[PATCH 08/10] xfs: take the ilock shared if possible in xfs_file_iomap_begin
From: Christoph Hellwig <hch@lst.de>
Date: 2016-09-09 16:35:09
Also in:
linux-fsdevel, nvdimm
Subsystem:
filesystems (vfs and infrastructure), the rest, xfs filesystem · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds, Carlos Maiolino
We always just read the extent first, and will later lock exlusively after first dropping the lock in case we actually allocate blocks. Signed-off-by: Christoph Hellwig <hch@lst.de> --- fs/xfs/xfs_iomap.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 5d06a2d..c3cc175 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c@@ -955,6 +955,7 @@ xfs_file_iomap_begin( struct xfs_bmbt_irec imap; xfs_fileoff_t offset_fsb, end_fsb; int nimaps = 1, error = 0; + unsigned lockmode; if (XFS_FORCED_SHUTDOWN(mp)) return -EIO;
@@ -964,7 +965,7 @@ xfs_file_iomap_begin( iomap); } - xfs_ilock(ip, XFS_ILOCK_EXCL); + lockmode = xfs_ilock_data_map_shared(ip); ASSERT(offset <= mp->m_super->s_maxbytes); if ((xfs_fsize_t)offset + length > mp->m_super->s_maxbytes)
@@ -975,7 +976,7 @@ xfs_file_iomap_begin( error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap, &nimaps, XFS_BMAPI_ENTIRE); if (error) { - xfs_iunlock(ip, XFS_ILOCK_EXCL); + xfs_iunlock(ip, lockmode); return error; }
@@ -995,7 +996,8 @@ xfs_file_iomap_begin( * xfs_iomap_write_direct() expects the shared lock. It * is unlocked on return. */ - xfs_ilock_demote(ip, XFS_ILOCK_EXCL); + if (lockmode == XFS_ILOCK_EXCL) + xfs_ilock_demote(ip, lockmode); error = xfs_iomap_write_direct(ip, offset, length, &imap, nimaps); if (error)
@@ -1006,7 +1008,7 @@ xfs_file_iomap_begin( } else { ASSERT(nimaps); - xfs_iunlock(ip, XFS_ILOCK_EXCL); + xfs_iunlock(ip, lockmode); trace_xfs_iomap_found(ip, offset, length, 0, &imap); }
--
2.1.4