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fuse: allow non-extending parallel direct writes on the same file #1

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Merged
merged 1 commit into from
Jun 5, 2023
Merged

fuse: allow non-extending parallel direct writes on the same file #1

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43 changes: 40 additions & 3 deletions fs/fuse/file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1563,14 +1563,47 @@ static ssize_t fuse_direct_read_iter(struct kiocb *iocb, struct iov_iter *to)
return res;
}

static bool fuse_direct_write_extending_i_size(struct kiocb *iocb,
struct iov_iter *iter)
{
struct inode *inode = file_inode(iocb->ki_filp);

return iocb->ki_pos + iov_iter_count(iter) > i_size_read(inode);
}

static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
struct inode *inode = file_inode(iocb->ki_filp);
struct file *file = iocb->ki_filp;
struct fuse_file *ff = file->private_data;
struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
ssize_t res;
bool exclusive_lock =
!(ff->open_flags & FOPEN_PARALLEL_DIRECT_WRITES) ||
iocb->ki_flags & IOCB_APPEND ||
fuse_direct_write_extending_i_size(iocb, from);

/*
* Take exclusive lock if
* - Parallel direct writes are disabled - a user space decision
* - Parallel direct writes are enabled and i_size is being extended.
* This might not be needed at all, but needs further investigation.
*/
if (exclusive_lock)
inode_lock(inode);
else {
inode_lock_shared(inode);

/* A race with truncate might have come up as the decision for
* the lock type was done without holding the lock, check again.
*/
if (fuse_direct_write_extending_i_size(iocb, from)) {
inode_unlock_shared(inode);
inode_lock(inode);
exclusive_lock = true;
}
}

/* Don't allow parallel writes to the same file */
inode_lock(inode);
res = generic_write_checks(iocb, from);
if (res > 0) {
if (!is_sync_kiocb(iocb) && iocb->ki_flags & IOCB_DIRECT) {
Expand All @@ -1581,7 +1614,10 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
fuse_write_update_attr(inode, iocb->ki_pos, res);
}
}
inode_unlock(inode);
if (exclusive_lock)
inode_unlock(inode);
else
inode_unlock_shared(inode);

return res;
}
Expand Down Expand Up @@ -2938,6 +2974,7 @@ fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter)

if (iov_iter_rw(iter) == WRITE) {
fuse_write_update_attr(inode, pos, ret);
/* For extending writes we already hold exclusive lock */
if (ret < 0 && offset + count > i_size)
fuse_do_truncate(file);
}
Expand Down
2 changes: 2 additions & 0 deletions include/uapi/linux/fuse.h
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Original file line number Diff line number Diff line change
Expand Up @@ -302,13 +302,15 @@ struct fuse_file_lock {
* FOPEN_STREAM: the file is stream-like (no file position at all)
* FOPEN_NOFLUSH: don't flush data cache on close (unless FUSE_WRITEBACK_CACHE)
* FOPEN_FILE_CREATED: the file was indeed created
* FOPEN_PARALLEL_DIRECT_WRITES: Allow concurrent direct writes on the same inode
*/
#define FOPEN_DIRECT_IO (1 << 0)
#define FOPEN_KEEP_CACHE (1 << 1)
#define FOPEN_NONSEEKABLE (1 << 2)
#define FOPEN_CACHE_DIR (1 << 3)
#define FOPEN_STREAM (1 << 4)
#define FOPEN_NOFLUSH (1 << 5)
#define FOPEN_PARALLEL_DIRECT_WRITES (1 << 6)
#define FOPEN_FILE_CREATED (1 << 7)

/**
Expand Down