[PATCH 4.9 05/72] xfs: pull up iolock from xfs_free_eofblocks()

Greg Kroah-Hartman
2017-04-06T09:30:06Z

From: Brian Foster <bfoster@redhat.com>

commit a36b926180cda375ac2ec89e1748b47137cfc51c upstream.

xfs_free_eofblocks() requires the IOLOCK_EXCL lock, but is called from
different contexts where the lock may or may not be held. The
need_iolock parameter exists for this reason, to indicate whether
xfs_free_eofblocks() must acquire the iolock itself before it can
proceed.

This is ugly and confusing. Simplify the semantics of
xfs_free_eofblocks() to require the caller to acquire the iolock
appropriately and kill the need_iolock parameter. While here, the mp
param can be removed as well as the xfs_mount is accessible from the
xfs_inode structure. This patch does not change behavior.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/xfs/xfs_bmap_util.c | 41 +++++++++++++++------------------------
fs/xfs/xfs_bmap_util.h | 3 --
fs/xfs/xfs_icache.c | 24 ++++++++++++++---------
fs/xfs/xfs_inode.c | 51 ++++++++++++++++++++++++++-----------------------
4 files changed, 60 insertions(+), 59 deletions(-)

--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -917,17 +917,18 @@ xfs_can_free_eofblocks(struct xfs_inode
*/
int
xfs_free_eofblocks(
- xfs_mount_t *mp,
- xfs_inode_t *ip,
- bool need_iolock)
+ struct xfs_inode *ip)
{
- xfs_trans_t *tp;
- int error;
- xfs_fileoff_t end_fsb;
- xfs_fileoff_t last_fsb;
- xfs_filblks_t map_len;
- int nimaps;
- xfs_bmbt_irec_t imap;
+ struct xfs_trans *tp;
+ int error;
+ xfs_fileoff_t end_fsb;
+ xfs_fileoff_t last_fsb;
+ xfs_filblks_t map_len;
+ int nimaps;
+ struct xfs_bmbt_irec imap;
+ struct xfs_mount *mp = ip->i_mount;
+
+ ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));

/*
* Figure out if there are any blocks beyond the end
@@ -944,6 +945,10 @@ xfs_free_eofblocks(
error = xfs_bmapi_read(ip, end_fsb, map_len, &imap, &nimaps, 0);
xfs_iunlock(ip, XFS_ILOCK_SHARED);

+ /*
+ * If there are blocks after the end of file, truncate the file to its
+ * current size to free them up.
+ */
if (!error && (nimaps != 0) &&
(imap.br_startblock != HOLESTARTBLOCK ||
ip->i_delayed_blks)) {
@@ -954,22 +959,10 @@ xfs_free_eofblocks(
if (error)
return error;

- /*
- * There are blocks after the end of file.
- * Free them up now by truncating the file to
- * its current size.
- */
- if (need_iolock) {
- if (!xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL))
- return -EAGAIN;
- }
-
error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0,
&tp);
if (error) {
ASSERT(XFS_FORCED_SHUTDOWN(mp));
- if (need_iolock)
- xfs_iunlock(ip, XFS_IOLOCK_EXCL);
return error;
}

@@ -997,8 +990,6 @@ xfs_free_eofblocks(
}

xfs_iunlock(ip, XFS_ILOCK_EXCL);
- if (need_iolock)
- xfs_iunlock(ip, XFS_IOLOCK_EXCL);
}
return error;
}
@@ -1415,7 +1406,7 @@ xfs_shift_file_space(
* into the accessible region of the file.
*/
if (xfs_can_free_eofblocks(ip, true)) {
- error = xfs_free_eofblocks(mp, ip, false);
+ error = xfs_free_eofblocks(ip);
if (error)
return error;
}
--- a/fs/xfs/xfs_bmap_util.h
+++ b/fs/xfs/xfs_bmap_util.h
@@ -63,8 +63,7 @@ int xfs_insert_file_space(struct xfs_ino

/* EOF block manipulation functions */
bool xfs_can_free_eofblocks(struct xfs_inode *ip, bool force);
-int xfs_free_eofblocks(struct xfs_mount *mp, struct xfs_inode *ip,
- bool need_iolock);
+int xfs_free_eofblocks(struct xfs_inode *ip);

int xfs_swap_extents(struct xfs_inode *ip, struct xfs_inode *tip,
struct xfs_swapext *sx);
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -1324,7 +1324,7 @@ xfs_inode_free_eofblocks(
int flags,
void *args)
{
- int ret;
+ int ret = 0;
struct xfs_eofblocks *eofb = args;
bool need_iolock = true;
int match;
@@ -1360,19 +1360,25 @@ xfs_inode_free_eofblocks(
return 0;

/*
- * A scan owner implies we already hold the iolock. Skip it in
- * xfs_free_eofblocks() to avoid deadlock. This also eliminates
- * the possibility of EAGAIN being returned.
+ * A scan owner implies we already hold the iolock. Skip it here
+ * to avoid deadlock.
*/
if (eofb->eof_scan_owner == ip->i_ino)
need_iolock = false;
}

- ret = xfs_free_eofblocks(ip->i_mount, ip, need_iolock);
-
- /* don't revisit the inode if we're not waiting */
- if (ret == -EAGAIN && !(flags & SYNC_WAIT))
- ret = 0;
+ /*
+ * If the caller is waiting, return -EAGAIN to keep the background
+ * scanner moving and revisit the inode in a subsequent pass.
+ */
+ if (need_iolock && !xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL)) {
+ if (flags & SYNC_WAIT)
+ ret = -EAGAIN;
+ return ret;
+ }
+ ret = xfs_free_eofblocks(ip);
+ if (need_iolock)
+ xfs_iunlock(ip, XFS_IOLOCK_EXCL);

return ret;
}
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1701,32 +1701,34 @@ xfs_release(
if (xfs_can_free_eofblocks(ip, false)) {

/*
+ * Check if the inode is being opened, written and closed
+ * frequently and we have delayed allocation blocks outstanding
+ * (e.g. streaming writes from the NFS server), truncating the
+ * blocks past EOF will cause fragmentation to occur.
+ *
+ * In this case don't do the truncation, but we have to be
+ * careful how we detect this case. Blocks beyond EOF show up as
+ * i_delayed_blks even when the inode is clean, so we need to
+ * truncate them away first before checking for a dirty release.
+ * Hence on the first dirty close we will still remove the
+ * speculative allocation, but after that we will leave it in
+ * place.
+ */
+ if (xfs_iflags_test(ip, XFS_IDIRTY_RELEASE))
+ return 0;
+ /*
* If we can't get the iolock just skip truncating the blocks
* past EOF because we could deadlock with the mmap_sem
- * otherwise. We'll get another chance to drop them once the
+ * otherwise. We'll get another chance to drop them once the
* last reference to the inode is dropped, so we'll never leak
* blocks permanently.
- *
- * Further, check if the inode is being opened, written and
- * closed frequently and we have delayed allocation blocks
- * outstanding (e.g. streaming writes from the NFS server),
- * truncating the blocks past EOF will cause fragmentation to
- * occur.
- *
- * In this case don't do the truncation, either, but we have to
- * be careful how we detect this case. Blocks beyond EOF show
- * up as i_delayed_blks even when the inode is clean, so we
- * need to truncate them away first before checking for a dirty
- * release. Hence on the first dirty close we will still remove
- * the speculative allocation, but after that we will leave it
- * in place.
*/
- if (xfs_iflags_test(ip, XFS_IDIRTY_RELEASE))
- return 0;
-
- error = xfs_free_eofblocks(mp, ip, true);
- if (error && error != -EAGAIN)
- return error;
+ if (xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL)) {
+ error = xfs_free_eofblocks(ip);
+ xfs_iunlock(ip, XFS_IOLOCK_EXCL);
+ if (error)
+ return error;
+ }

/* delalloc blocks after truncation means it really is dirty */
if (ip->i_delayed_blks)
@@ -1913,8 +1915,11 @@ xfs_inactive(
* cache. Post-eof blocks must be freed, lest we end up with
* broken free space accounting.
*/
- if (xfs_can_free_eofblocks(ip, true))
- xfs_free_eofblocks(mp, ip, false);
+ if (xfs_can_free_eofblocks(ip, true)) {
+ xfs_ilock(ip, XFS_IOLOCK_EXCL);
+ xfs_free_eofblocks(ip);
+ xfs_iunlock(ip, XFS_IOLOCK_EXCL);
+ }

return;
}