| Message ID | 20170921155246.4352-1-eguan@redhat.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
On Thu, Sep 21, 2017 at 11:52:46PM +0800, Eryu Guan wrote: > Since commit d531d91d6990 ("xfs: always use unwritten extents for > direct I/O writes"), we start allocating unwritten extents for all > direct writes to allow appending aio in XFS. > > But for dio writes that could extend file size we update the in-core > inode size first, then convert the unwritten extents to real > allocations at dio completion time in xfs_dio_write_end_io(). Thus a > racing direct read could see the new i_size and find the unwritten > extents first and read zeros instead of actual data, if the direct > writer also takes a shared iolock. > > Fix it by updating the in-core inode size after the unwritten extent > conversion. To do this, introduce a new boolean argument to > xfs_iomap_write_unwritten() to tell if we want to update in-core > i_size or not. > > Suggested-by: Brian Foster <bfoster@redhat.com> > Reviewed-by: Brian Foster <bfoster@redhat.com> > Signed-off-by: Eryu Guan <eguan@redhat.com> > --- > v2: > - fix comments by copying Brian's words :) > - fix code style, remove unnecessary blank lines and braces > > v1: https://marc.info/?l=linux-xfs&m=150599032124565&w=2 > > fs/xfs/xfs_aops.c | 3 ++- > fs/xfs/xfs_file.c | 33 +++++++++++++++++++-------------- > fs/xfs/xfs_iomap.c | 7 +++++-- > fs/xfs/xfs_iomap.h | 2 +- > fs/xfs/xfs_pnfs.c | 2 +- > 5 files changed, 28 insertions(+), 19 deletions(-) > > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c > index 29172609f2a3..f18e5932aec4 100644 > --- a/fs/xfs/xfs_aops.c > +++ b/fs/xfs/xfs_aops.c > @@ -343,7 +343,8 @@ xfs_end_io( > error = xfs_reflink_end_cow(ip, offset, size); > break; > case XFS_IO_UNWRITTEN: > - error = xfs_iomap_write_unwritten(ip, offset, size); > + /* writeback should never update isize */ > + error = xfs_iomap_write_unwritten(ip, offset, size, false); Can we expand this to /* writeback should never update the in-core inode size */ > @@ -459,20 +473,11 @@ xfs_dio_write_end_io( > spin_lock(&ip->i_flags_lock); > if (offset + size > i_size_read(inode)) { > i_size_write(inode, offset + size); > + spin_unlock(&ip->i_flags_lock); > error = xfs_setfilesize(ip, offset, size); > + } else { > + spin_unlock(&ip->i_flags_lock); > + } I find the old update_isize scheme a little easier to read, but it shouldn't matter in the end: spin_lock(&ip->i_flags_lock); if (offset + size > i_size_read(inode)) { i_size_write(inode, offset + size); update_isize = true; } spin_unlock(&ip->i_flags_lock); if (!update_isize) return 0; return xfs_setfilesize(ip, offset, size); > xfs_bmbt_irec_t imap; > struct xfs_defer_ops dfops; > + struct inode *inode = VFS_I(ip); > xfs_fsize_t i_size; > uint resblks; > int error; > @@ -899,7 +901,8 @@ xfs_iomap_write_unwritten( > i_size = XFS_FSB_TO_B(mp, offset_fsb + count_fsb); > if (i_size > offset + count) > i_size = offset + count; > - > + if (update_isize && i_size > i_size_read(inode)) > + i_size_write(inode, i_size); > i_size = xfs_new_eof(ip, i_size); > if (i_size) { > ip->i_d.di_size = i_size; I wonder if this might be cleaner if we expand xfs_new_eof for the update_isize case. Something like the untested helper below: static bool xfs_alloc_update_isize( struct xfs_inode *ip, xfs_fileoff_t offset_fsb, xfs_filblks_t count_fsb, bool update_incore_isize) { xfs_fsize_t i_size; i_size = XFS_FSB_TO_B(ip->i_mount, offset_fsb + count_fsb); if (i_size > offset + count) i_size = offset + count; if (update_isize) { if (i_size <= i_size_read(inode)) return; i_size_write(inode, i_size); } else { i_size = xfs_new_eof(ip, i_size); if (!i_size) return; } ip->i_d.di_size = i_size; xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE); } -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c index 29172609f2a3..f18e5932aec4 100644 --- a/fs/xfs/xfs_aops.c +++ b/fs/xfs/xfs_aops.c @@ -343,7 +343,8 @@ xfs_end_io( error = xfs_reflink_end_cow(ip, offset, size); break; case XFS_IO_UNWRITTEN: - error = xfs_iomap_write_unwritten(ip, offset, size); + /* writeback should never update isize */ + error = xfs_iomap_write_unwritten(ip, offset, size, false); break; default: ASSERT(!xfs_ioend_is_append(ioend) || ioend->io_append_trans); diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index 350b6d43ba23..309e26c9dddb 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -434,7 +434,6 @@ xfs_dio_write_end_io( struct inode *inode = file_inode(iocb->ki_filp); struct xfs_inode *ip = XFS_I(inode); loff_t offset = iocb->ki_pos; - bool update_size = false; int error = 0; trace_xfs_end_io_direct_write(ip, offset, size); @@ -445,6 +444,21 @@ xfs_dio_write_end_io( if (size <= 0) return size; + if (flags & IOMAP_DIO_COW) { + error = xfs_reflink_end_cow(ip, offset, size); + if (error) + return error; + } + + /* + * Unwritten conversion updates the in-core isize after extent + * conversion but before updating the on-disk size. Updating isize any + * earlier allows a racing dio read to find unwritten extents before + * they are converted. + */ + if (flags & IOMAP_DIO_UNWRITTEN) + return xfs_iomap_write_unwritten(ip, offset, size, true); + /* * We need to update the in-core inode size here so that we don't end up * with the on-disk inode size being outside the in-core inode size. We @@ -459,20 +473,11 @@ xfs_dio_write_end_io( spin_lock(&ip->i_flags_lock); if (offset + size > i_size_read(inode)) { i_size_write(inode, offset + size); - update_size = true; - } - spin_unlock(&ip->i_flags_lock); - - if (flags & IOMAP_DIO_COW) { - error = xfs_reflink_end_cow(ip, offset, size); - if (error) - return error; - } - - if (flags & IOMAP_DIO_UNWRITTEN) - error = xfs_iomap_write_unwritten(ip, offset, size); - else if (update_size) + spin_unlock(&ip->i_flags_lock); error = xfs_setfilesize(ip, offset, size); + } else { + spin_unlock(&ip->i_flags_lock); + } return error; } diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index a1909bc064e9..f179bdf1644d 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -829,7 +829,8 @@ int xfs_iomap_write_unwritten( xfs_inode_t *ip, xfs_off_t offset, - xfs_off_t count) + xfs_off_t count, + bool update_isize) { xfs_mount_t *mp = ip->i_mount; xfs_fileoff_t offset_fsb; @@ -840,6 +841,7 @@ xfs_iomap_write_unwritten( xfs_trans_t *tp; xfs_bmbt_irec_t imap; struct xfs_defer_ops dfops; + struct inode *inode = VFS_I(ip); xfs_fsize_t i_size; uint resblks; int error; @@ -899,7 +901,8 @@ xfs_iomap_write_unwritten( i_size = XFS_FSB_TO_B(mp, offset_fsb + count_fsb); if (i_size > offset + count) i_size = offset + count; - + if (update_isize && i_size > i_size_read(inode)) + i_size_write(inode, i_size); i_size = xfs_new_eof(ip, i_size); if (i_size) { ip->i_d.di_size = i_size; diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h index 00db3ecea084..ee535065c5d0 100644 --- a/fs/xfs/xfs_iomap.h +++ b/fs/xfs/xfs_iomap.h @@ -27,7 +27,7 @@ int xfs_iomap_write_direct(struct xfs_inode *, xfs_off_t, size_t, struct xfs_bmbt_irec *, int); int xfs_iomap_write_allocate(struct xfs_inode *, int, xfs_off_t, struct xfs_bmbt_irec *); -int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t); +int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t, bool); void xfs_bmbt_to_iomap(struct xfs_inode *, struct iomap *, struct xfs_bmbt_irec *); diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c index 2f2dc3c09ad0..4246876df7b7 100644 --- a/fs/xfs/xfs_pnfs.c +++ b/fs/xfs/xfs_pnfs.c @@ -274,7 +274,7 @@ xfs_fs_commit_blocks( (end - 1) >> PAGE_SHIFT); WARN_ON_ONCE(error); - error = xfs_iomap_write_unwritten(ip, start, length); + error = xfs_iomap_write_unwritten(ip, start, length, false); if (error) goto out_drop_iolock; }
Since commit d531d91d6990 ("xfs: always use unwritten extents for direct I/O writes"), we start allocating unwritten extents for all direct writes to allow appending aio in XFS. But for dio writes that could extend file size we update the in-core inode size first, then convert the unwritten extents to real allocations at dio completion time in xfs_dio_write_end_io(). Thus a racing direct read could see the new i_size and find the unwritten extents first and read zeros instead of actual data, if the direct writer also takes a shared iolock. Fix it by updating the in-core inode size after the unwritten extent conversion. To do this, introduce a new boolean argument to xfs_iomap_write_unwritten() to tell if we want to update in-core i_size or not. Suggested-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Eryu Guan <eguan@redhat.com> --- v2: - fix comments by copying Brian's words :) - fix code style, remove unnecessary blank lines and braces v1: https://marc.info/?l=linux-xfs&m=150599032124565&w=2 fs/xfs/xfs_aops.c | 3 ++- fs/xfs/xfs_file.c | 33 +++++++++++++++++++-------------- fs/xfs/xfs_iomap.c | 7 +++++-- fs/xfs/xfs_iomap.h | 2 +- fs/xfs/xfs_pnfs.c | 2 +- 5 files changed, 28 insertions(+), 19 deletions(-)