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authorJan Kara <jack@suse.cz>2009-08-17 18:10:06 +0200
committerJan Kara <jack@suse.cz>2009-09-14 17:08:14 +0200
commite4dd9de3c66bc7e26c5c7f149a060c5a67cf06a0 (patch)
tree3270180b085c86afe4834fba5567464cd3932eb8 /mm/filemap.c
parentd3bccb6f4b886060aa0f58976b92b77d951f5434 (diff)
downloadconfigs-e4dd9de3c66bc7e26c5c7f149a060c5a67cf06a0.tar.gz
vfs: Export __generic_file_aio_write() and add some comments
Rename __generic_file_aio_write_nolock() to __generic_file_aio_write(), add comments to write helpers explaining how they should be used and export __generic_file_aio_write() since it will be used by some filesystems. CC: ocfs2-devel@oss.oracle.com CC: Joel Becker <joel.becker@oracle.com> Acked-by: Evgeniy Polyakov <zbr@ioremap.net> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'mm/filemap.c')
-rw-r--r--mm/filemap.c57
1 files changed, 50 insertions, 7 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 65b2e50efcd..554a396d85e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2368,9 +2368,27 @@ generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
}
EXPORT_SYMBOL(generic_file_buffered_write);
-static ssize_t
-__generic_file_aio_write_nolock(struct kiocb *iocb, const struct iovec *iov,
- unsigned long nr_segs, loff_t *ppos)
+/**
+ * __generic_file_aio_write - write data to a file
+ * @iocb: IO state structure (file, offset, etc.)
+ * @iov: vector with data to write
+ * @nr_segs: number of segments in the vector
+ * @ppos: position where to write
+ *
+ * This function does all the work needed for actually writing data to a
+ * file. It does all basic checks, removes SUID from the file, updates
+ * modification times and calls proper subroutines depending on whether we
+ * do direct IO or a standard buffered write.
+ *
+ * It expects i_mutex to be grabbed unless we work on a block device or similar
+ * object which does not need locking at all.
+ *
+ * This function does *not* take care of syncing data in case of O_SYNC write.
+ * A caller has to handle it. This is mainly due to the fact that we want to
+ * avoid syncing under i_mutex.
+ */
+ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
+ unsigned long nr_segs, loff_t *ppos)
{
struct file *file = iocb->ki_filp;
struct address_space * mapping = file->f_mapping;
@@ -2467,7 +2485,23 @@ out:
current->backing_dev_info = NULL;
return written ? written : err;
}
+EXPORT_SYMBOL(__generic_file_aio_write);
+
+/**
+ * generic_file_aio_write_nolock - write data, usually to a device
+ * @iocb: IO state structure
+ * @iov: vector with data to write
+ * @nr_segs: number of segments in the vector
+ * @pos: position in file where to write
+ *
+ * This is a wrapper around __generic_file_aio_write() which takes care of
+ * syncing the file in case of O_SYNC file. It does not take i_mutex for the
+ * write itself but may do so during syncing. It is meant for users like block
+ * devices which do not need i_mutex during write. If your filesystem needs to
+ * do a write but already holds i_mutex, use __generic_file_aio_write()
+ * directly and then sync the file like generic_file_aio_write().
+ */
ssize_t generic_file_aio_write_nolock(struct kiocb *iocb,
const struct iovec *iov, unsigned long nr_segs, loff_t pos)
{
@@ -2478,8 +2512,7 @@ ssize_t generic_file_aio_write_nolock(struct kiocb *iocb,
BUG_ON(iocb->ki_pos != pos);
- ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
- &iocb->ki_pos);
+ ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
ssize_t err;
@@ -2492,6 +2525,17 @@ ssize_t generic_file_aio_write_nolock(struct kiocb *iocb,
}
EXPORT_SYMBOL(generic_file_aio_write_nolock);
+/**
+ * generic_file_aio_write - write data to a file
+ * @iocb: IO state structure
+ * @iov: vector with data to write
+ * @nr_segs: number of segments in the vector
+ * @pos: position in file where to write
+ *
+ * This is a wrapper around __generic_file_aio_write() to be used by most
+ * filesystems. It takes care of syncing the file in case of O_SYNC file
+ * and acquires i_mutex as needed.
+ */
ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
unsigned long nr_segs, loff_t pos)
{
@@ -2503,8 +2547,7 @@ ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
BUG_ON(iocb->ki_pos != pos);
mutex_lock(&inode->i_mutex);
- ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
- &iocb->ki_pos);
+ ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
mutex_unlock(&inode->i_mutex);
if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {