0); /* can't return less than zero! */
                pos += bytes;
                count -= bytes;
                status = 0;
        } while (count);

        return (-status);
}

/*
 * Fsync operations on directories are much simpler than on regular files,
 * as there is no file data to flush, and thus also no need for explicit
 * cache flush operations, and there are no non-transaction metadata updates
 * on directories either.
 */
STATIC int
xfs_dir_fsync(
        struct file             *file,
        loff_t                  start,
        loff_t                  end,
        int                     datasync)
{
        struct xfs_inode        *ip = XFS_I(file->f_mapping->host);
        struct xfs_mount        *mp = ip->i_mount;
        xfs_lsn_t               lsn = 0;

        trace_xfs_dir_fsync(ip);

        xfs_ilock(ip, XFS_ILOCK_SHARED);
        if (xfs_ipincount(ip))
                lsn = ip->i_itemp->ili_last_lsn;
        xfs_iunlock(ip, XFS_ILOCK_SHARED);

        if (!lsn)
                return 0;
        return _xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, NULL);
}

STATIC int
xfs_file_fsync(
        struct file             *file,
        loff_t                  start,
        loff_t                  end,
        int                     datasync)
{
        struct inode            *inode = file->f_mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        int                     error = 0;
        int                     log_flushed = 0;
        xfs_lsn_t               lsn = 0;

        trace_xfs_file_fsync(ip);

        error = filemap_write_and_wait_range(inode->i_mapping, start, end);
        if (error)
                return error;

        if (XFS_FORCED_SHUTDOWN(mp))
                return -XFS_ERROR(EIO);

        xfs_iflags_clear(ip, XFS_ITRUNCATED);

        if (mp->m_flags & XFS_MOUNT_BARRIER) {
                /*
                 * If we have an RT and/or log subvolume we need to make sure
                 * to flush the write cache the device used for file data
                 * first.  This is to ensure newly written file data make
                 * it to disk before logging the new inode size in case of
                 * an extending write.
                 */
                if (XFS_IS_REALTIME_INODE(ip))
                        xfs_blkdev_issue_flush(mp->m_rtdev_targp);
                else if (mp->m_logdev_targp != mp->m_ddev_targp)
                        xfs_blkdev_issue_flush(mp->m_ddev_targp);
        }

        /*
         * We always need to make sure that the required inode state is safe on
         * disk.  The inode might be clean but we still might need to force the
         * log because of committed transactions that haven't hit the disk yet.
         * Likewise, there could be unflushed non-transactional changes to the
         * inode core that have to go to disk and this requires us to issue
         * a synchronous transaction to capture these changes correctly.
         *
         * This code relies on the assumption that if the i_update_core field
         * of the inode is clear and the inode is unpinned then it is clean
         * and no action is required.
         */
        xfs_ilock(ip, XFS_ILOCK_SHARED);

        /*
         * First check if the VFS inode is marked dirty.  All the dirtying
         * of non-transactional updates do not go through mark_inode_dirty*,
         * which allows us to distinguish between pure timestamp updates
         * and i_size updates which need to be caught for fdatasync.
         * After that also check for the dirty state in the XFS inode, which
         * might gets cleared when the inode gets written out via the AIL
         * or xfs_iflush_cluster.
         */
        if (((inode->i_state & I_DIRTY_DATASYNC) ||
            ((inode->i_state & I_DIRTY_SYNC) && !datasync)) &&
            ip->i_update_core) {
                /*
                 * Kick off a transaction to log the inode core to get the
                 * updates.  The sync transaction will also force the log.
                 */
                xfs_iunlock(ip, XFS_ILOCK_SHARED);
                tp = xfs_trans_alloc(mp, XFS_TRANS_FSYNC_TS);
                error = xfs_trans_reserve(tp, 0,
                                XFS_FSYNC_TS_LOG_RES(mp), 0, 0, 0);
                if (error) {
                        xfs_trans_cancel(tp, 0);
                        return -error;
                }
                xfs_ilock(ip, XFS_ILOCK_EXCL);

                /*
                 * Note - it's possible that we might have pushed ourselves out
                 * of the way during trans_reserve which would flush the inode.
                 * But there's no guarantee that the inode buffer has actually
                 * gone out yet (it's delwri).  Plus the buffer could be pinned
                 * anyway if it's part of an inode in another recent
                 * transaction.  So we play it safe and fire off the
                 * transaction anyway.
                 */
                xfs_trans_ijoin(tp, ip, 0);
                xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
                error = xfs_trans_commit(tp, 0);

                lsn = ip->i_itemp->ili_last_lsn;
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
        } else {
                /*
                 * Timestamps/size haven't changed since last inode flush or
                 * inode transaction commit.  That means either nothing got
                 * written or a transaction committed which caught the updates.
                 * If the latter happened and the transaction hasn't hit the
                 * disk yet, the inode will be still be pinned.  If it is,
                 * force the log.
                 */
                if (xfs_ipincount(ip))
                        lsn = ip->i_itemp->ili_last_lsn;
                xfs_iunlock(ip, XFS_ILOCK_SHARED);
        }

        if (!error && lsn)
                error = _xfs_log_force_lsn(mp, lsn, XFS_LOG_SYNC, &log_flushed);

        /*
         * If we only have a single device, and the log force about was
         * a no-op we might have to flush the data device cache here.
         * This can only happen for fdatasync/O_DSYNC if we were overwriting
         * an already allocated file and thus do not have any metadata to
         * commit.
         */
        if ((mp->m_flags & XFS_MOUNT_BARRIER) &&
            mp->m_logdev_targp == mp->m_ddev_targp &&
            !XFS_IS_REALTIME_INODE(ip) &&
            !log_flushed)
                xfs_blkdev_issue_flush(mp->m_ddev_targp);

        return -error;
}

STATIC ssize_t
xfs_file_aio_read(
        struct kiocb            *iocb,
        const struct iovec      *iovp,
        unsigned long           nr_segs,
        loff_t                  pos)
{
        struct file             *file = iocb->ki_filp;
        struct inode            *inode = file->f_mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        size_t                  size = 0;
        ssize_t                 ret = 0;
        int                     ioflags = 0;
        xfs_fsize_t             n;
        unsigned long           seg;

        XFS_STATS_INC(xs_read_calls);

        BUG_ON(iocb->ki_pos != pos);

        if (unlikely(file->f_flags & O_DIRECT))
                ioflags |= IO_ISDIRECT;
        if (file->f_mode & FMODE_NOCMTIME)
                ioflags |= IO_INVIS;

        /* START copy & waste from filemap.c */
        for (seg = 0; seg < nr_segs; seg++) {
                const struct iovec *iv = &iovp[seg];

                /*
                 * If any segment has a negative length, or the cumulative
                 * length ever wraps negative then return -EINVAL.
                 */
                size += iv->iov_len;
                if (unlikely((ssize_t)(size|iv->iov_len) < 0))
                        return XFS_ERROR(-EINVAL);
        }
        /* END copy & waste from filemap.c */

        if (unlikely(ioflags & IO_ISDIRECT)) {
                xfs_buftarg_t   *target =
                        XFS_IS_REALTIME_INODE(ip) ?
                                mp->m_rtdev_targp : mp->m_ddev_targp;
                if ((iocb->ki_pos & target->bt_smask) ||
                    (size & target->bt_smask)) {
                        if (iocb->ki_pos == i_size_read(inode))
                                return 0;
                        return -XFS_ERROR(EINVAL);
                }
        }

        n = XFS_MAXIOFFSET(mp) - iocb->ki_pos;
        if (n <= 0 || size == 0)
                return 0;

        if (n < size)
                size = n;

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        /*
         * Locking is a bit tricky here. If we take an exclusive lock
         * for direct IO, we effectively serialise all new concurrent
         * read IO to this file and block it behind IO that is currently in
         * progress because IO in progress holds the IO lock shared. We only
         * need to hold the lock exclusive to blow away the page cache, so
         * only take lock exclusively if the page cache needs invalidation.
         * This allows the normal direct IO case of no page cache pages to
         * proceeed concurrently without serialisation.
         */
        xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
        if ((ioflags & IO_ISDIRECT) && inode->i_mapping->nrpages) {
                xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
                xfs_rw_ilock(ip, XFS_IOLOCK_EXCL);

                if (inode->i_mapping->nrpages) {
                        ret = -xfs_flushinval_pages(ip,
                                        (iocb->ki_pos & PAGE_CACHE_MASK),
                                        -1, FI_REMAPF_LOCKED);
                        if (ret) {
                                xfs_rw_iunlock(ip, XFS_IOLOCK_EXCL);
                                return ret;
                        }
                }
                xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
        }

        trace_xfs_file_read(ip, size, iocb->ki_pos, ioflags);

        ret = generic_file_aio_read(iocb, iovp, nr_segs, iocb->ki_pos);
        if (ret > 0)
                XFS_STATS_ADD(xs_read_bytes, ret);

        xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
        return ret;
}

STATIC ssize_t
xfs_file_splice_read(
        struct file             *infilp,
        loff_t                  *ppos,
        struct pipe_inode_info  *pipe,
        size_t                  count,
        unsigned int            flags)
{
        struct xfs_inode        *ip = XFS_I(infilp->f_mapping->host);
        int                     ioflags = 0;
        ssize_t                 ret;

        XFS_STATS_INC(xs_read_calls);

        if (infilp->f_mode & FMODE_NOCMTIME)
                ioflags |= IO_INVIS;

        if (XFS_FORCED_SHUTDOWN(ip->i_mount))
                return -EIO;

        xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);

        trace_xfs_file_splice_read(ip, count, *ppos, ioflags);

        ret = generic_file_splice_read(infilp, ppos, pipe, count, flags);
        if (ret > 0)
                XFS_STATS_ADD(xs_read_bytes, ret);

        xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
        return ret;
}

/*
 * xfs_file_splice_write() does not use xfs_rw_ilock() because
 * generic_file_splice_write() takes the i_mutex itself. This, in theory,
 * couuld cause lock inversions between the aio_write path and the splice path
 * if someone is doing concurrent splice(2) based writes and write(2) based
 * writes to the same inode. The only real way to fix this is to re-implement
 * the generic code here with correct locking orders.
 */
STATIC ssize_t
xfs_file_splice_write(
        struct pipe_inode_info  *pipe,
        struct file             *outfilp,
        loff_t                  *ppos,
        size_t                  count,
        unsigned int            flags)
{
        struct inode            *inode = outfilp->f_mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        int                     ioflags = 0;
        ssize_t                 ret;

        XFS_STATS_INC(xs_write_calls);

        if (outfilp->f_mode & FMODE_NOCMTIME)
                ioflags |= IO_INVIS;

        if (XFS_FORCED_SHUTDOWN(ip->i_mount))
                return -EIO;

        xfs_ilock(ip, XFS_IOLOCK_EXCL);

        trace_xfs_file_splice_write(ip, count, *ppos, ioflags);

        ret = generic_file_splice_write(pipe, outfilp, ppos, count, flags);
        if (ret > 0)
                XFS_STATS_ADD(xs_write_bytes, ret);

        xfs_iunlock(ip, XFS_IOLOCK_EXCL);
        return ret;
}

/*
 * This routine is called to handle zeroing any space in the last
 * block of the file that is beyond the EOF.  We do this since the
 * size is being increased without writing anything to that block
 * and we don't want anyone to read the garbage on the disk.
 */
STATIC int                              /* error (positive) */
xfs_zero_last_block(
        xfs_inode_t     *ip,
        xfs_fsize_t     offset,
        xfs_fsize_t     isize)
{
        xfs_fileoff_t   last_fsb;
        xfs_mount_t     *mp = ip->i_mount;
        int             nimaps;
        int             zero_offset;
        int             zero_len;
        int             error = 0;
        xfs_bmbt_irec_t imap;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

        zero_offset = XFS_B_FSB_OFFSET(mp, isize);
        if (zero_offset == 0) {
                /*
                 * There are no extra bytes in the last block on disk to
                 * zero, so return.
                 */
                return 0;
        }

        last_fsb = XFS_B_TO_FSBT(mp, isize);
        nimaps = 1;
        error = xfs_bmapi_read(ip, last_fsb, 1, &imap, &nimaps, 0);
        if (error)
                return error;
        ASSERT(nimaps > 0);
        /*
         * If the block underlying isize is just a hole, then there
         * is nothing to zero.
         */
        if (imap.br_startblock == HOLESTARTBLOCK) {
                return 0;
        }
        /*
         * Zero the part of the last block beyond the EOF, and write it
         * out sync.  We need to drop the ilock while we do this so we
         * don't deadlock when the buffer cache calls back to us.
         */
        xfs_iunlock(ip, XFS_ILOCK_EXCL);

        zero_len = mp->m_sb.sb_blocksize - zero_offset;
        if (isize + zero_len > offset)
                zero_len = offset - isize;
        error = xfs_iozero(ip, isize, zero_len);

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        ASSERT(error >= 0);
        return error;
}

/*
 * Zero any on disk space between the current EOF and the new,
 * larger EOF.  This handles the normal case of zeroing the remainder
 * of the last block in the file and the unusual case of zeroing blocks
 * out beyond the size of the file.  This second case only happens
 * with fixed size extents and when the system crashes before the inode
 * size was updated but after blocks were allocated.  If fill is set,
 * then any holes in the range are filled and zeroed.  If not, the holes
 * are left alone as holes.
 */

int                                     /* error (positive) */
xfs_zero_eof(
        xfs_inode_t     *ip,
        xfs_off_t       offset,         /* starting I/O offset */
        xfs_fsize_t     isize)          /* current inode size */
{
        xfs_mount_t     *mp = ip->i_mount;
        xfs_fileoff_t   start_zero_fsb;
        xfs_fileoff_t   end_zero_fsb;
        xfs_fileoff_t   zero_count_fsb;
        xfs_fileoff_t   last_fsb;
        xfs_fileoff_t   zero_off;
        xfs_fsize_t     zero_len;
        int             nimaps;
        int             error = 0;
        xfs_bmbt_irec_t imap;

        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_IOLOCK_EXCL));
        ASSERT(offset > isize);

        /*
         * First handle zeroing the block on which isize resides.
         * We only zero a part of that block so it is handled specially.
         */
        error = xfs_zero_last_block(ip, offset, isize);
        if (error) {
                ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_IOLOCK_EXCL));
                return error;
        }

        /*
         * Calculate the range between the new size and the old
         * where blocks needing to be zeroed may exist.  To get the
         * block where the last byte in the file currently resides,
         * we need to subtract one from the size and truncate back
         * to a block boundary.  We subtract 1 in case the size is
         * exactly on a block boundary.
         */
        last_fsb = isize ? XFS_B_TO_FSBT(mp, isize - 1) : (xfs_fileoff_t)-1;
        start_zero_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)isize);
        end_zero_fsb = XFS_B_TO_FSBT(mp, offset - 1);
        ASSERT((xfs_sfiloff_t)last_fsb < (xfs_sfiloff_t)start_zero_fsb);
        if (last_fsb == end_zero_fsb) {
                /*
                 * The size was only incremented on its last block.
                 * We took care of that above, so just return.
                 */
                return 0;
        }

        ASSERT(start_zero_fsb <= end_zero_fsb);
        while (start_zero_fsb <= end_zero_fsb) {
                nimaps = 1;
                zero_count_fsb = end_zero_fsb - start_zero_fsb + 1;
                error = xfs_bmapi_read(ip, start_zero_fsb, zero_count_fsb,
                                          &imap, &nimaps, 0);
                if (error) {
                        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_IOLOCK_EXCL));
                        return error;
                }
                ASSERT(nimaps > 0);

                if (imap.br_state == XFS_EXT_UNWRITTEN ||
                    imap.br_startblock == HOLESTARTBLOCK) {
                        /*
                         * This loop handles initializing pages that were
                         * partially initialized by the code below this
                         * loop. It basically zeroes the part of the page
                         * that sits on a hole and sets the page as P_HOLE
                         * and calls remapf if it is a mapped file.
                         */
                        start_zero_fsb = imap.br_startoff + imap.br_blockcount;
                        ASSERT(start_zero_fsb <= (end_zero_fsb + 1));
                        continue;
                }

                /*
                 * There are blocks we need to zero.
                 * Drop the inode lock while we're doing the I/O.
                 * We'll still have the iolock to protect us.
                 */
                xfs_iunlock(ip, XFS_ILOCK_EXCL);

                zero_off = XFS_FSB_TO_B(mp, start_zero_fsb);
                zero_len = XFS_FSB_TO_B(mp, imap.br_blockcount);

                if ((zero_off + zero_len) > offset)
                        zero_len = offset - zero_off;

                error = xfs_iozero(ip, zero_off, zero_len);
                if (error) {
                        goto out_lock;
                }

                start_zero_fsb = imap.br_startoff + imap.br_blockcount;
                ASSERT(start_zero_fsb <= (end_zero_fsb + 1));

                xfs_ilock(ip, XFS_ILOCK_EXCL);
        }

        return 0;

out_lock:
        xfs_ilock(ip, XFS_ILOCK_EXCL);
        ASSERT(error >= 0);
        return error;
}

/*
 * Common pre-write limit and setup checks.
 *
 * Called with the iolocked held either shared and exclusive according to
 * @iolock, and returns with it held.  Might upgrade the iolock to exclusive
 * if called for a direct write beyond i_size.
 */
STATIC ssize_t
xfs_file_aio_write_checks(
        struct file             *file,
        loff_t                  *pos,
        size_t                  *count,
        int                     *iolock)
{
        struct inode            *inode = file->f_mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        int                     error = 0;

        xfs_rw_ilock(ip, XFS_ILOCK_EXCL);
restart:
        error = generic_write_checks(file, pos, count, S_ISBLK(inode->i_mode));
        if (error) {
                xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
                return error;
        }

        if (likely(!(file->f_mode & FMODE_NOCMTIME)))
                file_update_time(file);

        /*
         * If the offset is beyond the size of the file, we need to zero any
         * blocks that fall between the existing EOF and the start of this
         * write.  If zeroing is needed and we are currently holding the
         * iolock shared, we need to update it to exclusive which involves
         * dropping all locks and relocking to maintain correct locking order.
         * If we do this, restart the function to ensure all checks and values
         * are still valid.
         */
        if (*pos > i_size_read(inode)) {
                if (*iolock == XFS_IOLOCK_SHARED) {
                        xfs_rw_iunlock(ip, XFS_ILOCK_EXCL | *iolock);
                        *iolock = XFS_IOLOCK_EXCL;
                        xfs_rw_ilock(ip, XFS_ILOCK_EXCL | *iolock);
                        goto restart;
                }
                error = -xfs_zero_eof(ip, *pos, i_size_read(inode));
        }
        xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
        if (error)
                return error;

        /*
         * If we're writing the file then make sure to clear the setuid and
         * setgid bits if the process is not being run by root.  This keeps
         * people from modifying setuid and setgid binaries.
         */
        return file_remove_suid(file);

}

/*
 * xfs_file_dio_aio_write - handle direct IO writes
 *
 * Lock the inode appropriately to prepare for and issue a direct IO write.
 * By separating it from the buffered write path we remove all the tricky to
 * follow locking changes and looping.
 *
 * If there are cached pages or we're extending the file, we need IOLOCK_EXCL
 * until we're sure the bytes at the new EOF have been zeroed and/or the cached
 * pages are flushed out.
 *
 * In most cases the direct IO writes will be done holding IOLOCK_SHARED
 * allowing them to be done in parallel with reads and other direct IO writes.
 * However, if the IO is not aligned to filesystem blocks, the direct IO layer
 * needs to do sub-block zeroing and that requires serialisation against other
 * direct IOs to the same block. In this case we need to serialise the
 * submission of the unaligned IOs so that we don't get racing block zeroing in
 * the dio layer.  To avoid the problem with aio, we also need to wait for
 * outstanding IOs to complete so that unwritten extent conversion is completed
 * before we try to map the overlapping block. This is currently implemented by
 * hitting it with a big hammer (i.e. inode_dio_wait()).
 *
 * Returns with locks held indicated by @iolock and errors indicated by
 * negative return values.
 */
STATIC ssize_t
xfs_file_dio_aio_write(
        struct kiocb            *iocb,
        const struct iovec      *iovp,
        unsigned long           nr_segs,
        loff_t                  pos,
        size_t                  ocount)
{
        struct file             *file = iocb->ki_filp;
        struct address_space    *mapping = file->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        ssize_t                 ret = 0;
        size_t                  count = ocount;
        int                     unaligned_io = 0;
        int                     iolock;
        struct xfs_buftarg      *target = XFS_IS_REALTIME_INODE(ip) ?
                                        mp->m_rtdev_targp : mp->m_ddev_targp;

        if ((pos & target->bt_smask) || (count & target->bt_smask))
                return -XFS_ERROR(EINVAL);

        if ((pos & mp->m_blockmask) || ((pos + count) & mp->m_blockmask))
                unaligned_io = 1;

        /*
         * We don't need to take an exclusive lock unless there page cache needs
         * to be invalidated or unaligned IO is being executed. We don't need to
         * consider the EOF extension case here because
         * xfs_file_aio_write_checks() will relock the inode as necessary for
         * EOF zeroing cases and fill out the new inode size as appropriate.
         */
        if (unaligned_io || mapping->nrpages)
                iolock = XFS_IOLOCK_EXCL;
        else
                iolock = XFS_IOLOCK_SHARED;
        xfs_rw_ilock(ip, iolock);

        /*
         * Recheck if there are cached pages that need invalidate after we got
         * the iolock to protect against other threads adding new pages while
         * we were waiting for the iolock.
         */
        if (mapping->nrpages && iolock == XFS_IOLOCK_SHARED) {
                xfs_rw_iunlock(ip, iolock);
                iolock = XFS_IOLOCK_EXCL;
                xfs_rw_ilock(ip, iolock);
        }

        ret = xfs_file_aio_write_checks(file, &pos, &count, &iolock);
        if (ret)
                goto out;

        if (mapping->nrpages) {
                ret = -xfs_flushinval_pages(ip, (pos & PAGE_CACHE_MASK), -1,
                                                        FI_REMAPF_LOCKED);
                if (ret)
                        goto out;
        }

        /*
         * If we are doing unaligned IO, wait for all other IO to drain,
         * otherwise demote the lock if we had to flush cached pages
         */
        if (unaligned_io)
                inode_dio_wait(inode);
        else if (iolock == XFS_IOLOCK_EXCL) {
                xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
                iolock = XFS_IOLOCK_SHARED;
        }

        trace_xfs_file_direct_write(ip, count, iocb->ki_pos, 0);
        ret = generic_file_direct_write(iocb, iovp,
                        &nr_segs, pos, &iocb->ki_pos, count, ocount);

out:
        xfs_rw_iunlock(ip, iolock);

        /* No fallback to buffered IO on errors for XFS. */
        ASSERT(ret < 0 || ret == count);
        return ret;
}

STATIC ssize_t
xfs_file_buffered_aio_write(
        struct kiocb            *iocb,
        const struct iovec      *iovp,
        unsigned long           nr_segs,
        loff_t                  pos,
        size_t                  ocount)
{
        struct file             *file = iocb->ki_filp;
        struct address_space    *mapping = file->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        ssize_t                 ret;
        int                     enospc = 0;
        int                     iolock = XFS_IOLOCK_EXCL;
        size_t                  count = ocount;

        xfs_rw_ilock(ip, iolock);

        ret = xfs_file_aio_write_checks(file, &pos, &count, &iolock);
        if (ret)
                goto out;

        /* We can write back this queue in page reclaim */
        current->backing_dev_info = mapping->backing_dev_info;

write_retry:
        trace_xfs_file_buffered_write(ip, count, iocb->ki_pos, 0);
        ret = generic_file_buffered_write(iocb, iovp, nr_segs,
                        pos, &iocb->ki_pos, count, ret);
        /*
         * if we just got an ENOSPC, flush the inode now we aren't holding any
         * page locks and retry *once*
         */
        if (ret == -ENOSPC && !enospc) {
                enospc = 1;
                ret = -xfs_flush_pages(ip, 0, -1, 0, FI_NONE);
                if (!ret)
                        goto write_retry;
        }

        current->backing_dev_info = NULL;
out:
        xfs_rw_iunlock(ip, iolock);
        return ret;
}

STATIC ssize_t
xfs_file_aio_write(
        struct kiocb            *iocb,
        const struct iovec      *iovp,
        unsigned long           nr_segs,
        loff_t                  pos)
{
        struct file             *file = iocb->ki_filp;
        struct address_space    *mapping = file->f_mapping;
        struct inode            *inode = mapping->host;
        struct xfs_inode        *ip = XFS_I(inode);
        ssize_t                 ret;
        size_t                  ocount = 0;

        XFS_STATS_INC(xs_write_calls);

        BUG_ON(iocb->ki_pos != pos);

        ret = generic_segment_checks(iovp, &nr_segs, &ocount, VERIFY_READ);
        if (ret)
                return ret;

        if (ocount == 0)
                return 0;

        xfs_wait_for_freeze(ip->i_mount, SB_FREEZE_WRITE);

        if (XFS_FORCED_SHUTDOWN(ip->i_mount))
                return -EIO;

        if (unlikely(file->f_flags & O_DIRECT))
                ret = xfs_file_dio_aio_write(iocb, iovp, nr_segs, pos, ocount);
        else
                ret = xfs_file_buffered_aio_write(iocb, iovp, nr_segs, pos,
                                                  ocount);

        if (ret > 0) {
                ssize_t err;

                XFS_STATS_ADD(xs_write_bytes, ret);

                /* Handle various SYNC-type writes */
                err = generic_write_sync(file, pos, ret);
                if (err < 0)
                        ret = err;
        }

        return ret;
}

STATIC long
xfs_file_fallocate(
        struct file     *file,
        int             mode,
        loff_t          offset,
        loff_t          len)
{
        struct inode    *inode = file->f_path.dentry->d_inode;
        long            error;
        loff_t          new_size = 0;
        xfs_flock64_t   bf;
        xfs_inode_t     *ip = XFS_I(inode);
        int             cmd = XFS_IOC_RESVSP;
        int             attr_flags = XFS_ATTR_NOLOCK;

        if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
                return -EOPNOTSUPP;

        bf.l_whence = 0;
        bf.l_start = offset;
        bf.l_len = len;

        xfs_ilock(ip, XFS_IOLOCK_EXCL);

        if (mode & FALLOC_FL_PUNCH_HOLE)
                cmd = XFS_IOC_UNRESVSP;

        /* check the new inode size is valid before allocating */
        if (!(mode & FALLOC_FL_KEEP_SIZE) &&
            offset + len > i_size_read(inode)) {
                new_size = offset + len;
                error = inode_newsize_ok(inode, new_size);
                if (error)
                        goto out_unlock;
        }

        if (file->f_flags & O_DSYNC)
                attr_flags |= XFS_ATTR_SYNC;

        error = -xfs_change_file_space(ip, cmd, &bf, 0, attr_flags);
        if (error)
                goto out_unlock;

        /* Change file size if needed */
        if (new_size) {
                struct iattr iattr;

                iattr.ia_valid = ATTR_SIZE;
                iattr.ia_size = new_size;
                error = -xfs_setattr_size(ip, &iattr, XFS_ATTR_NOLOCK);
        }

out_unlock:
        xfs_iunlock(ip, XFS_IOLOCK_EXCL);
        return error;
}


STATIC int
xfs_file_open(
        struct inode    *inode,
        struct file     *file)
{
        if (!(file->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
                return -EFBIG;
        if (XFS_FORCED_SHUTDOWN(XFS_M(inode->i_sb)))
                return -EIO;
        return 0;
}

STATIC int
xfs_dir_open(
        struct inode    *inode,
        struct file     *file)
{
        struct xfs_inode *ip = XFS_I(inode);
        int             mode;
        int             error;

        error = xfs_file_open(inode, file);
        if (error)
                return error;

        /*
         * If there are any blocks, read-ahead block 0 as we're almost
         * certain to have the next operation be a read there.
         */
        mode = xfs_ilock_map_shared(ip);
        if (ip->i_d.di_nextents > 0)
                xfs_da_reada_buf(NULL, ip, 0, XFS_DATA_FORK);
        xfs_iunlock(ip, mode);
        return 0;
}

STATIC int
xfs_file_release(
        struct inode    *inode,
        struct file     *filp)
{
        return -xfs_release(XFS_I(inode));
}

STATIC int
xfs_file_readdir(
        struct file     *filp,
        void            *dirent,
        filldir_t       filldir)
{
        struct inode    *inode = filp->f_path.dentry->d_inode;
        xfs_inode_t     *ip = XFS_I(inode);
        int             error;
        size_t          bufsize;

        /*
         * The Linux API doesn't pass down the total size of the buffer
         * we read into down to the filesystem.  With the filldir concept
         * it's not needed for correct information, but the XFS dir2 leaf
         * code wants an estimate of the buffer size to calculate it's
         * readahead window and size the buffers used for mapping to
         * physical blocks.
         *
         * Try to give it an estimate that's good enough, maybe at some
         * point we can change the ->readdir prototype to include the
         * buffer size.  For now we use the current glibc buffer size.
         */
        bufsize = (size_t)min_t(loff_t, 32768, ip->i_d.di_size);

        error = xfs_readdir(ip, dirent, bufsize,
                                (xfs_off_t *)&filp->f_pos, filldir);
        if (error)
                return -error;
        return 0;
}

STATIC int
xfs_file_mmap(
        struct file     *filp,
        struct vm_area_struct *vma)
{
        vma->vm_ops = &xfs_file_vm_ops;
        vma->vm_flags |= VM_CAN_NONLINEAR;

        file_accessed(filp);
        return 0;
}

/*
 * mmap()d file has taken write protection fault and is being made
 * writable. We can set the page state up correctly for a writable
 * page, which means we can do correct delalloc accounting (ENOSPC
 * checking!) and unwritten extent mapping.
 */
STATIC int
xfs_vm_page_mkwrite(
        struct vm_area_struct   *vma,
        struct vm_fault         *vmf)
{
        return block_page_mkwrite(vma, vmf, xfs_get_blocks);
}

const struct file_operations xfs_file_operations = {
        .llseek         = generic_file_llseek,
        .read           = do_sync_read,
        .write          = do_sync_write,
        .aio_read       = xfs_file_aio_read,
        .aio_write      = xfs_file_aio_write,
        .splice_read    = xfs_file_splice_read,
        .splice_write   = xfs_file_splice_write,
        .unlocked_ioctl = xfs_file_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = xfs_file_compat_ioctl,
#endif
        .mmap           = xfs_file_mmap,
        .open           = xfs_file_open,
        .release        = xfs_file_release,
        .fsync          = xfs_file_fsync,
        .fallocate      = xfs_file_fallocate,
};

const struct file_operations xfs_dir_file_operations = {
        .open           = xfs_dir_open,
        .read           = generic_read_dir,
        .readdir        = xfs_file_readdir,
        .llseek         = generic_file_llseek,
        .unlocked_ioctl = xfs_file_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = xfs_file_compat_ioctl,
#endif
        .fsync          = xfs_dir_fsync,
};

static const struct vm_operations_struct xfs_file_vm_ops = {
        .fault          = filemap_fault,
        .page_mkwrite   = xfs_vm_page_mkwrite,
};