*
* If blkfactor is zero then the user's request was aligned to the filesystem's
* blocksize.
- *
- * lock_type is DIO_LOCKING for regular files on direct-IO-naive filesystems.
- * This determines whether we need to do the fancy locking which prevents
- * direct-IO from being able to read uninitialised disk blocks. If its zero
- * (blockdev) this locking is not done, and if it is DIO_OWN_LOCKING i_mutex is
- * not held for the entire direct write (taken briefly, initially, during a
- * direct read though, but its never held for the duration of a direct-IO).
*/
struct dio {
struct inode *inode;
int rw;
loff_t i_size; /* i_size when submitted */
- int lock_type; /* doesn't change */
+ int flags; /* doesn't change */
unsigned blkbits; /* doesn't change */
unsigned blkfactor; /* When we're using an alignment which
is finer than the filesystem's soft
if (dio->end_io && dio->result)
dio->end_io(dio->iocb, offset, transferred,
dio->map_bh.b_private);
- if (dio->lock_type == DIO_LOCKING)
+
+ if (dio->flags & DIO_LOCKING)
/* lockdep: non-owner release */
up_read_non_owner(&dio->inode->i_alloc_sem);
map_bh->b_state = 0;
map_bh->b_size = fs_count << dio->inode->i_blkbits;
+ /*
+ * For writes inside i_size on a DIO_SKIP_HOLES filesystem we
+ * forbid block creations: only overwrites are permitted.
+ * We will return early to the caller once we see an
+ * unmapped buffer head returned, and the caller will fall
+ * back to buffered I/O.
+ *
+ * Otherwise the decision is left to the get_blocks method,
+ * which may decide to handle it or also return an unmapped
+ * buffer head.
+ */
create = dio->rw & WRITE;
- if (dio->lock_type == DIO_LOCKING) {
+ if (dio->flags & DIO_SKIP_HOLES) {
if (dio->block_in_file < (i_size_read(dio->inode) >>
dio->blkbits))
create = 0;
- } else if (dio->lock_type == DIO_NO_LOCKING) {
- create = 0;
}
- /*
- * For writes inside i_size we forbid block creations: only
- * overwrites are permitted. We fall back to buffered writes
- * at a higher level for inside-i_size block-instantiating
- * writes.
- */
ret = (*dio->get_block)(dio->inode, fs_startblk,
map_bh, create);
}
* we can let i_mutex go now that its achieved its purpose
* of protecting us from looking up uninitialized blocks.
*/
- if ((rw == READ) && (dio->lock_type == DIO_LOCKING))
+ if (rw == READ && (dio->flags & DIO_LOCKING))
mutex_unlock(&dio->inode->i_mutex);
/*
/*
* This is a library function for use by filesystem drivers.
- * The locking rules are governed by the dio_lock_type parameter.
*
- * DIO_NO_LOCKING (no locking, for raw block device access)
- * For writes, i_mutex is not held on entry; it is never taken.
+ * The locking rules are governed by the flags parameter:
+ * - if the flags value contains DIO_LOCKING we use a fancy locking
+ * scheme for dumb filesystems.
+ * For writes this function is called under i_mutex and returns with
+ * i_mutex held, for reads, i_mutex is not held on entry, but it is
+ * taken and dropped again before returning.
+ * For reads and writes i_alloc_sem is taken in shared mode and released
+ * on I/O completion (which may happen asynchronously after returning to
+ * the caller).
*
- * DIO_LOCKING (simple locking for regular files)
- * For writes we are called under i_mutex and return with i_mutex held, even
- * though it is internally dropped.
- * For reads, i_mutex is not held on entry, but it is taken and dropped before
- * returning.
- *
- * DIO_OWN_LOCKING (filesystem provides synchronisation and handling of
- * uninitialised data, allowing parallel direct readers and writers)
- * For writes we are called without i_mutex, return without it, never touch it.
- * For reads we are called under i_mutex and return with i_mutex held, even
- * though it may be internally dropped.
- *
- * Additional i_alloc_sem locking requirements described inline below.
+ * - if the flags value does NOT contain DIO_LOCKING we don't use any
+ * internal locking but rather rely on the filesystem to synchronize
+ * direct I/O reads/writes versus each other and truncate.
+ * For reads and writes both i_mutex and i_alloc_sem are not held on
+ * entry and are never taken.
*/
ssize_t
__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_block_t get_block, dio_iodone_t end_io,
- int dio_lock_type)
+ int flags)
{
int seg;
size_t size;
ssize_t retval = -EINVAL;
loff_t end = offset;
struct dio *dio;
- int release_i_mutex = 0;
- int acquire_i_mutex = 0;
if (rw & WRITE)
rw = WRITE_ODIRECT_PLUG;
if (!dio)
goto out;
- /*
- * For block device access DIO_NO_LOCKING is used,
- * neither readers nor writers do any locking at all
- * For regular files using DIO_LOCKING,
- * readers need to grab i_mutex and i_alloc_sem
- * writers need to grab i_alloc_sem only (i_mutex is already held)
- * For regular files using DIO_OWN_LOCKING,
- * neither readers nor writers take any locks here
- */
- dio->lock_type = dio_lock_type;
- if (dio_lock_type != DIO_NO_LOCKING) {
+ dio->flags = flags;
+ if (dio->flags & DIO_LOCKING) {
/* watch out for a 0 len io from a tricksy fs */
if (rw == READ && end > offset) {
- struct address_space *mapping;
+ struct address_space *mapping =
+ iocb->ki_filp->f_mapping;
- mapping = iocb->ki_filp->f_mapping;
- if (dio_lock_type != DIO_OWN_LOCKING) {
- mutex_lock(&inode->i_mutex);
- release_i_mutex = 1;
- }
+ /* will be released by direct_io_worker */
+ mutex_lock(&inode->i_mutex);
retval = filemap_write_and_wait_range(mapping, offset,
end - 1);
if (retval) {
+ mutex_unlock(&inode->i_mutex);
kfree(dio);
goto out;
}
-
- if (dio_lock_type == DIO_OWN_LOCKING) {
- mutex_unlock(&inode->i_mutex);
- acquire_i_mutex = 1;
- }
}
- if (dio_lock_type == DIO_LOCKING)
- /* lockdep: not the owner will release it */
- down_read_non_owner(&inode->i_alloc_sem);
+ /*
+ * Will be released at I/O completion, possibly in a
+ * different thread.
+ */
+ down_read_non_owner(&inode->i_alloc_sem);
}
/*
/*
* In case of error extending write may have instantiated a few
* blocks outside i_size. Trim these off again for DIO_LOCKING.
- * NOTE: DIO_NO_LOCK/DIO_OWN_LOCK callers have to handle this by
- * it's own meaner.
+ *
+ * NOTE: filesystems with their own locking have to handle this
+ * on their own.
*/
- if (unlikely(retval < 0 && (rw & WRITE))) {
- loff_t isize = i_size_read(inode);
-
- if (end > isize && dio_lock_type == DIO_LOCKING)
- vmtruncate(inode, isize);
+ if (dio->flags & DIO_LOCKING) {
+ if (unlikely((rw & WRITE) && retval < 0)) {
+ loff_t isize = i_size_read(inode);
+ if (end > isize )
+ vmtruncate(inode, isize);
+ }
}
- if (rw == READ && dio_lock_type == DIO_LOCKING)
- release_i_mutex = 0;
-
out:
- if (release_i_mutex)
- mutex_unlock(&inode->i_mutex);
- else if (acquire_i_mutex)
- mutex_lock(&inode->i_mutex);
return retval;
}
EXPORT_SYMBOL(__blockdev_direct_IO);
*
* called like this: dio->get_blocks(dio->inode, fs_startblk,
* fs_count, map_bh, dio->rw == WRITE);
+ *
+ * Note that we never bother to allocate blocks here, and thus ignore the
+ * create argument.
*/
static int ocfs2_direct_IO_get_blocks(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create)
inode_blocks = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode));
- /*
- * Any write past EOF is not allowed because we'd be extending.
- */
- if (create && (iblock + max_blocks) > inode_blocks) {
- ret = -EIO;
- goto bail;
- }
-
/* This figures out the size of the next contiguous block, and
* our logical offset */
ret = ocfs2_extent_map_get_blocks(inode, iblock, &p_blkno,
goto bail;
}
- if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)) && !p_blkno && create) {
- ocfs2_error(inode->i_sb,
- "Inode %llu has a hole at block %llu\n",
- (unsigned long long)OCFS2_I(inode)->ip_blkno,
- (unsigned long long)iblock);
- ret = -EROFS;
- goto bail;
- }
-
/* We should already CoW the refcounted extent. */
BUG_ON(ext_flags & OCFS2_EXT_REFCOUNTED);
/*
*/
if (p_blkno && !(ext_flags & OCFS2_EXT_UNWRITTEN))
map_bh(bh_result, inode->i_sb, p_blkno);
- else {
- /*
- * ocfs2_prepare_inode_for_write() should have caught
- * the case where we'd be filling a hole and triggered
- * a buffered write instead.
- */
- if (create) {
- ret = -EIO;
- mlog_errno(ret);
- goto bail;
- }
-
+ else
clear_buffer_mapped(bh_result);
- }
/* make sure we don't map more than max_blocks blocks here as
that's all the kernel will handle at this point. */
int lock_type);
enum {
- DIO_LOCKING = 1, /* need locking between buffered and direct access */
- DIO_NO_LOCKING, /* bdev; no locking at all between buffered/direct */
- DIO_OWN_LOCKING, /* filesystem locks buffered and direct internally */
+ /* need locking between buffered and direct access */
+ DIO_LOCKING = 0x01,
+
+ /* filesystem does not support filling holes */
+ DIO_SKIP_HOLES = 0x02,
};
static inline ssize_t blockdev_direct_IO(int rw, struct kiocb *iocb,
dio_iodone_t end_io)
{
return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
- nr_segs, get_block, end_io, DIO_LOCKING);
+ nr_segs, get_block, end_io,
+ DIO_LOCKING | DIO_SKIP_HOLES);
}
static inline ssize_t blockdev_direct_IO_no_locking(int rw, struct kiocb *iocb,
dio_iodone_t end_io)
{
return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
- nr_segs, get_block, end_io, DIO_NO_LOCKING);
-}
-
-static inline ssize_t blockdev_direct_IO_own_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_block_t get_block,
- dio_iodone_t end_io)
-{
- return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
- nr_segs, get_block, end_io, DIO_OWN_LOCKING);
+ nr_segs, get_block, end_io, 0);
}
#endif
git.samba.org / sfrench / cifs-2.6.git / commitdiff