XFS deadlocks, and doesn't need the fancy locking anyway.
So provide a separate direct-IO path for XFS, which avoids all the extra
locking.
fs/direct-io.c | 30 ++++++++++++++++++------------
fs/xfs/linux/xfs_aops.c | 2 +-
include/linux/fs.h | 29 ++++++++++++++++++++++++++---
kernel/ksyms.c | 1 -
4 files changed, 45 insertions(+), 17 deletions(-)
diff -puN fs/direct-io.c~O_DIRECT-race-fixes-rework-XFS-fix fs/direct-io.c
--- 25/fs/direct-io.c~O_DIRECT-race-fixes-rework-XFS-fix 2003-10-01 20:26:22.000000000 -0700
+++ 25-akpm/fs/direct-io.c 2003-10-01 20:27:07.000000000 -0700
@@ -51,6 +51,10 @@
*
* If blkfactor is zero then the user's request was aligned to the filesystem's
* blocksize.
+ *
+ * needs_locking is set for regular files on direct-IO-naive filesystems. It
+ * determines whether we need to do the fancy locking which prevents direct-IO
+ * from being able to read uninitialised disk blocks.
*/
struct dio {
@@ -58,6 +62,7 @@ struct dio {
struct bio *bio; /* bio under assembly */
struct inode *inode;
int rw;
+ int needs_locking; /* doesn't change */
unsigned blkbits; /* doesn't change */
unsigned blkfactor; /* When we're using an alignment which
is finer than the filesystem's soft
@@ -121,11 +126,6 @@ struct dio {
int result; /* IO result */
};
-static inline int dio_is_reg(struct dio *dio)
-{
- return S_ISREG(dio->inode->i_mode);
-}
-
/*
* How many pages are in the queue?
*/
@@ -210,7 +210,7 @@ static void dio_complete(struct dio *dio
{
if (dio->end_io)
dio->end_io(dio->inode, offset, bytes, dio->map_bh.b_private);
- if (dio_is_reg(dio))
+ if (dio->needs_locking)
up_read(&dio->inode->i_alloc_sem);
}
@@ -473,7 +473,7 @@ static int get_more_blocks(struct dio *d
if (dio_count & blkmask)
fs_count++;
- if (dio_is_reg(dio)) {
+ if (dio->needs_locking) {
if (dio->block_in_file >= (i_size_read(dio->inode) >>
dio->blkbits))
beyond_eof = 1;
@@ -971,7 +971,7 @@ direct_io_worker(int rw, struct kiocb *i
* All new block allocations have been performed. We can let i_sem
* go now.
*/
- if (dio_is_reg(dio))
+ if (dio->needs_locking)
up(&dio->inode->i_sem);
/*
@@ -1016,9 +1016,10 @@ direct_io_worker(int rw, struct kiocb *i
* For writes to S_ISBLK files, i_sem is not held on entry; it is never taken.
*/
int
-blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
+__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
struct block_device *bdev, const struct iovec *iov, loff_t offset,
- unsigned long nr_segs, get_blocks_t get_blocks, dio_iodone_t end_io)
+ unsigned long nr_segs, get_blocks_t get_blocks, dio_iodone_t end_io,
+ int needs_special_locking)
{
int seg;
size_t size;
@@ -1028,6 +1029,7 @@ blockdev_direct_IO(int rw, struct kiocb
unsigned blocksize_mask = (1 << blkbits) - 1;
ssize_t retval = -EINVAL;
struct dio *dio;
+ int needs_locking;
if (bdev)
bdev_blkbits = blksize_bits(bdev_hardsect_size(bdev));
@@ -1063,7 +1065,9 @@ blockdev_direct_IO(int rw, struct kiocb
* readers need to grab i_sem and i_alloc_sem
* writers need to grab i_alloc_sem only (i_sem is already held)
*/
- if (S_ISREG(inode->i_mode)) {
+ needs_locking = 0;
+ if (S_ISREG(inode->i_mode) && needs_special_locking) {
+ needs_locking = 1;
if (rw == READ) {
down(&inode->i_sem);
retval = filemap_write_and_wait(inode->i_mapping);
@@ -1075,11 +1079,13 @@ blockdev_direct_IO(int rw, struct kiocb
}
down_read(&inode->i_alloc_sem);
}
+ dio->needs_locking = needs_locking;
retval = direct_io_worker(rw, iocb, inode, iov, offset,
nr_segs, blkbits, get_blocks, end_io, dio);
- if (S_ISREG(inode->i_mode) && rw == WRITE)
+ if (needs_locking && rw == WRITE)
down(&inode->i_sem);
out:
return retval;
}
+EXPORT_SYMBOL(__blockdev_direct_IO);
diff -puN include/linux/fs.h~O_DIRECT-race-fixes-rework-XFS-fix include/linux/fs.h
--- 25/include/linux/fs.h~O_DIRECT-race-fixes-rework-XFS-fix 2003-10-01 20:26:22.000000000 -0700
+++ 25-akpm/include/linux/fs.h 2003-10-01 20:26:22.000000000 -0700
@@ -1316,9 +1316,6 @@ extern void
file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
extern ssize_t generic_file_direct_IO(int rw, struct kiocb *iocb,
const struct iovec *iov, loff_t offset, unsigned long nr_segs);
-extern int blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
- struct block_device *bdev, const struct iovec *iov, loff_t offset,
- unsigned long nr_segs, get_blocks_t *get_blocks, dio_iodone_t *end_io);
extern ssize_t generic_file_readv(struct file *filp, const struct iovec *iov,
unsigned long nr_segs, loff_t *ppos);
ssize_t generic_file_writev(struct file *filp, const struct iovec *iov,
@@ -1340,6 +1337,32 @@ static inline void do_generic_file_read(
actor);
}
+int __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
+ struct block_device *bdev, const struct iovec *iov, loff_t offset,
+ unsigned long nr_segs, get_blocks_t get_blocks, dio_iodone_t end_io,
+ int needs_special_locking);
+
+/*
+ * For filesystems which need locking between buffered and direct access
+ */
+static inline int blockdev_direct_IO(int rw, struct kiocb *iocb,
+ struct inode *inode, struct block_device *bdev, const struct iovec *iov,
+ loff_t offset, unsigned long nr_segs, get_blocks_t get_blocks,
+ dio_iodone_t end_io)
+{
+ return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
+ nr_segs, get_blocks, end_io, 1);
+}
+
+static inline int blockdev_direct_IO_no_locking(int rw, struct kiocb *iocb,
+ struct inode *inode, struct block_device *bdev, const struct iovec *iov,
+ loff_t offset, unsigned long nr_segs, get_blocks_t get_blocks,
+ dio_iodone_t end_io)
+{
+ return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
+ nr_segs, get_blocks, end_io, 0);
+}
+
extern struct file_operations generic_ro_fops;
#define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))
diff -puN fs/xfs/linux/xfs_aops.c~O_DIRECT-race-fixes-rework-XFS-fix fs/xfs/linux/xfs_aops.c
--- 25/fs/xfs/linux/xfs_aops.c~O_DIRECT-race-fixes-rework-XFS-fix 2003-10-01 20:26:22.000000000 -0700
+++ 25-akpm/fs/xfs/linux/xfs_aops.c 2003-10-01 20:26:22.000000000 -0700
@@ -983,7 +983,7 @@ linvfs_direct_IO(
if (error)
return -error;
- return blockdev_direct_IO(rw, iocb, inode,
+ return blockdev_direct_IO_no_locking(rw, iocb, inode,
pbmap.pbm_target->pbr_bdev,
iov, offset, nr_segs,
linvfs_get_blocks_direct,
diff -puN kernel/ksyms.c~O_DIRECT-race-fixes-rework-XFS-fix kernel/ksyms.c
--- 25/kernel/ksyms.c~O_DIRECT-race-fixes-rework-XFS-fix 2003-10-01 20:26:22.000000000 -0700
+++ 25-akpm/kernel/ksyms.c 2003-10-01 20:26:55.000000000 -0700
@@ -157,7 +157,6 @@ EXPORT_SYMBOL(inode_setattr);
EXPORT_SYMBOL(inode_change_ok);
EXPORT_SYMBOL(write_inode_now);
EXPORT_SYMBOL(notify_change);
-EXPORT_SYMBOL(blockdev_direct_IO);
EXPORT_SYMBOL(file_ra_state_init);
EXPORT_SYMBOL(generic_ro_fops);
EXPORT_SYMBOL(get_unused_fd);
_