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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_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       */
{
      struct page       *page;
      struct address_space    *mapping;
      int               status;

      mapping = 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(page, offset, bytes, KM_USER0);

            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;
      bhv_vnode_t       *vp = XFS_ITOV(ip);
      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 =
                  (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_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)) {
            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, vp, *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))
                  ret = xfs_flushinval_pages(ip,
                              ctooff(offtoct(*offset)),
                              -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->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_splice_read(
      xfs_inode_t       *ip,
      struct file       *infilp,
      loff_t                  *ppos,
      struct pipe_inode_info  *pipe,
      size_t                  count,
      int               flags,
      int               ioflags)
{
      bhv_vnode_t       *vp = XFS_ITOV(ip);
      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)) {
            bhv_vrwlock_t locktype = VRWLOCK_READ;
            int error;

            error = XFS_SEND_DATA(mp, DM_EVENT_READ, vp, *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(
      xfs_inode_t       *ip,
      struct pipe_inode_info  *pipe,
      struct file       *outfilp,
      loff_t                  *ppos,
      size_t                  count,
      int               flags,
      int               ioflags)
{
      bhv_vnode_t       *vp = XFS_ITOV(ip);
      xfs_mount_t       *mp = ip->i_mount;
      xfs_iocore_t            *io = &ip->i_iocore;
      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)) {
            bhv_vrwlock_t locktype = VRWLOCK_WRITE;
            int error;

            error = XFS_SEND_DATA(mp, DM_EVENT_WRITE, vp, *ppos, count,
                              FILP_DELAY_FLAG(outfilp), &locktype);
            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)
            io->io_new_size = new_size;
      xfs_iunlock(ip, XFS_ILOCK_EXCL);

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

      if (io->io_new_size) {
            xfs_ilock(ip, XFS_ILOCK_EXCL);
            io->io_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(
      struct inode      *ip,
      xfs_iocore_t      *io,
      xfs_fsize_t offset,
      xfs_fsize_t isize)
{
      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;

      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);

      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(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 */
{
      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_fileoff_t     zero_off;
      xfs_fsize_t zero_len;
      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, offset, isize);
      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);

            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(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(
      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;
      bhv_vnode_t       *vp = XFS_ITOV(xip);
      unsigned long           segs = nsegs;
      xfs_mount_t       *mp;
      ssize_t                 ret = 0, error = 0;
      xfs_fsize_t       isize, new_size;
      xfs_iocore_t            *io;
      int               iolock;
      int               eventsent = 0;
      bhv_vrwlock_t           locktype;
      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;

      io = &xip->i_iocore;
      mp = io->io_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;
            locktype = VRWLOCK_WRITE_DIRECT;
            need_i_mutex = 0;
      } else {
            iolock = XFS_IOLOCK_EXCL;
            locktype = VRWLOCK_WRITE;
            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, vp,
                              pos, count,
                              dmflags, &locktype);
            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 =
                  (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)) {
                  xfs_iunlock(xip, XFS_ILOCK_EXCL|iolock);
                  return XFS_ERROR(-EINVAL);
            }

            if (!need_i_mutex && (VN_CACHED(vp) || pos > xip->i_size)) {
                  xfs_iunlock(xip, XFS_ILOCK_EXCL|iolock);
                  iolock = XFS_IOLOCK_EXCL;
                  locktype = VRWLOCK_WRITE;
                  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)
            io->io_new_size = new_size;

      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 > xip->i_size) {
            error = xfs_zero_eof(vp, io, 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 = -remove_suid(file->f_path.dentry);
            if (unlikely(error)) {
                  goto out_unlock_internal;
            }
      }

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

      if ((ioflags & IO_ISDIRECT)) {
            if (VN_CACHED(vp)) {
                  WARN_ON(need_i_mutex == 0);
                  xfs_inval_cached_trace(io, pos, -1,
                              ctooff(offtoct(pos)), -1);
                  error = xfs_flushinval_pages(xip,
                              ctooff(offtoct(pos)),
                              -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(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;

                  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(xip, DM_EVENT_NOSPACE) && !(ioflags & IO_INVIS)) {
            xfs_rwunlock(xip, 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 (need_i_mutex)
                  mutex_lock(&inode->i_mutex);
            xfs_rwlock(xip, locktype);
            if (error)
                  goto out_unlock_internal;
            pos = xip->i_size;
            ret = 0;
            goto retry;
      }

      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);
      }

      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_rwunlock(xip, locktype);
            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_rwlock(xip, locktype);
            error2 = xfs_write_sync_logforce(mp, xip);
            if (!error)
                  error = error2;
      }

 out_unlock_internal:
      if (io->io_new_size) {
            xfs_ilock(xip, XFS_ILOCK_EXCL);
            io->io_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_rwunlock(xip, locktype);
 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)
{
      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(
      xfs_inode_t *ip,
      xfs_off_t   offset,
      ssize_t           count,
      int         flags,
      xfs_iomap_t *iomapp,
      int         *niomaps)
{
      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;
}

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