affs: do not zero ->i_op

[linux/fpc-iii.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_attr.h"
#include "xfs_inode_item.h"
#include "xfs_buf_item.h"
#include "xfs_utils.h"
#include "xfs_iomap.h"
#include "xfs_vnodeops.h"

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


#if defined(XFS_RW_TRACE)
void
xfs_rw_enter_trace(
        int                     tag,
        xfs_inode_t             *ip,
        void                    *data,
        size_t                  segs,
        loff_t                  offset,
        int                     ioflags)
{
        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)((ip->i_new_size >> 32) & 0xffffffff)),
                (void *)((unsigned long)(ip->i_new_size & 0xffffffff)),
                (void *)((unsigned long)current_pid()),
                (void *)NULL,
                (void *)NULL,
                (void *)NULL,
                (void *)NULL);
}

void
xfs_inval_cached_trace(
        xfs_inode_t     *ip,
        xfs_off_t       offset,
        xfs_off_t       len,
        xfs_off_t       first,
        xfs_off_t       last)
{

        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 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);
}

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


        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 =
                        XFS_IS_REALTIME_INODE(ip) ?
                                mp->m_rtdev_targp : mp->m_ddev_targp;
                if ((*offset & target->bt_smask) ||
                    (size & target->bt_smask)) {
                        if (*offset == ip->i_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(ip, DM_EVENT_READ) && !(ioflags & IO_INVIS)) {
                int dmflags = FILP_DELAY_FLAG(file) | DM_SEM_FLAG_RD(ioflags);
                int iolock = XFS_IOLOCK_SHARED;

                ret = -XFS_SEND_DATA(mp, DM_EVENT_READ, ip, *offset, size,
                                        dmflags, &iolock);
                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 (inode->i_mapping->nrpages)
                        ret = -xfs_flushinval_pages(ip, (*offset & PAGE_CACHE_MASK),
                                                    -1, FI_REMAPF_LOCKED);
                mutex_unlock(&inode->i_mutex);
                if (ret) {
                        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
                        return ret;
                }
        }

        xfs_rw_enter_trace(XFS_READ_ENTER, ip,
                                (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_splice_read(
        xfs_inode_t             *ip,
        struct file             *infilp,
        loff_t                  *ppos,
        struct pipe_inode_info  *pipe,
        size_t                  count,
        int                     flags,
        int                     ioflags)
{
        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(ip, DM_EVENT_READ) && !(ioflags & IO_INVIS)) {
                int iolock = XFS_IOLOCK_SHARED;
                int error;

                error = XFS_SEND_DATA(mp, DM_EVENT_READ, ip, *ppos, count,
                                        FILP_DELAY_FLAG(infilp), &iolock);
                if (error) {
                        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
                        return -error;
                }
        }
        xfs_rw_enter_trace(XFS_SPLICE_READ_ENTER, ip,
                           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(
        xfs_inode_t             *ip,
        struct pipe_inode_info  *pipe,
        struct file             *outfilp,
        loff_t                  *ppos,
        size_t                  count,
        int                     flags,
        int                     ioflags)
{
        xfs_mount_t             *mp = ip->i_mount;
        ssize_t                 ret;
        struct inode            *inode = outfilp->f_mapping->host;
        xfs_fsize_t             isize, new_size;

        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(ip, DM_EVENT_WRITE) && !(ioflags & IO_INVIS)) {
                int iolock = XFS_IOLOCK_EXCL;
                int error;

                error = XFS_SEND_DATA(mp, DM_EVENT_WRITE, ip, *ppos, count,
                                        FILP_DELAY_FLAG(outfilp), &iolock);
                if (error) {
                        xfs_iunlock(ip, XFS_IOLOCK_EXCL);
                        return -error;
                }
        }

        new_size = *ppos + count;

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        if (new_size > ip->i_size)
                ip->i_new_size = new_size;
        xfs_iunlock(ip, XFS_ILOCK_EXCL);

        xfs_rw_enter_trace(XFS_SPLICE_WRITE_ENTER, ip,
                           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_size) {
                xfs_ilock(ip, XFS_ILOCK_EXCL);
                if (*ppos > ip->i_size)
                        ip->i_size = *ppos;
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
        }

        if (ip->i_new_size) {
                xfs_ilock(ip, XFS_ILOCK_EXCL);
                ip->i_new_size = 0;
                if (ip->i_d.di_size > ip->i_size)
                        ip->i_d.di_size = ip->i_size;
                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(
        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(NULL, ip, 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(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(NULL, ip, start_zero_fsb, zero_count_fsb,
                                  0, NULL, 0, &imap, &nimaps, NULL, NULL);
                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;
}

ssize_t                         /* bytes written, or (-) error */
xfs_write(
        struct xfs_inode        *xip,
        struct kiocb            *iocb,
        const struct iovec      *iovp,
        unsigned int            nsegs,
        loff_t                  *offset,
        int                     ioflags)
{
        struct file             *file = iocb->ki_filp;
        struct address_space    *mapping = file->f_mapping;
        struct inode            *inode = mapping->host;
        unsigned long           segs = nsegs;
        xfs_mount_t             *mp;
        ssize_t                 ret = 0, error = 0;
        xfs_fsize_t             isize, new_size;
        int                     iolock;
        int                     eventsent = 0;
        size_t                  ocount = 0, count;
        loff_t                  pos;
        int                     need_i_mutex;

        XFS_STATS_INC(xs_write_calls);

        error = generic_segment_checks(iovp, &segs, &ocount, VERIFY_READ);
        if (error)
                return error;

        count = ocount;
        pos = *offset;

        if (count == 0)
                return 0;

        mp = xip->i_mount;

        xfs_wait_for_freeze(mp, SB_FREEZE_WRITE);

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

relock:
        if (ioflags & IO_ISDIRECT) {
                iolock = XFS_IOLOCK_SHARED;
                need_i_mutex = 0;
        } else {
                iolock = XFS_IOLOCK_EXCL;
                need_i_mutex = 1;
                mutex_lock(&inode->i_mutex);
        }

        xfs_ilock(xip, XFS_ILOCK_EXCL|iolock);

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;
        }

        if ((DM_EVENT_ENABLED(xip, DM_EVENT_WRITE) &&
            !(ioflags & IO_INVIS) && !eventsent)) {
                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, xip,
                                      pos, count, dmflags, &iolock);
                if (error) {
                        goto out_unlock_internal;
                }
                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) && pos != xip->i_size)
                        goto start;
        }

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

                if ((pos & target->bt_smask) || (count & target->bt_smask)) {
                        xfs_iunlock(xip, XFS_ILOCK_EXCL|iolock);
                        return XFS_ERROR(-EINVAL);
                }

                if (!need_i_mutex && (mapping->nrpages || pos > xip->i_size)) {
                        xfs_iunlock(xip, XFS_ILOCK_EXCL|iolock);
                        iolock = XFS_IOLOCK_EXCL;
                        need_i_mutex = 1;
                        mutex_lock(&inode->i_mutex);
                        xfs_ilock(xip, XFS_ILOCK_EXCL|iolock);
                        goto start;
                }
        }

        new_size = pos + count;
        if (new_size > xip->i_size)
                xip->i_new_size = new_size;

        if (likely(!(ioflags & IO_INVIS)))
                xfs_ichgtime(xip, 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 > xip->i_size) {
                error = xfs_zero_eof(xip, pos, xip->i_size);
                if (error) {
                        xfs_iunlock(xip, XFS_ILOCK_EXCL);
                        goto out_unlock_internal;
                }
        }
        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 = -file_remove_suid(file);
                if (unlikely(error)) {
                        goto out_unlock_internal;
                }
        }

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

        if ((ioflags & IO_ISDIRECT)) {
                if (mapping->nrpages) {
                        WARN_ON(need_i_mutex == 0);
                        xfs_inval_cached_trace(xip, pos, -1,
                                        (pos & PAGE_CACHE_MASK), -1);
                        error = xfs_flushinval_pages(xip,
                                        (pos & PAGE_CACHE_MASK),
                                        -1, FI_REMAPF_LOCKED);
                        if (error)
                                goto out_unlock_internal;
                }

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

                        iolock = XFS_IOLOCK_SHARED;
                        need_i_mutex = 0;
                }

                xfs_rw_enter_trace(XFS_DIOWR_ENTER, xip, (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;

                        ioflags &= ~IO_ISDIRECT;
                        xfs_iunlock(xip, iolock);
                        goto relock;
                }
        } else {
                xfs_rw_enter_trace(XFS_WRITE_ENTER, xip, (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);

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

        if (*offset > xip->i_size) {
                xfs_ilock(xip, XFS_ILOCK_EXCL);
                if (*offset > xip->i_size)
                        xip->i_size = *offset;
                xfs_iunlock(xip, XFS_ILOCK_EXCL);
        }

        if (ret == -ENOSPC &&
            DM_EVENT_ENABLED(xip, DM_EVENT_NOSPACE) && !(ioflags & IO_INVIS)) {
                xfs_iunlock(xip, iolock);
                if (need_i_mutex)
                        mutex_unlock(&inode->i_mutex);
                error = XFS_SEND_NAMESP(xip->i_mount, DM_EVENT_NOSPACE, xip,
                                DM_RIGHT_NULL, xip, DM_RIGHT_NULL, NULL, NULL,
                                0, 0, 0); /* Delay flag intentionally  unused */
                if (need_i_mutex)
                        mutex_lock(&inode->i_mutex);
                xfs_ilock(xip, iolock);
                if (error)
                        goto out_unlock_internal;
                goto start;
        }

        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)) {
                int error2;

                xfs_iunlock(xip, iolock);
                if (need_i_mutex)
                        mutex_unlock(&inode->i_mutex);
                error2 = sync_page_range(inode, mapping, pos, ret);
                if (!error)
                        error = error2;
                if (need_i_mutex)
                        mutex_lock(&inode->i_mutex);
                xfs_ilock(xip, iolock);
                error2 = xfs_write_sync_logforce(mp, xip);
                if (!error)
                        error = error2;
        }

 out_unlock_internal:
        if (xip->i_new_size) {
                xfs_ilock(xip, XFS_ILOCK_EXCL);
                xip->i_new_size = 0;
                /*
                 * If this was a direct or synchronous I/O that failed (such
                 * as ENOSPC) then part of the I/O may have been written to
                 * disk before the error occured.  In this case the on-disk
                 * file size may have been adjusted beyond the in-memory file
                 * size and now needs to be truncated back.
                 */
                if (xip->i_d.di_size > xip->i_size)
                        xip->i_d.di_size = xip->i_size;
                xfs_iunlock(xip, XFS_ILOCK_EXCL);
        }
        xfs_iunlock(xip, iolock);
 out_unlock_mutex:
        if (need_i_mutex)
                mutex_unlock(&inode->i_mutex);
        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)
{
        if (XFS_FORCED_SHUTDOWN(bp->b_mount)) {
                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));
        }

        xfs_buf_iorequest(bp);
        return 0;
}

/*
 * 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.
 */
void
xfsbdstrat(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp)
{
        ASSERT(mp);
        if (!XFS_FORCED_SHUTDOWN(mp)) {
                xfs_buf_iorequest(bp);
                return;
        }

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