xfs: remove the i_new_size field in struct xfs_inode

Now that we use the VFS i_size field throughout XFS there is no need for the
i_new_size field any more given that the VFS i_size field gets updated
in ->write_end before unlocking the page, and thus is always uptodate when
writeback could see a page.  Removing i_new_size also has the advantage that
we will never have to trim back di_size during a failed buffered write,
given that it never gets updated past i_size.

Note that currently the generic direct I/O code only updates i_size after
calling our end_io handler, which requires a small workaround to make
sure di_size actually makes it to disk.  I hope to fix this properly in
the generic code.

A downside is that we lose the support for parallel non-overlapping O_DIRECT
appending writes that recently was added.  I don't think keeping the complex
and fragile i_new_size infrastructure for this is a good tradeoff - if we
really care about parallel appending writers we should investigate turning
the iolock into a range lock, which would also allow for parallel
non-overlapping buffered writers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 10 insertions, 62 deletions

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 86d5dc260464..632313926788 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -413,27 +413,6 @@ xfs_file_splice_read(
 }
 
 /*
- * 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 occurred.  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.
- */
-STATIC void
-xfs_aio_write_newsize_update(
-        struct xfs_inode        *ip,
-        xfs_fsize_t             new_size)
-{
-        if (new_size == ip->i_new_size) {
-                xfs_rw_ilock(ip, XFS_ILOCK_EXCL);
-                if (new_size == ip->i_new_size)
-                        ip->i_new_size = 0;
-                if (ip->i_d.di_size > i_size_read(VFS_I(ip)))
-                        ip->i_d.di_size = i_size_read(VFS_I(ip));
-                xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
-        }
-}
-
-/*
  * xfs_file_splice_write() does not use xfs_rw_ilock() because
  * generic_file_splice_write() takes the i_mutex itself. This, in theory,
  * couuld cause lock inversions between the aio_write path and the splice path
@@ -451,7 +430,6 @@ xfs_file_splice_write(
 {
         struct inode            *inode = outfilp->f_mapping->host;
         struct xfs_inode        *ip = XFS_I(inode);
-        xfs_fsize_t             new_size;
         int                     ioflags = 0;
         ssize_t                 ret;
 
@@ -465,20 +443,12 @@ xfs_file_splice_write(
 
         xfs_ilock(ip, XFS_IOLOCK_EXCL);
 
-        new_size = *ppos + count;
-
-        xfs_ilock(ip, XFS_ILOCK_EXCL);
-        if (new_size > i_size_read(inode))
-                ip->i_new_size = new_size;
-        xfs_iunlock(ip, XFS_ILOCK_EXCL);
-
         trace_xfs_file_splice_write(ip, count, *ppos, ioflags);
 
         ret = generic_file_splice_write(pipe, outfilp, ppos, count, flags);
         if (ret > 0)
                 XFS_STATS_ADD(xs_write_bytes, ret);
 
-        xfs_aio_write_newsize_update(ip, new_size);
         xfs_iunlock(ip, XFS_IOLOCK_EXCL);
         return ret;
 }
@@ -673,16 +643,13 @@ xfs_file_aio_write_checks(
         struct file             *file,
         loff_t                  *pos,
         size_t                  *count,
-        xfs_fsize_t             *new_sizep,
         int                     *iolock)
 {
         struct inode            *inode = file->f_mapping->host;
         struct xfs_inode        *ip = XFS_I(inode);
-        xfs_fsize_t             new_size;
         int                     error = 0;
 
         xfs_rw_ilock(ip, XFS_ILOCK_EXCL);
-        *new_sizep = 0;
 restart:
         error = generic_write_checks(file, pos, count, S_ISBLK(inode->i_mode));
         if (error) {
@@ -697,15 +664,13 @@ restart:
         /*
          * If the offset is beyond the size of the file, we need to zero any
          * blocks that fall between the existing EOF and the start of this
-         * write. There is no need to issue zeroing if another in-flght IO ends
-         * at or before this one If zeronig is needed and we are currently
-         * holding the iolock shared, we need to update it to exclusive which
-         * involves dropping all locks and relocking to maintain correct locking
-         * order. If we do this, restart the function to ensure all checks and
-         * values are still valid.
+         * write.  If zeroing is needed and we are currently holding the
+         * iolock shared, we need to update it to exclusive which involves
+         * dropping all locks and relocking to maintain correct locking order.
+         * If we do this, restart the function to ensure all checks and values
+         * are still valid.
          */
-        if ((ip->i_new_size && *pos > ip->i_new_size) ||
-            (!ip->i_new_size && *pos > i_size_read(inode))) {
+        if (*pos > i_size_read(inode)) {
                 if (*iolock == XFS_IOLOCK_SHARED) {
                         xfs_rw_iunlock(ip, XFS_ILOCK_EXCL | *iolock);
                         *iolock = XFS_IOLOCK_EXCL;
@@ -714,19 +679,6 @@ restart:
                 }
                 error = -xfs_zero_eof(ip, *pos, i_size_read(inode));
         }
-
-        /*
-         * If this IO extends beyond EOF, we may need to update ip->i_new_size.
-         * We have already zeroed space beyond EOF (if necessary).  Only update
-         * ip->i_new_size if this IO ends beyond any other in-flight writes.
-         */
-        new_size = *pos + *count;
-        if (new_size > i_size_read(inode)) {
-                if (new_size > ip->i_new_size)
-                        ip->i_new_size = new_size;
-                *new_sizep = new_size;
-        }
-
         xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
         if (error)
                 return error;
@@ -772,7 +724,6 @@ xfs_file_dio_aio_write(
         unsigned long           nr_segs,
         loff_t                  pos,
         size_t                  ocount,
-        xfs_fsize_t             *new_size,
         int                     *iolock)
 {
         struct file             *file = iocb->ki_filp;
@@ -817,7 +768,7 @@ xfs_file_dio_aio_write(
                 xfs_rw_ilock(ip, *iolock);
         }
 
-        ret = xfs_file_aio_write_checks(file, &pos, &count, new_size, iolock);
+        ret = xfs_file_aio_write_checks(file, &pos, &count, iolock);
         if (ret)
                 return ret;
 
@@ -855,7 +806,6 @@ xfs_file_buffered_aio_write(
         unsigned long           nr_segs,
         loff_t                  pos,
         size_t                  ocount,
-        xfs_fsize_t             *new_size,
         int                     *iolock)
 {
         struct file             *file = iocb->ki_filp;
@@ -869,7 +819,7 @@ xfs_file_buffered_aio_write(
         *iolock = XFS_IOLOCK_EXCL;
         xfs_rw_ilock(ip, *iolock);
 
-        ret = xfs_file_aio_write_checks(file, &pos, &count, new_size, iolock);
+        ret = xfs_file_aio_write_checks(file, &pos, &count, iolock);
         if (ret)
                 return ret;
 
@@ -909,7 +859,6 @@ xfs_file_aio_write(
         ssize_t                 ret;
         int                     iolock;
         size_t                  ocount = 0;
-        xfs_fsize_t             new_size = 0;
 
         XFS_STATS_INC(xs_write_calls);
 
@@ -929,10 +878,10 @@ xfs_file_aio_write(
 
         if (unlikely(file->f_flags & O_DIRECT))
                 ret = xfs_file_dio_aio_write(iocb, iovp, nr_segs, pos,
-                                                ocount, &new_size, &iolock);
+                                                ocount, &iolock);
         else
                 ret = xfs_file_buffered_aio_write(iocb, iovp, nr_segs, pos,
-                                                ocount, &new_size, &iolock);
+                                                ocount, &iolock);
 
         if (ret <= 0)
                 goto out_unlock;
@@ -953,7 +902,6 @@ xfs_file_aio_write(
         }
 
 out_unlock:
-        xfs_aio_write_newsize_update(ip, new_size);
         xfs_rw_iunlock(ip, iolock);
         return ret;
 }