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authorChristoph Hellwig <hch@infradead.org>2011-11-19 13:13:41 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2011-11-26 09:10:05 -0800
commit3da97f9710ca1df6cebe2558896dae3ed62337be (patch)
tree84f34c67c903c1dcbbb2fec9277835d957387f2e
parent16ba92e591d31d3213956e581867f46892648038 (diff)
downloadlinux-linaro-stable-3da97f9710ca1df6cebe2558896dae3ed62337be.tar.gz
xfs: avoid direct I/O write vs buffered I/O race
commit c58cb165bd44de8aaee9755a144136ae743be116 upstream. 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@lst.de> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Alex Elder <aelder@sgi.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--fs/xfs/linux-2.6/xfs_file.c17
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 93cc02d70c62..b679198dcc01 100644
--- a/fs/xfs/linux-2.6/xfs_file.c
+++ b/fs/xfs/linux-2.6/xfs_file.c
@@ -669,6 +669,7 @@ xfs_file_aio_write_checks(
xfs_fsize_t new_size;
int error = 0;
+ xfs_rw_ilock(ip, XFS_ILOCK_EXCL);
error = generic_write_checks(file, pos, count, S_ISBLK(inode->i_mode));
if (error) {
xfs_rw_iunlock(ip, XFS_ILOCK_EXCL | *iolock);
@@ -760,14 +761,24 @@ 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);
ret = xfs_file_aio_write_checks(file, &pos, &count, iolock);
if (ret)
return ret;
+ /*
+ * 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);
+ }
+
if (mapping->nrpages) {
- WARN_ON(*iolock != XFS_IOLOCK_EXCL);
ret = -xfs_flushinval_pages(ip, (pos & PAGE_CACHE_MASK), -1,
FI_REMAPF_LOCKED);
if (ret)
@@ -812,7 +823,7 @@ 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, iolock);
if (ret)