[CONNECTOR]: Replace delayed work with usual work queue.

[linux-2.6/verdex.git] / fs / xfs / linux-2.6 / xfs_lrw.c

/*
 * Copyright (c) 2000-2003,2005 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_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_alloc.h"
#include "xfs_dmapi.h"
#include "xfs_quota.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_bmap.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_rtalloc.h"
#include "xfs_error.h"
#include "xfs_itable.h"
#include "xfs_rw.h"
#include "xfs_acl.h"
#include "xfs_cap.h"
#include "xfs_mac.h"
#include "xfs_attr.h"
#include "xfs_inode_item.h"
#include "xfs_buf_item.h"
#include "xfs_utils.h"
#include "xfs_iomap.h"

#include <linux/capability.h>
#include <linux/writeback.h>


#if defined(XFS_RW_TRACE)
void
xfs_rw_enter_trace(
        int                     tag,
        xfs_iocore_t            *io,
        void                    *data,
        size_t                  segs,
        loff_t                  offset,
        int                     ioflags)
{
        xfs_inode_t     *ip = XFS_IO_INODE(io);

        if (ip->i_rwtrace == NULL)
                return;
        ktrace_enter(ip->i_rwtrace,
                (void *)(unsigned long)tag,
                (void *)ip,
                (void *)((unsigned long)((ip->i_d.di_size >> 32) & 0xffffffff)),
                (void *)((unsigned long)(ip->i_d.di_size & 0xffffffff)),
                (void *)data,
                (void *)((unsigned long)segs),
                (void *)((unsigned long)((offset >> 32) & 0xffffffff)),
                (void *)((unsigned long)(offset & 0xffffffff)),
                (void *)((unsigned long)ioflags),
                (void *)((unsigned long)((io->io_new_size >> 32) & 0xffffffff)),
                (void *)((unsigned long)(io->io_new_size & 0xffffffff)),
                (void *)((unsigned long)current_pid()),
                (void *)NULL,
                (void *)NULL,
                (void *)NULL,
                (void *)NULL);
}

void
xfs_inval_cached_trace(
        xfs_iocore_t    *io,
        xfs_off_t       offset,
        xfs_off_t       len,
        xfs_off_t       first,
        xfs_off_t       last)
{
        xfs_inode_t     *ip = XFS_IO_INODE(io);

        if (ip->i_rwtrace == NULL)
                return;
        ktrace_enter(ip->i_rwtrace,
                (void *)(__psint_t)XFS_INVAL_CACHED,
                (void *)ip,
                (void *)((unsigned long)((offset >> 32) & 0xffffffff)),
                (void *)((unsigned long)(offset & 0xffffffff)),
                (void *)((unsigned long)((len >> 32) & 0xffffffff)),
                (void *)((unsigned long)(len & 0xffffffff)),
                (void *)((unsigned long)((first >> 32) & 0xffffffff)),
                (void *)((unsigned long)(first & 0xffffffff)),
                (void *)((unsigned long)((last >> 32) & 0xffffffff)),
                (void *)((unsigned long)(last & 0xffffffff)),
                (void *)((unsigned long)current_pid()),
                (void *)NULL,
                (void *)NULL,
                (void *)NULL,
                (void *)NULL,
                (void *)NULL);
}
#endif

/*
 *      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 inode            *ip,    /* inode                        */
        loff_t                  pos,    /* offset in file               */
        size_t                  count,  /* size of data to zero         */
        loff_t                  end_size)       /* max file size to set */
{
        unsigned                bytes;
        struct page             *page;
        struct address_space    *mapping;
        char                    *kaddr;
        int                     status;

        mapping = ip->i_mapping;
        do {
                unsigned long index, offset;

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

                status = -ENOMEM;
                page = grab_cache_page(mapping, index);
                if (!page)
                        break;

                kaddr = kmap(page);
                status = mapping->a_ops->prepare_write(NULL, page, offset,
                                                        offset + bytes);
                if (status) {
                        goto unlock;
                }

                memset((void *) (kaddr + offset), 0, bytes);
                flush_dcache_page(page);
                status = mapping->a_ops->commit_write(NULL, page, offset,
                                                        offset + bytes);
                if (!status) {
                        pos += bytes;
                        count -= bytes;
                        if (pos > i_size_read(ip))
                                i_size_write(ip, pos < end_size ? pos : end_size);
                }

unlock:
                kunmap(page);
                unlock_page(page);
                page_cache_release(page);
                if (status)
                        break;
        } while (count);

        return (-status);
}

ssize_t                 /* bytes read, or (-)  error */
xfs_read(
        bhv_desc_t              *bdp,
        struct kiocb            *iocb,
        const struct iovec      *iovp,
        unsigned int            segs,
        loff_t                  *offset,
        int                     ioflags,
        cred_t                  *credp)
{
        struct file             *file = iocb->ki_filp;
        struct inode            *inode = file->f_mapping->host;
        size_t                  size = 0;
        ssize_t                 ret;
        xfs_fsize_t             n;
        xfs_inode_t             *ip;
        xfs_mount_t             *mp;
        bhv_vnode_t             *vp;
        unsigned long           seg;

        ip = XFS_BHVTOI(bdp);
        vp = BHV_TO_VNODE(bdp);
        mp = ip->i_mount;

        XFS_STATS_INC(xs_read_calls);

        /* START copy & waste from filemap.c */
        for (seg = 0; seg < 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 =
                        (ip->i_d.di_flags & XFS_DIFLAG_REALTIME) ?
                                mp->m_rtdev_targp : mp->m_ddev_targp;
                if ((*offset & target->bt_smask) ||
                    (size & target->bt_smask)) {
                        if (*offset == ip->i_d.di_size) {
                                return (0);
                        }
                        return -XFS_ERROR(EINVAL);
                }
        }

        n = XFS_MAXIOFFSET(mp) - *offset;
        if ((n <= 0) || (size == 0))
                return 0;

        if (n < size)
                size = n;

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        if (unlikely(ioflags & IO_ISDIRECT))
                mutex_lock(&inode->i_mutex);
        xfs_ilock(ip, XFS_IOLOCK_SHARED);

        if (DM_EVENT_ENABLED(vp->v_vfsp, ip, DM_EVENT_READ) &&
            !(ioflags & IO_INVIS)) {
                bhv_vrwlock_t locktype = VRWLOCK_READ;
                int dmflags = FILP_DELAY_FLAG(file) | DM_SEM_FLAG_RD(ioflags);

                ret = -XFS_SEND_DATA(mp, DM_EVENT_READ,
                                        BHV_TO_VNODE(bdp), *offset, size,
                                        dmflags, &locktype);
                if (ret) {
                        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
                        if (unlikely(ioflags & IO_ISDIRECT))
                                mutex_unlock(&inode->i_mutex);
                        return ret;
                }
        }

        if (unlikely(ioflags & IO_ISDIRECT)) {
                if (VN_CACHED(vp))
                        bhv_vop_flushinval_pages(vp, ctooff(offtoct(*offset)),
                                                 -1, FI_REMAPF_LOCKED);
                mutex_unlock(&inode->i_mutex);
        }

        xfs_rw_enter_trace(XFS_READ_ENTER, &ip->i_iocore,
                                (void *)iovp, segs, *offset, ioflags);

        iocb->ki_pos = *offset;
        ret = generic_file_aio_read(iocb, iovp, segs, *offset);
        if (ret == -EIOCBQUEUED && !(ioflags & IO_ISAIO))
                ret = wait_on_sync_kiocb(iocb);
        if (ret > 0)
                XFS_STATS_ADD(xs_read_bytes, ret);

        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
        return ret;
}

ssize_t
xfs_sendfile(
        bhv_desc_t              *bdp,
        struct file             *filp,
        loff_t                  *offset,
        int                     ioflags,
        size_t                  count,
        read_actor_t            actor,
        void                    *target,
        cred_t                  *credp)
{
        xfs_inode_t             *ip = XFS_BHVTOI(bdp);
        xfs_mount_t             *mp = ip->i_mount;
        ssize_t                 ret;

        XFS_STATS_INC(xs_read_calls);
        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        xfs_ilock(ip, XFS_IOLOCK_SHARED);

        if (DM_EVENT_ENABLED(BHV_TO_VNODE(bdp)->v_vfsp, ip, DM_EVENT_READ) &&
            (!(ioflags & IO_INVIS))) {
                bhv_vrwlock_t locktype = VRWLOCK_READ;
                int error;

                error = XFS_SEND_DATA(mp, DM_EVENT_READ, BHV_TO_VNODE(bdp),
                                      *offset, count,
                                      FILP_DELAY_FLAG(filp), &locktype);
                if (error) {
                        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
                        return -error;
                }
        }
        xfs_rw_enter_trace(XFS_SENDFILE_ENTER, &ip->i_iocore,
                   (void *)(unsigned long)target, count, *offset, ioflags);
        ret = generic_file_sendfile(filp, offset, count, actor, target);
        if (ret > 0)
                XFS_STATS_ADD(xs_read_bytes, ret);

        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
        return ret;
}

ssize_t
xfs_splice_read(
        bhv_desc_t              *bdp,
        struct file             *infilp,
        loff_t                  *ppos,
        struct pipe_inode_info  *pipe,
        size_t                  count,
        int                     flags,
        int                     ioflags,
        cred_t                  *credp)
{
        xfs_inode_t             *ip = XFS_BHVTOI(bdp);
        xfs_mount_t             *mp = ip->i_mount;
        ssize_t                 ret;

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

        xfs_ilock(ip, XFS_IOLOCK_SHARED);

        if (DM_EVENT_ENABLED(BHV_TO_VNODE(bdp)->v_vfsp, ip, DM_EVENT_READ) &&
            (!(ioflags & IO_INVIS))) {
                bhv_vrwlock_t locktype = VRWLOCK_READ;
                int error;

                error = XFS_SEND_DATA(mp, DM_EVENT_READ, BHV_TO_VNODE(bdp),
                                        *ppos, count,
                                        FILP_DELAY_FLAG(infilp), &locktype);
                if (error) {
                        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
                        return -error;
                }
        }
        xfs_rw_enter_trace(XFS_SPLICE_READ_ENTER, &ip->i_iocore,
                           pipe, count, *ppos, ioflags);
        ret = generic_file_splice_read(infilp, ppos, pipe, count, flags);
        if (ret > 0)
                XFS_STATS_ADD(xs_read_bytes, ret);

        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
        return ret;
}

ssize_t
xfs_splice_write(
        bhv_desc_t              *bdp,
        struct pipe_inode_info  *pipe,
        struct file             *outfilp,
        loff_t                  *ppos,
        size_t                  count,
        int                     flags,
        int                     ioflags,
        cred_t                  *credp)
{
        xfs_inode_t             *ip = XFS_BHVTOI(bdp);
        xfs_mount_t             *mp = ip->i_mount;
        ssize_t                 ret;
        struct inode            *inode = outfilp->f_mapping->host;
        xfs_fsize_t             isize;

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

        xfs_ilock(ip, XFS_IOLOCK_EXCL);

        if (DM_EVENT_ENABLED(BHV_TO_VNODE(bdp)->v_vfsp, ip, DM_EVENT_WRITE) &&
            (!(ioflags & IO_INVIS))) {
                bhv_vrwlock_t locktype = VRWLOCK_WRITE;
                int error;

                error = XFS_SEND_DATA(mp, DM_EVENT_WRITE, BHV_TO_VNODE(bdp),
                                        *ppos, count,
                                        FILP_DELAY_FLAG(outfilp), &locktype);
                if (error) {
                        xfs_iunlock(ip, XFS_IOLOCK_EXCL);
                        return -error;
                }
        }
        xfs_rw_enter_trace(XFS_SPLICE_WRITE_ENTER, &ip->i_iocore,
                           pipe, count, *ppos, ioflags);
        ret = generic_file_splice_write(pipe, outfilp, ppos, count, flags);
        if (ret > 0)
                XFS_STATS_ADD(xs_write_bytes, ret);

        isize = i_size_read(inode);
        if (unlikely(ret < 0 && ret != -EFAULT && *ppos > isize))
                *ppos = isize;

        if (*ppos > ip->i_d.di_size) {
                xfs_ilock(ip, XFS_ILOCK_EXCL);
                if (*ppos > ip->i_d.di_size) {
                        ip->i_d.di_size = *ppos;
                        i_size_write(inode, *ppos);
                        ip->i_update_core = 1;
                        ip->i_update_size = 1;
                }
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
        }
        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(
        struct inode    *ip,
        xfs_iocore_t    *io,
        xfs_fsize_t     isize,
        xfs_fsize_t     end_size)
{
        xfs_fileoff_t   last_fsb;
        xfs_mount_t     *mp = io->io_mount;
        int             nimaps;
        int             zero_offset;
        int             zero_len;
        int             error = 0;
        xfs_bmbt_irec_t imap;
        loff_t          loff;

        ASSERT(ismrlocked(io->io_lock, MR_UPDATE) != 0);

        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(mp, NULL, io, last_fsb, 1, 0, NULL, 0, &imap,
                          &nimaps, NULL, NULL);
        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(mp, io, XFS_ILOCK_EXCL| XFS_EXTSIZE_RD);

        loff = XFS_FSB_TO_B(mp, last_fsb);
        zero_len = mp->m_sb.sb_blocksize - zero_offset;
        error = xfs_iozero(ip, loff + zero_offset, zero_len, end_size);

        XFS_ILOCK(mp, io, XFS_ILOCK_EXCL|XFS_EXTSIZE_RD);
        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(
        bhv_vnode_t     *vp,
        xfs_iocore_t    *io,
        xfs_off_t       offset,         /* starting I/O offset */
        xfs_fsize_t     isize,          /* current inode size */
        xfs_fsize_t     end_size)       /* terminal inode size */
{
        struct inode    *ip = vn_to_inode(vp);
        xfs_fileoff_t   start_zero_fsb;
        xfs_fileoff_t   end_zero_fsb;
        xfs_fileoff_t   zero_count_fsb;
        xfs_fileoff_t   last_fsb;
        xfs_mount_t     *mp = io->io_mount;
        int             nimaps;
        int             error = 0;
        xfs_bmbt_irec_t imap;

        ASSERT(ismrlocked(io->io_lock, MR_UPDATE));
        ASSERT(ismrlocked(io->io_iolock, MR_UPDATE));
        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, io, isize, end_size);
        if (error) {
                ASSERT(ismrlocked(io->io_lock, MR_UPDATE));
                ASSERT(ismrlocked(io->io_iolock, MR_UPDATE));
                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(mp, NULL, io, start_zero_fsb, zero_count_fsb,
                                  0, NULL, 0, &imap, &nimaps, NULL, NULL);
                if (error) {
                        ASSERT(ismrlocked(io->io_lock, MR_UPDATE));
                        ASSERT(ismrlocked(io->io_iolock, MR_UPDATE));
                        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(mp, io, XFS_ILOCK_EXCL|XFS_EXTSIZE_RD);

                error = xfs_iozero(ip,
                                   XFS_FSB_TO_B(mp, start_zero_fsb),
                                   XFS_FSB_TO_B(mp, imap.br_blockcount),
                                   end_size);
                if (error) {
                        goto out_lock;
                }

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

                XFS_ILOCK(mp, io, XFS_ILOCK_EXCL|XFS_EXTSIZE_RD);
        }

        return 0;

out_lock:

        XFS_ILOCK(mp, io, XFS_ILOCK_EXCL|XFS_EXTSIZE_RD);
        ASSERT(error >= 0);
        return error;
}

ssize_t                         /* bytes written, or (-) error */
xfs_write(
        bhv_desc_t              *bdp,
        struct kiocb            *iocb,
        const struct iovec      *iovp,
        unsigned int            nsegs,
        loff_t                  *offset,
        int                     ioflags,
        cred_t                  *credp)
{
        struct file             *file = iocb->ki_filp;
        struct address_space    *mapping = file->f_mapping;
        struct inode            *inode = mapping->host;
        unsigned long           segs = nsegs;
        xfs_inode_t             *xip;
        xfs_mount_t             *mp;
        ssize_t                 ret = 0, error = 0;
        xfs_fsize_t             isize, new_size;
        xfs_iocore_t            *io;
        bhv_vnode_t             *vp;
        unsigned long           seg;
        int                     iolock;
        int                     eventsent = 0;
        bhv_vrwlock_t           locktype;
        size_t                  ocount = 0, count;
        loff_t                  pos;
        int                     need_i_mutex = 1, need_flush = 0;

        XFS_STATS_INC(xs_write_calls);

        vp = BHV_TO_VNODE(bdp);
        xip = XFS_BHVTOI(bdp);

        for (seg = 0; seg < 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.
                 */
                ocount += iv->iov_len;
                if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
                        return -EINVAL;
                if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
                        continue;
                if (seg == 0)
                        return -EFAULT;
                segs = seg;
                ocount -= iv->iov_len;  /* This segment is no good */
                break;
        }

        count = ocount;
        pos = *offset;

        if (count == 0)
                return 0;

        io = &xip->i_iocore;
        mp = io->io_mount;

        vfs_wait_for_freeze(vp->v_vfsp, SB_FREEZE_WRITE);

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        if (ioflags & IO_ISDIRECT) {
                xfs_buftarg_t   *target =
                        (xip->i_d.di_flags & XFS_DIFLAG_REALTIME) ?
                                mp->m_rtdev_targp : mp->m_ddev_targp;

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

                if (!VN_CACHED(vp) && pos < i_size_read(inode))
                        need_i_mutex = 0;

                if (VN_CACHED(vp))
                        need_flush = 1;
        }

relock:
        if (need_i_mutex) {
                iolock = XFS_IOLOCK_EXCL;
                locktype = VRWLOCK_WRITE;

                mutex_lock(&inode->i_mutex);
        } else {
                iolock = XFS_IOLOCK_SHARED;
                locktype = VRWLOCK_WRITE_DIRECT;
        }

        xfs_ilock(xip, XFS_ILOCK_EXCL|iolock);

        isize = i_size_read(inode);

        if (file->f_flags & O_APPEND)
                *offset = isize;

start:
        error = -generic_write_checks(file, &pos, &count,
                                        S_ISBLK(inode->i_mode));
        if (error) {
                xfs_iunlock(xip, XFS_ILOCK_EXCL|iolock);
                goto out_unlock_mutex;
        }

        new_size = pos + count;
        if (new_size > isize)
                io->io_new_size = new_size;

        if ((DM_EVENT_ENABLED(vp->v_vfsp, xip, DM_EVENT_WRITE) &&
            !(ioflags & IO_INVIS) && !eventsent)) {
                loff_t          savedsize = pos;
                int             dmflags = FILP_DELAY_FLAG(file);

                if (need_i_mutex)
                        dmflags |= DM_FLAGS_IMUX;

                xfs_iunlock(xip, XFS_ILOCK_EXCL);
                error = XFS_SEND_DATA(xip->i_mount, DM_EVENT_WRITE, vp,
                                      pos, count,
                                      dmflags, &locktype);
                if (error) {
                        xfs_iunlock(xip, iolock);
                        goto out_unlock_mutex;
                }
                xfs_ilock(xip, XFS_ILOCK_EXCL);
                eventsent = 1;

                /*
                 * The iolock was dropped and reacquired in XFS_SEND_DATA
                 * so we have to recheck the size when appending.
                 * We will only "goto start;" once, since having sent the
                 * event prevents another call to XFS_SEND_DATA, which is
                 * what allows the size to change in the first place.
                 */
                if ((file->f_flags & O_APPEND) && savedsize != isize) {
                        pos = isize = xip->i_d.di_size;
                        goto start;
                }
        }

        if (likely(!(ioflags & IO_INVIS))) {
                file_update_time(file);
                xfs_ichgtime_fast(xip, inode,
                                  XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
        }

        /*
         * If the offset is beyond the size of the file, we have a couple
         * of things to do. First, if there is already space allocated
         * we need to either create holes or zero the disk or ...
         *
         * If there is a page where the previous size lands, we need
         * to zero it out up to the new size.
         */

        if (pos > isize) {
                error = xfs_zero_eof(BHV_TO_VNODE(bdp), io, pos,
                                        isize, pos + count);
                if (error) {
                        xfs_iunlock(xip, XFS_ILOCK_EXCL|iolock);
                        goto out_unlock_mutex;
                }
        }
        xfs_iunlock(xip, XFS_ILOCK_EXCL);

        /*
         * 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.
         */

        if (((xip->i_d.di_mode & S_ISUID) ||
            ((xip->i_d.di_mode & (S_ISGID | S_IXGRP)) ==
                (S_ISGID | S_IXGRP))) &&
             !capable(CAP_FSETID)) {
                error = xfs_write_clear_setuid(xip);
                if (likely(!error))
                        error = -remove_suid(file->f_path.dentry);
                if (unlikely(error)) {
                        xfs_iunlock(xip, iolock);
                        goto out_unlock_mutex;
                }
        }

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

        if ((ioflags & IO_ISDIRECT)) {
                if (need_flush) {
                        xfs_inval_cached_trace(io, pos, -1,
                                        ctooff(offtoct(pos)), -1);
                        bhv_vop_flushinval_pages(vp, ctooff(offtoct(pos)),
                                        -1, FI_REMAPF_LOCKED);
                }

                if (need_i_mutex) {
                        /* demote the lock now the cached pages are gone */
                        XFS_ILOCK_DEMOTE(mp, io, XFS_IOLOCK_EXCL);
                        mutex_unlock(&inode->i_mutex);

                        iolock = XFS_IOLOCK_SHARED;
                        locktype = VRWLOCK_WRITE_DIRECT;
                        need_i_mutex = 0;
                }

                xfs_rw_enter_trace(XFS_DIOWR_ENTER, io, (void *)iovp, segs,
                                *offset, ioflags);
                ret = generic_file_direct_write(iocb, iovp,
                                &segs, pos, offset, count, ocount);

                /*
                 * direct-io write to a hole: fall through to buffered I/O
                 * for completing the rest of the request.
                 */
                if (ret >= 0 && ret != count) {
                        XFS_STATS_ADD(xs_write_bytes, ret);

                        pos += ret;
                        count -= ret;

                        need_i_mutex = 1;
                        ioflags &= ~IO_ISDIRECT;
                        xfs_iunlock(xip, iolock);
                        goto relock;
                }
        } else {
                xfs_rw_enter_trace(XFS_WRITE_ENTER, io, (void *)iovp, segs,
                                *offset, ioflags);
                ret = generic_file_buffered_write(iocb, iovp, segs,
                                pos, offset, count, ret);
        }

        current->backing_dev_info = NULL;

        if (ret == -EIOCBQUEUED && !(ioflags & IO_ISAIO))
                ret = wait_on_sync_kiocb(iocb);

        if ((ret == -ENOSPC) &&
            DM_EVENT_ENABLED(vp->v_vfsp, xip, DM_EVENT_NOSPACE) &&
            !(ioflags & IO_INVIS)) {

                xfs_rwunlock(bdp, locktype);
                if (need_i_mutex)
                        mutex_unlock(&inode->i_mutex);
                error = XFS_SEND_NAMESP(xip->i_mount, DM_EVENT_NOSPACE, vp,
                                DM_RIGHT_NULL, vp, DM_RIGHT_NULL, NULL, NULL,
                                0, 0, 0); /* Delay flag intentionally  unused */
                if (error)
                        goto out_nounlocks;
                if (need_i_mutex)
                        mutex_lock(&inode->i_mutex);
                xfs_rwlock(bdp, locktype);
                pos = xip->i_d.di_size;
                ret = 0;
                goto retry;
        }

        isize = i_size_read(inode);
        if (unlikely(ret < 0 && ret != -EFAULT && *offset > isize))
                *offset = isize;

        if (*offset > xip->i_d.di_size) {
                xfs_ilock(xip, XFS_ILOCK_EXCL);
                if (*offset > xip->i_d.di_size) {
                        xip->i_d.di_size = *offset;
                        i_size_write(inode, *offset);
                        xip->i_update_core = 1;
                        xip->i_update_size = 1;
                }
                xfs_iunlock(xip, XFS_ILOCK_EXCL);
        }

        error = -ret;
        if (ret <= 0)
                goto out_unlock_internal;

        XFS_STATS_ADD(xs_write_bytes, ret);

        /* Handle various SYNC-type writes */
        if ((file->f_flags & O_SYNC) || IS_SYNC(inode)) {
                error = xfs_write_sync_logforce(mp, xip);
                if (error)
                        goto out_unlock_internal;

                xfs_rwunlock(bdp, locktype);
                if (need_i_mutex)
                        mutex_unlock(&inode->i_mutex);

                error = sync_page_range(inode, mapping, pos, ret);
                if (!error)
                        error = ret;
                return error;
        }

 out_unlock_internal:
        xfs_rwunlock(bdp, locktype);
 out_unlock_mutex:
        if (need_i_mutex)
                mutex_unlock(&inode->i_mutex);
 out_nounlocks:
        return -error;
}

/*
 * All xfs metadata buffers except log state machine buffers
 * get this attached as their b_bdstrat callback function.
 * This is so that we can catch a buffer
 * after prematurely unpinning it to forcibly shutdown the filesystem.
 */
int
xfs_bdstrat_cb(struct xfs_buf *bp)
{
        xfs_mount_t     *mp;

        mp = XFS_BUF_FSPRIVATE3(bp, xfs_mount_t *);
        if (!XFS_FORCED_SHUTDOWN(mp)) {
                xfs_buf_iorequest(bp);
                return 0;
        } else {
                xfs_buftrace("XFS__BDSTRAT IOERROR", bp);
                /*
                 * Metadata write that didn't get logged but
                 * written delayed anyway. These aren't associated
                 * with a transaction, and can be ignored.
                 */
                if (XFS_BUF_IODONE_FUNC(bp) == NULL &&
                    (XFS_BUF_ISREAD(bp)) == 0)
                        return (xfs_bioerror_relse(bp));
                else
                        return (xfs_bioerror(bp));
        }
}


int
xfs_bmap(bhv_desc_t     *bdp,
        xfs_off_t       offset,
        ssize_t         count,
        int             flags,
        xfs_iomap_t     *iomapp,
        int             *niomaps)
{
        xfs_inode_t     *ip = XFS_BHVTOI(bdp);
        xfs_iocore_t    *io = &ip->i_iocore;

        ASSERT((ip->i_d.di_mode & S_IFMT) == S_IFREG);
        ASSERT(((ip->i_d.di_flags & XFS_DIFLAG_REALTIME) != 0) ==
               ((ip->i_iocore.io_flags & XFS_IOCORE_RT) != 0));

        return xfs_iomap(io, offset, count, flags, iomapp, niomaps);
}

/*
 * Wrapper around bdstrat so that we can stop data
 * from going to disk in case we are shutting down the filesystem.
 * Typically user data goes thru this path; one of the exceptions
 * is the superblock.
 */
int
xfsbdstrat(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp)
{
        ASSERT(mp);
        if (!XFS_FORCED_SHUTDOWN(mp)) {
                /* Grio redirection would go here
                 * if (XFS_BUF_IS_GRIO(bp)) {
                 */

                xfs_buf_iorequest(bp);
                return 0;
        }

        xfs_buftrace("XFSBDSTRAT IOERROR", bp);
        return (xfs_bioerror_relse(bp));
}

/*
 * If the underlying (data/log/rt) device is readonly, there are some
 * operations that cannot proceed.
 */
int
xfs_dev_is_read_only(
        xfs_mount_t             *mp,
        char                    *message)
{
        if (xfs_readonly_buftarg(mp->m_ddev_targp) ||
            xfs_readonly_buftarg(mp->m_logdev_targp) ||
            (mp->m_rtdev_targp && xfs_readonly_buftarg(mp->m_rtdev_targp))) {
                cmn_err(CE_NOTE,
                        "XFS: %s required on read-only device.", message);
                cmn_err(CE_NOTE,
                        "XFS: write access unavailable, cannot proceed.");
                return EROFS;
        }
        return 0;
}