diff options
| -rw-r--r-- | fs/xfs/linux-2.6/xfs_file.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/fs/xfs/linux-2.6/xfs_file.c b/fs/xfs/linux-2.6/xfs_file.c index 7f782af286bf..93cc02d70c62 100644 --- a/fs/xfs/linux-2.6/xfs_file.c +++ b/fs/xfs/linux-2.6/xfs_file.c @@ -309,7 +309,19 @@ xfs_file_aio_read( if (XFS_FORCED_SHUTDOWN(mp)) return -EIO; - if (unlikely(ioflags & IO_ISDIRECT)) { + /* + * Locking is a bit tricky here. If we take an exclusive lock + * for direct IO, we effectively serialise all new concurrent + * read IO to this file and block it behind IO that is currently in + * progress because IO in progress holds the IO lock shared. We only + * need to hold the lock exclusive to blow away the page cache, so + * only take lock exclusively if the page cache needs invalidation. + * This allows the normal direct IO case of no page cache pages to + * proceeed concurrently without serialisation. + */ + xfs_rw_ilock(ip, XFS_IOLOCK_SHARED); + if ((ioflags & IO_ISDIRECT) && inode->i_mapping->nrpages) { + xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED); xfs_rw_ilock(ip, XFS_IOLOCK_EXCL); if (inode->i_mapping->nrpages) { @@ -322,8 +334,7 @@ xfs_file_aio_read( } } xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL); - } else - xfs_rw_ilock(ip, XFS_IOLOCK_SHARED); + } trace_xfs_file_read(ip, size, iocb->ki_pos, ioflags); |