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use read() for sequential reads on fd #31

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use read() for sequential reads on fd #31

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24 changes: 23 additions & 1 deletion diod/ioctx.c
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,7 @@ struct ioctx_struct {
pthread_mutex_t lock;
int refcount;
int fd;
off_t off;
DIR *dir;
int lock_type;
Npqid qid;
Expand Down Expand Up @@ -181,6 +182,7 @@ _ioctx_create_open (Npuser *user, Path path, int flags, u32 mode)
ioctx->refcount = 1;
ioctx->lock_type = LOCK_UN;
ioctx->dir = NULL;
ioctx->off = 0;
ioctx->open_flags = flags;
ioctx->user = user;
np_user_incref (user);
Expand Down Expand Up @@ -266,7 +268,27 @@ ioctx_open (Npfid *fid, u32 flags, u32 mode)
int
ioctx_pread (IOCtx ioctx, void *buf, size_t count, off_t offset)
{
return pread (ioctx->fd, buf, count, offset);
ssize_t ret;
int has_read = 0;

// claim read() if fd is at this offset
xpthread_mutex_lock (&ioctx->lock);
if (ioctx->off != -1 && ioctx->off == offset) {
ioctx->off = -1;
has_read = 1;
}
xpthread_mutex_unlock (&ioctx->lock);

if (!has_read) {
return pread (ioctx->fd, buf, count, offset);
}
ret = read (ioctx->fd, buf, count);

// next read() operation will follow the end of this one
xpthread_mutex_lock (&ioctx->lock);
ioctx->off = (ret < 0) ? offset : offset + ret;
xpthread_mutex_unlock (&ioctx->lock);
return ret;
}

int
Expand Down