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authorDave Chinner <dchinner@redhat.com>2018-05-02 12:54:54 -0700
committerDarrick J. Wong <darrick.wong@oracle.com>2018-05-09 10:04:01 -0700
commitdfa03a5f8076c6bf79a9f68ef8f559fb8999cec1 (patch)
treeb0880e4291183eb569e9a7fcc145e108173f6f70 /fs/xfs/xfs_iomap.c
parentd0641780940a9842cbf62114bc8422012c7d88c4 (diff)
downloadlinux-dfa03a5f8076c6bf79a9f68ef8f559fb8999cec1.tar.bz2
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>
Diffstat (limited to 'fs/xfs/xfs_iomap.c')
-rw-r--r--fs/xfs/xfs_iomap.c98
1 files changed, 61 insertions, 37 deletions
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);