Currently a buffered reader or writer can add pages to the pagecache
while we are waiting for the iolock in xfs_file_dio_aio_write. Prevent
this by re-checking mapping->nrpages after we got the iolock, and if
nessecary upgrade the lock to exclusive mode. To simplify this a bit
only take the ilock inside of xfs_file_aio_write_checks.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Index: xfs/fs/xfs/xfs_file.c
===================================================================
--- xfs.orig/fs/xfs/xfs_file.c 2011-08-27 08:22:18.537779834 +0200
+++ xfs/fs/xfs/xfs_file.c 2011-08-27 08:31:43.296278506 +0200
@@ -680,6 +680,7 @@ xfs_file_aio_write_checks(
xfs_fsize_t new_size;
int error = 0;
+ xfs_rw_ilock(ip, XFS_ILOCK_EXCL);
*new_sizep = 0;
restart:
error = generic_write_checks(file, pos, count, S_ISBLK(inode->i_mode));
@@ -802,14 +803,24 @@ xfs_file_dio_aio_write(
*iolock = XFS_IOLOCK_EXCL;
else
*iolock = XFS_IOLOCK_SHARED;
- xfs_rw_ilock(ip, XFS_ILOCK_EXCL | *iolock);
+ xfs_rw_ilock(ip, *iolock);
+
+ /*
+ * Recheck if there are cached pages that need invalidate after we got
+ * the iolock to protect against other threads adding new pages while
+ * we were waiting for the iolock.
+ */
+ if (mapping->nrpages && *iolock == XFS_IOLOCK_SHARED) {
+ xfs_rw_iunlock(ip, *iolock);
+ *iolock = XFS_IOLOCK_EXCL;
+ xfs_rw_ilock(ip, *iolock);
+ }
ret = xfs_file_aio_write_checks(file, &pos, &count, new_size, iolock);
if (ret)
return ret;
if (mapping->nrpages) {
- WARN_ON(*iolock != XFS_IOLOCK_EXCL);
ret = -xfs_flushinval_pages(ip, (pos & PAGE_CACHE_MASK), -1,
FI_REMAPF_LOCKED);
if (ret)
@@ -855,7 +866,7 @@ xfs_file_buffered_aio_write(
size_t count = ocount;
*iolock = XFS_IOLOCK_EXCL;
- xfs_rw_ilock(ip, XFS_ILOCK_EXCL | *iolock);
+ xfs_rw_ilock(ip, *iolock);
ret = xfs_file_aio_write_checks(file, &pos, &count, new_size, iolock);
if (ret)
_______________________________________________
xfs mailing list
xfs@xxxxxxxxxxx
http://oss.sgi.com/mailman/listinfo/xfs
