From dfa03a5f8076c6bf79a9f68ef8f559fb8999cec1 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Wed, 2 May 2018 12:54:54 -0700 Subject: xfs: clean up locking in xfs_file_iomap_begin Rather than checking what kind of locking is needed in a helper function and then jumping through hoops to do the locking in line, move the locking to the helper function that does all the checks and rename it to xfs_ilock_for_iomap(). This also allows us to hoist all the nonblocking checks up into the locking helper, further simplifier the code flow in xfs_file_iomap_begin() and making it easier to understand. Signed-Off-By: Dave Chinner Reviewed-by: Carlos Maiolino Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/xfs/xfs_iomap.c | 98 +++++++++++++++++++++++++++++++++--------------------- 1 file changed, 61 insertions(+), 37 deletions(-) (limited to 'fs/xfs/xfs_iomap.c') diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index 16565da67bb6..d03e65f01c89 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -946,8 +946,11 @@ error_on_bmapi_transaction: return error; } -static inline bool imap_needs_alloc(struct inode *inode, - struct xfs_bmbt_irec *imap, int nimaps) +static inline bool +imap_needs_alloc( + struct inode *inode, + struct xfs_bmbt_irec *imap, + int nimaps) { return !nimaps || imap->br_startblock == HOLESTARTBLOCK || @@ -955,31 +958,58 @@ static inline bool imap_needs_alloc(struct inode *inode, (IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN); } -static inline bool needs_cow_for_zeroing(struct xfs_bmbt_irec *imap, int nimaps) +static inline bool +needs_cow_for_zeroing( + struct xfs_bmbt_irec *imap, + int nimaps) { return nimaps && imap->br_startblock != HOLESTARTBLOCK && imap->br_state != XFS_EXT_UNWRITTEN; } -static inline bool need_excl_ilock(struct xfs_inode *ip, unsigned flags) +static int +xfs_ilock_for_iomap( + struct xfs_inode *ip, + unsigned flags, + unsigned *lockmode) { + unsigned mode = XFS_ILOCK_SHARED; + /* * COW writes may allocate delalloc space or convert unwritten COW * extents, so we need to make sure to take the lock exclusively here. */ - if (xfs_is_reflink_inode(ip) && (flags & (IOMAP_WRITE | IOMAP_ZERO))) - return true; + if (xfs_is_reflink_inode(ip) && (flags & (IOMAP_WRITE | IOMAP_ZERO))) { + /* + * FIXME: It could still overwrite on unshared extents and not + * need allocation. + */ + if (flags & IOMAP_NOWAIT) + return -EAGAIN; + mode = XFS_ILOCK_EXCL; + } /* - * Extents not yet cached requires exclusive access, don't block. - * This is an opencoded xfs_ilock_data_map_shared() to cater for the + * Extents not yet cached requires exclusive access, don't block. This + * is an opencoded xfs_ilock_data_map_shared() call but with * non-blocking behaviour. */ - if (ip->i_d.di_format == XFS_DINODE_FMT_BTREE && - !(ip->i_df.if_flags & XFS_IFEXTENTS)) - return true; - return false; + if (!(ip->i_df.if_flags & XFS_IFEXTENTS)) { + if (flags & IOMAP_NOWAIT) + return -EAGAIN; + mode = XFS_ILOCK_EXCL; + } + + if (flags & IOMAP_NOWAIT) { + if (!xfs_ilock_nowait(ip, mode)) + return -EAGAIN; + } else { + xfs_ilock(ip, mode); + } + + *lockmode = mode; + return 0; } static int @@ -1007,19 +1037,15 @@ xfs_file_iomap_begin( return xfs_file_iomap_begin_delay(inode, offset, length, iomap); } - if (need_excl_ilock(ip, flags)) - lockmode = XFS_ILOCK_EXCL; - else - lockmode = XFS_ILOCK_SHARED; - - if (flags & IOMAP_NOWAIT) { - if (!(ip->i_df.if_flags & XFS_IFEXTENTS)) - return -EAGAIN; - if (!xfs_ilock_nowait(ip, lockmode)) - return -EAGAIN; - } else { - xfs_ilock(ip, lockmode); - } + /* + * Lock the inode in the manner required for the specified operation and + * check for as many conditions that would result in blocking as + * possible. This removes most of the non-blocking checks from the + * mapping code below. + */ + error = xfs_ilock_for_iomap(ip, flags, &lockmode); + if (error) + return error; ASSERT(offset <= mp->m_super->s_maxbytes); if (offset > mp->m_super->s_maxbytes - length) @@ -1044,19 +1070,17 @@ xfs_file_iomap_begin( if (!(flags & (IOMAP_WRITE | IOMAP_ZERO))) goto out_found; - if (xfs_is_reflink_inode(ip) && - ((flags & IOMAP_WRITE) || - ((flags & IOMAP_ZERO) && needs_cow_for_zeroing(&imap, nimaps)))) { + /* + * Break shared extents if necessary. Checks for non-blocking IO have + * been done up front, so we don't need to do them here. + */ + if (xfs_is_reflink_inode(ip)) { + /* if zeroing doesn't need COW allocation, then we are done. */ + if ((flags & IOMAP_ZERO) && + !needs_cow_for_zeroing(&imap, nimaps)) + goto out_found; + if (flags & IOMAP_DIRECT) { - /* - * A reflinked inode will result in CoW alloc. - * FIXME: It could still overwrite on unshared extents - * and not need allocation. - */ - if (flags & IOMAP_NOWAIT) { - error = -EAGAIN; - goto out_unlock; - } /* may drop and re-acquire the ilock */ error = xfs_reflink_allocate_cow(ip, &imap, &shared, &lockmode); -- cgit v1.2.3