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xfs: introduce xfs_rw_lock() helpers for locking the inode
We need to obtain the i_mutex, i_iolock and i_ilock during the read and write paths. Add a set of wrapper functions to neatly encapsulate the lock ordering and shared/exclusive semantics to make the locking easier to follow and get right. Note that this changes some of the exclusive locking serialisation in that serialisation will occur against the i_mutex instead of the XFS_IOLOCK_EXCL. This does not change any behaviour, and it is arguably more efficient to use the mutex for such serialisation than the rw_sem. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Dave Chinner
Dave Chinner
parent
4c5cfd1b41
commit
487f84f3f8
@ -40,6 +40,40 @@
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static const struct vm_operations_struct xfs_file_vm_ops;
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/*
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* Locking primitives for read and write IO paths to ensure we consistently use
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* and order the inode->i_mutex, ip->i_lock and ip->i_iolock.
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*/
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static inline void
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xfs_rw_ilock(
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struct xfs_inode *ip,
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int type)
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{
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if (type & XFS_IOLOCK_EXCL)
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mutex_lock(&VFS_I(ip)->i_mutex);
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xfs_ilock(ip, type);
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}
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static inline void
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xfs_rw_iunlock(
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struct xfs_inode *ip,
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int type)
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{
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xfs_iunlock(ip, type);
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if (type & XFS_IOLOCK_EXCL)
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mutex_unlock(&VFS_I(ip)->i_mutex);
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}
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static inline void
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xfs_rw_ilock_demote(
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struct xfs_inode *ip,
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int type)
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{
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xfs_ilock_demote(ip, type);
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if (type & XFS_IOLOCK_EXCL)
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mutex_unlock(&VFS_I(ip)->i_mutex);
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}
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/*
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* xfs_iozero
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*
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@ -262,22 +296,21 @@ xfs_file_aio_read(
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if (XFS_FORCED_SHUTDOWN(mp))
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return -EIO;
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if (unlikely(ioflags & IO_ISDIRECT))
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mutex_lock(&inode->i_mutex);
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xfs_ilock(ip, XFS_IOLOCK_SHARED);
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if (unlikely(ioflags & IO_ISDIRECT)) {
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xfs_rw_ilock(ip, XFS_IOLOCK_EXCL);
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if (inode->i_mapping->nrpages) {
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ret = -xfs_flushinval_pages(ip,
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(iocb->ki_pos & PAGE_CACHE_MASK),
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-1, FI_REMAPF_LOCKED);
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if (ret) {
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xfs_rw_iunlock(ip, XFS_IOLOCK_EXCL);
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return ret;
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}
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}
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mutex_unlock(&inode->i_mutex);
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if (ret) {
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xfs_iunlock(ip, XFS_IOLOCK_SHARED);
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return ret;
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}
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}
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xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
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} else
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xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
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trace_xfs_file_read(ip, size, iocb->ki_pos, ioflags);
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@ -285,7 +318,7 @@ xfs_file_aio_read(
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if (ret > 0)
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XFS_STATS_ADD(xs_read_bytes, ret);
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xfs_iunlock(ip, XFS_IOLOCK_SHARED);
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xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
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return ret;
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}
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@ -309,7 +342,7 @@ xfs_file_splice_read(
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if (XFS_FORCED_SHUTDOWN(ip->i_mount))
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return -EIO;
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xfs_ilock(ip, XFS_IOLOCK_SHARED);
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xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
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trace_xfs_file_splice_read(ip, count, *ppos, ioflags);
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@ -317,7 +350,7 @@ xfs_file_splice_read(
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if (ret > 0)
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XFS_STATS_ADD(xs_read_bytes, ret);
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xfs_iunlock(ip, XFS_IOLOCK_SHARED);
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xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
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return ret;
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}
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@ -338,10 +371,10 @@ xfs_aio_write_isize_update(
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*ppos = isize;
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if (*ppos > ip->i_size) {
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xfs_ilock(ip, XFS_ILOCK_EXCL);
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xfs_rw_ilock(ip, XFS_ILOCK_EXCL);
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if (*ppos > ip->i_size)
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ip->i_size = *ppos;
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xfs_iunlock(ip, XFS_ILOCK_EXCL);
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xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
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}
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}
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@ -356,14 +389,22 @@ xfs_aio_write_newsize_update(
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struct xfs_inode *ip)
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{
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if (ip->i_new_size) {
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xfs_ilock(ip, XFS_ILOCK_EXCL);
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xfs_rw_ilock(ip, XFS_ILOCK_EXCL);
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ip->i_new_size = 0;
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if (ip->i_d.di_size > ip->i_size)
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ip->i_d.di_size = ip->i_size;
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xfs_iunlock(ip, XFS_ILOCK_EXCL);
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xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
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}
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}
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/*
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* xfs_file_splice_write() does not use xfs_rw_ilock() because
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* generic_file_splice_write() takes the i_mutex itself. This, in theory,
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* couuld cause lock inversions between the aio_write path and the splice path
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* if someone is doing concurrent splice(2) based writes and write(2) based
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* writes to the same inode. The only real way to fix this is to re-implement
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* the generic code here with correct locking orders.
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*/
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STATIC ssize_t
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xfs_file_splice_write(
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struct pipe_inode_info *pipe,
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@ -604,7 +645,6 @@ xfs_file_aio_write(
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xfs_fsize_t new_size;
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int iolock;
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size_t ocount = 0, count;
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int need_i_mutex;
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XFS_STATS_INC(xs_write_calls);
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@ -631,21 +671,17 @@ xfs_file_aio_write(
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relock:
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if (ioflags & IO_ISDIRECT) {
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iolock = XFS_IOLOCK_SHARED;
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need_i_mutex = 0;
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} else {
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iolock = XFS_IOLOCK_EXCL;
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need_i_mutex = 1;
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mutex_lock(&inode->i_mutex);
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}
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xfs_ilock(ip, XFS_ILOCK_EXCL|iolock);
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start:
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xfs_rw_ilock(ip, XFS_ILOCK_EXCL|iolock);
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ret = generic_write_checks(file, &pos, &count,
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S_ISBLK(inode->i_mode));
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if (ret) {
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xfs_iunlock(ip, XFS_ILOCK_EXCL|iolock);
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goto out_unlock_mutex;
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xfs_rw_iunlock(ip, XFS_ILOCK_EXCL|iolock);
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return ret;
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}
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if (ioflags & IO_ISDIRECT) {
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@ -654,16 +690,20 @@ start:
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mp->m_rtdev_targp : mp->m_ddev_targp;
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if ((pos & target->bt_smask) || (count & target->bt_smask)) {
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xfs_iunlock(ip, XFS_ILOCK_EXCL|iolock);
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xfs_rw_iunlock(ip, XFS_ILOCK_EXCL|iolock);
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return XFS_ERROR(-EINVAL);
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}
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if (!need_i_mutex && (mapping->nrpages || pos > ip->i_size)) {
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xfs_iunlock(ip, XFS_ILOCK_EXCL|iolock);
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/*
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* For direct I/O, if there are cached pages or we're extending
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* the file, we need IOLOCK_EXCL until we're sure the bytes at
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* the new EOF have been zeroed and/or the cached pages are
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* flushed out. Upgrade the I/O lock and start again.
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*/
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if (iolock != XFS_IOLOCK_EXCL &&
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(mapping->nrpages || pos > ip->i_size)) {
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xfs_rw_iunlock(ip, XFS_ILOCK_EXCL|iolock);
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iolock = XFS_IOLOCK_EXCL;
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need_i_mutex = 1;
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mutex_lock(&inode->i_mutex);
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xfs_ilock(ip, XFS_ILOCK_EXCL|iolock);
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goto start;
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}
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}
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@ -687,11 +727,11 @@ start:
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if (pos > ip->i_size) {
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ret = -xfs_zero_eof(ip, pos, ip->i_size);
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if (ret) {
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xfs_iunlock(ip, XFS_ILOCK_EXCL);
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xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
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goto out_unlock_internal;
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}
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}
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xfs_iunlock(ip, XFS_ILOCK_EXCL);
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xfs_rw_iunlock(ip, XFS_ILOCK_EXCL);
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/*
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* If we're writing the file then make sure to clear the
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@ -708,7 +748,7 @@ start:
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if ((ioflags & IO_ISDIRECT)) {
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if (mapping->nrpages) {
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WARN_ON(need_i_mutex == 0);
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WARN_ON(iolock != XFS_IOLOCK_EXCL);
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ret = -xfs_flushinval_pages(ip,
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(pos & PAGE_CACHE_MASK),
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-1, FI_REMAPF_LOCKED);
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@ -716,13 +756,10 @@ start:
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goto out_unlock_internal;
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}
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if (need_i_mutex) {
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if (iolock == XFS_IOLOCK_EXCL) {
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/* demote the lock now the cached pages are gone */
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xfs_ilock_demote(ip, XFS_IOLOCK_EXCL);
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mutex_unlock(&inode->i_mutex);
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xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
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iolock = XFS_IOLOCK_SHARED;
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need_i_mutex = 0;
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}
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trace_xfs_file_direct_write(ip, count, iocb->ki_pos, ioflags);
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@ -740,7 +777,7 @@ start:
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count -= ret;
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ioflags &= ~IO_ISDIRECT;
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xfs_iunlock(ip, iolock);
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xfs_rw_iunlock(ip, iolock);
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goto relock;
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}
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} else {
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@ -775,14 +812,9 @@ write_retry:
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loff_t end = pos + ret - 1;
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int error, error2;
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xfs_iunlock(ip, iolock);
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if (need_i_mutex)
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mutex_unlock(&inode->i_mutex);
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xfs_rw_iunlock(ip, iolock);
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error = filemap_write_and_wait_range(mapping, pos, end);
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if (need_i_mutex)
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mutex_lock(&inode->i_mutex);
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xfs_ilock(ip, iolock);
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xfs_rw_ilock(ip, iolock);
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error2 = -xfs_file_fsync(file,
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(file->f_flags & __O_SYNC) ? 0 : 1);
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@ -794,10 +826,7 @@ write_retry:
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out_unlock_internal:
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xfs_aio_write_newsize_update(ip);
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xfs_iunlock(ip, iolock);
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out_unlock_mutex:
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if (need_i_mutex)
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mutex_unlock(&inode->i_mutex);
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xfs_rw_iunlock(ip, iolock);
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return ret;
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}
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