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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 <dchinner@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Dave Chinner 2018-05-02 12:54:54 -07:00 committed by Darrick J. Wong
parent d064178094
commit dfa03a5f80
1 changed files with 61 additions and 37 deletions
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98
fs/xfs/xfs_iomap.c
View File

@ -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);